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Add overlay for JEDEC SPI NOR flash
[mirror_ubuntu-bionic-kernel.git] / arch / arm / boot / dts / overlays / README
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2f060b25 1Introduction
2============
3
4This directory contains Device Tree overlays. Device Tree makes it possible
5to support many hardware configurations with a single kernel and without the
6need to explicitly load or blacklist kernel modules. Note that this isn't a
7"pure" Device Tree configuration (c.f. MACH_BCM2835) - some on-board devices
8are still configured by the board support code, but the intention is to
9eventually reach that goal.
10
11On Raspberry Pi, Device Tree usage is controlled from /boot/config.txt. By
12default, the Raspberry Pi kernel boots with device tree enabled. You can
13completely disable DT usage (for now) by adding:
14
15 device_tree=
16
17to your config.txt, which should cause your Pi to revert to the old way of
18doing things after a reboot.
19
20In /boot you will find a .dtb for each base platform. This describes the
21hardware that is part of the Raspberry Pi board. The loader (start.elf and its
22siblings) selects the .dtb file appropriate for the platform by name, and reads
23it into memory. At this point, all of the optional interfaces (i2c, i2s, spi)
24are disabled, but they can be enabled using Device Tree parameters:
25
26 dtparam=i2c=on,i2s=on,spi=on
27
28However, this shouldn't be necessary in many use cases because loading an
29overlay that requires one of those interfaces will cause it to be enabled
30automatically, and it is advisable to only enable interfaces if they are
31needed.
32
33Configuring additional, optional hardware is done using Device Tree overlays
34(see below).
35
36GPIO numbering uses the hardware pin numbering scheme (aka BCM scheme) and
37not the physical pin numbers.
38
39raspi-config
40============
41
42The Advanced Options section of the raspi-config utility can enable and disable
43Device Tree use, as well as toggling the I2C and SPI interfaces. Note that it
44is possible to both enable an interface and blacklist the driver, if for some
45reason you should want to defer the loading.
46
47Modules
48=======
49
50As well as describing the hardware, Device Tree also gives enough information
51to allow suitable driver modules to be located and loaded, with the corollary
52that unneeded modules are not loaded. As a result it should be possible to
53remove lines from /etc/modules, and /etc/modprobe.d/raspi-blacklist.conf can
54have its contents deleted (or commented out).
55
56Using Overlays
57==============
58
59Overlays are loaded using the "dtoverlay" directive. As an example, consider
60the popular lirc-rpi module, the Linux Infrared Remote Control driver. In the
61pre-DT world this would be loaded from /etc/modules, with an explicit
62"modprobe lirc-rpi" command, or programmatically by lircd. With DT enabled,
63this becomes a line in config.txt:
64
65 dtoverlay=lirc-rpi
66
67This causes the file /boot/overlays/lirc-rpi.dtbo to be loaded. By
68default it will use GPIOs 17 (out) and 18 (in), but this can be modified using
69DT parameters:
70
71 dtoverlay=lirc-rpi,gpio_out_pin=17,gpio_in_pin=13
72
73Parameters always have default values, although in some cases (e.g. "w1-gpio")
74it is necessary to provided multiple overlays in order to get the desired
75behaviour. See the list of overlays below for a description of the parameters
76and their defaults.
77
78The Overlay and Parameter Reference
79===================================
80
81N.B. When editing this file, please preserve the indentation levels to make it
82simple to parse programmatically. NO HARD TABS.
83
84
85Name: <The base DTB>
86Info: Configures the base Raspberry Pi hardware
87Load: <loaded automatically>
88Params:
89 audio Set to "on" to enable the onboard ALSA audio
90 interface (default "off")
91
e4078e86
PE		 92 eee Enable Energy Efficient Ethernet support for
93 compatible devices (default "on"). See also
94 "tx_lpi_timer".
95
b8dfb6db
PE		 96 eth_led0 Set mode of LED0 (usually orange) (default
97 "1"). The legal values are:
98 0=link/activity 1=link1000/activity
99 2=link100/activity 3=link10/activity
100 4=link100/1000/activity 5=link10/1000/activity
101 6=link10/100/activity 14=off 15=on
102
103 eth_led1 Set mode of LED1 (usually green) (default
104 "6"). See eth_led0 for legal values.
105
2f060b25 106 i2c_arm Set to "on" to enable the ARM's i2c interface
107 (default "off")
108
109 i2c_vc Set to "on" to enable the i2c interface
110 usually reserved for the VideoCore processor
111 (default "off")
112
113 i2c An alias for i2c_arm
114
115 i2c_arm_baudrate Set the baudrate of the ARM's i2c interface
116 (default "100000")
117
118 i2c_vc_baudrate Set the baudrate of the VideoCore i2c interface
119 (default "100000")
120
121 i2c_baudrate An alias for i2c_arm_baudrate
122
123 i2s Set to "on" to enable the i2s interface
124 (default "off")
125
126 spi Set to "on" to enable the spi interfaces
127 (default "off")
128
129 random Set to "on" to enable the hardware random
130 number generator (default "on")
131
132 sd_overclock Clock (in MHz) to use when the MMC framework
133 requests 50MHz
134
135 sd_force_pio Disable DMA support for SD driver (default off)
136
137 sd_pio_limit Number of blocks above which to use DMA for
138 SD card (default 1)
139
140 sd_debug Enable debug output from SD driver (default off)
141
e4078e86
PE		 142 tx_lpi_timer Set the delay in microseconds between going idle
143 and entering the low power state (default 600).
144 Requires EEE to be enabled - see "eee".
145
2f060b25 146 uart0 Set to "off" to disable uart0 (default "on")
147
148 uart1 Set to "on" or "off" to enable or disable uart1
149 (default varies)
150
151 watchdog Set to "on" to enable the hardware watchdog
152 (default "off")
153
154 act_led_trigger Choose which activity the LED tracks.
155 Use "heartbeat" for a nice load indicator.
156 (default "mmc")
157
158 act_led_activelow Set to "on" to invert the sense of the LED
159 (default "off")
160 N.B. For Pi3 see pi3-act-led overlay.
161
162 act_led_gpio Set which GPIO to use for the activity LED
163 (in case you want to connect it to an external
164 device)
165 (default "16" on a non-Plus board, "47" on a
166 Plus or Pi 2)
167 N.B. For Pi3 see pi3-act-led overlay.
168
169 pwr_led_trigger
170 pwr_led_activelow
171 pwr_led_gpio
172 As for act_led_*, but using the PWR LED.
173 Not available on Model A/B boards.
174
175 N.B. It is recommended to only enable those interfaces that are needed.
176 Leaving all interfaces enabled can lead to unwanted behaviour (i2c_vc
177 interfering with Pi Camera, I2S and SPI hogging GPIO pins, etc.)
178 Note also that i2c, i2c_arm and i2c_vc are aliases for the physical
179 interfaces i2c0 and i2c1. Use of the numeric variants is still possible
180 but deprecated because the ARM/VC assignments differ between board
181 revisions. The same board-specific mapping applies to i2c_baudrate,
182 and the other i2c baudrate parameters.
183
184
185Name: adau1977-adc
186Info: Overlay for activation of ADAU1977 ADC codec over I2C for control
187 and I2S for data.
188Load: dtoverlay=adau1977-adc
189Params: <None>
190
191
192Name: adau7002-simple
193Info: Overlay for the activation of ADAU7002 stereo PDM to I2S converter.
194Load: dtoverlay=adau7002-simple,<param>=<val>
195Params: card-name Override the default, "adau7002", card name.
196
197
198Name: ads1015
199Info: Overlay for activation of Texas Instruments ADS1015 ADC over I2C
200Load: dtoverlay=ads1015,<param>=<val>
201Params: addr I2C bus address of device. Set based on how the
202 addr pin is wired. (default=0x48 assumes addr
203 is pulled to GND)
204 cha_enable Enable virtual channel a. (default=true)
205 cha_cfg Set the configuration for virtual channel a.
206 (default=4 configures this channel for the
207 voltage at A0 with respect to GND)
208 cha_datarate Set the datarate (samples/sec) for this channel.
209 (default=4 sets 1600 sps)
210 cha_gain Set the gain of the Programmable Gain
211 Amplifier for this channel. (default=2 sets the
212 full scale of the channel to 2.048 Volts)
213
214 Channel (ch) parameters can be set for each enabled channel.
215 A maximum of 4 channels can be enabled (letters a thru d).
216 For more information refer to the device datasheet at:
217 http://www.ti.com/lit/ds/symlink/ads1015.pdf
218
219
220Name: ads1115
221Info: Texas Instruments ADS1115 ADC
222Load: dtoverlay=ads1115,<param>[=<val>]
223Params: addr I2C bus address of device. Set based on how the
224 addr pin is wired. (default=0x48 assumes addr
225 is pulled to GND)
226 cha_enable Enable virtual channel a.
227 cha_cfg Set the configuration for virtual channel a.
228 (default=4 configures this channel for the
229 voltage at A0 with respect to GND)
230 cha_datarate Set the datarate (samples/sec) for this channel.
231 (default=7 sets 860 sps)
232 cha_gain Set the gain of the Programmable Gain
233 Amplifier for this channel. (Default 1 sets the
234 full scale of the channel to 4.096 Volts)
235
236 Channel parameters can be set for each enabled channel.
237 A maximum of 4 channels can be enabled (letters a thru d).
238 For more information refer to the device datasheet at:
239 http://www.ti.com/lit/ds/symlink/ads1115.pdf
240
241
242Name: ads7846
243Info: ADS7846 Touch controller
244Load: dtoverlay=ads7846,<param>=<val>
245Params: cs SPI bus Chip Select (default 1)
246 speed SPI bus speed (default 2MHz, max 3.25MHz)
247 penirq GPIO used for PENIRQ. REQUIRED
248 penirq_pull Set GPIO pull (default 0=none, 2=pullup)
249 swapxy Swap x and y axis
250 xmin Minimum value on the X axis (default 0)
251 ymin Minimum value on the Y axis (default 0)
252 xmax Maximum value on the X axis (default 4095)
253 ymax Maximum value on the Y axis (default 4095)
254 pmin Minimum reported pressure value (default 0)
255 pmax Maximum reported pressure value (default 65535)
256 xohms Touchpanel sensitivity (X-plate resistance)
257 (default 400)
258
259 penirq is required and usually xohms (60-100) has to be set as well.
260 Apart from that, pmax (255) and swapxy are also common.
261 The rest of the calibration can be done with xinput-calibrator.
262 See: github.com/notro/fbtft/wiki/FBTFT-on-Raspian
263 Device Tree binding document:
264 www.kernel.org/doc/Documentation/devicetree/bindings/input/ads7846.txt
265
266
267Name: akkordion-iqdacplus
268Info: Configures the Digital Dreamtime Akkordion Music Player (based on the
269 OEM IQAudIO DAC+ or DAC Zero module).
270Load: dtoverlay=akkordion-iqdacplus,<param>=<val>
271Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
272 Digital volume control. Enable with
273 dtoverlay=akkordion-iqdacplus,24db_digital_gain
274 (The default behaviour is that the Digital
275 volume control is limited to a maximum of
276 0dB. ie. it can attenuate but not provide
277 gain. For most users, this will be desired
278 as it will prevent clipping. By appending
279 the 24db_digital_gain parameter, the Digital
280 volume control will allow up to 24dB of
281 gain. If this parameter is enabled, it is the
282 responsibility of the user to ensure that
283 the Digital volume control is set to a value
284 that does not result in clipping/distortion!)
285
286
287Name: allo-boss-dac-pcm512x-audio
288Info: Configures the Allo Boss DAC audio cards.
289Load: dtoverlay=allo-boss-dac-pcm512x-audio,<param>
290Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
291 Digital volume control. Enable with
292 "dtoverlay=allo-boss-dac-pcm512x-audio,
293 24db_digital_gain"
294 (The default behaviour is that the Digital
295 volume control is limited to a maximum of
296 0dB. ie. it can attenuate but not provide
297 gain. For most users, this will be desired
298 as it will prevent clipping. By appending
299 the 24db_digital_gain parameter, the Digital
300 volume control will allow up to 24dB of
301 gain. If this parameter is enabled, it is the
302 responsibility of the user to ensure that
303 the Digital volume control is set to a value
304 that does not result in clipping/distortion!)
305 slave Force Boss DAC into slave mode, using Pi a
306 master for bit clock and frame clock. Enable
307 with "dtoverlay=allo-boss-dac-pcm512x-audio,
308 slave"
309
310
311Name: allo-digione
312Info: Configures the Allo Digione audio card
313Load: dtoverlay=allo-digione
314Params: <None>
315
316
317Name: allo-piano-dac-pcm512x-audio
318Info: Configures the Allo Piano DAC (2.0/2.1) audio cards.
319 (NB. This initial support is for 2.0 channel audio ONLY! ie. stereo.
320 The subwoofer outputs on the Piano 2.1 are not currently supported!)
321Load: dtoverlay=allo-piano-dac-pcm512x-audio,<param>
322Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
323 Digital volume control.
324 (The default behaviour is that the Digital
325 volume control is limited to a maximum of
326 0dB. ie. it can attenuate but not provide
327 gain. For most users, this will be desired
328 as it will prevent clipping. By appending
329 the 24db_digital_gain parameter, the Digital
330 volume control will allow up to 24dB of
331 gain. If this parameter is enabled, it is the
332 responsibility of the user to ensure that
333 the Digital volume control is set to a value
334 that does not result in clipping/distortion!)
335
336
337Name: allo-piano-dac-plus-pcm512x-audio
338Info: Configures the Allo Piano DAC (2.1) audio cards.
339Load: dtoverlay=allo-piano-dac-plus-pcm512x-audio,<param>
340Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
341 Digital volume control.
342 (The default behaviour is that the Digital
343 volume control is limited to a maximum of
344 0dB. ie. it can attenuate but not provide
345 gain. For most users, this will be desired
346 as it will prevent clipping. By appending
347 the 24db_digital_gain parameter, the Digital
348 volume control will allow up to 24dB of
349 gain. If this parameter is enabled, it is the
350 responsibility of the user to ensure that
351 the Digital volume control is set to a value
352 that does not result in clipping/distortion!)
353 glb_mclk This option is only with Kali board. If enabled,
354 MCLK for Kali is used and PLL is disabled for
355 better voice quality. (default Off)
356
357
358Name: applepi-dac
359Info: Configures the Orchard Audio ApplePi-DAC audio card
360Load: dtoverlay=applepi-dac
361Params: <None>
362
363
364Name: at86rf233
365Info: Configures the Atmel AT86RF233 802.15.4 low-power WPAN transceiver,
366 connected to spi0.0
367Load: dtoverlay=at86rf233,<param>=<val>
368Params: interrupt GPIO used for INT (default 23)
369 reset GPIO used for Reset (default 24)
370 sleep GPIO used for Sleep (default 25)
371 speed SPI bus speed in Hz (default 3000000)
372 trim Fine tuning of the internal capacitance
373 arrays (0=+0pF, 15=+4.5pF, default 15)
374
375
376Name: audioinjector-addons
377Info: Configures the audioinjector.net audio add on soundcards
4da52c6d
PE		 378Load: dtoverlay=audioinjector-addons,<param>=<val>
379Params: non-stop-clocks Keeps the clocks running even when the stream
380 is paused or stopped (default off)
2f060b25 381
382
383Name: audioinjector-wm8731-audio
384Info: Configures the audioinjector.net audio add on soundcard
385Load: dtoverlay=audioinjector-wm8731-audio
386Params: <None>
387
388
389Name: audremap
390Info: Switches PWM sound output to pins 12 (Right) & 13 (Left)
391Load: dtoverlay=audremap,<param>=<val>
392Params: swap_lr Reverse the channel allocation, which will also
393 swap the audio jack outputs (default off)
394 enable_jack Don't switch off the audio jack output
395 (default off)
396
397
398Name: bmp085_i2c-sensor
399Info: This overlay is now deprecated - see i2c-sensor
400Load: dtoverlay=bmp085_i2c-sensor
401Params: <None>
402
403
404Name: dht11
405Info: Overlay for the DHT11/DHT21/DHT22 humidity/temperature sensors
406 Also sometimes found with the part number(s) AM230x.
407Load: dtoverlay=dht11,<param>=<val>
408Params: gpiopin GPIO connected to the sensor's DATA output.
409 (default 4)
410
411
412Name: dionaudio-loco
413Info: Configures the Dion Audio LOCO DAC-AMP
414Load: dtoverlay=dionaudio-loco
415Params: <None>
416
417
418Name: dionaudio-loco-v2
419Info: Configures the Dion Audio LOCO-V2 DAC-AMP
420Load: dtoverlay=dionaudio-loco-v2,<param>=<val>
421Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
422 Digital volume control. Enable with
423 "dtoverlay=hifiberry-dacplus,24db_digital_gain"
424 (The default behaviour is that the Digital
425 volume control is limited to a maximum of
426 0dB. ie. it can attenuate but not provide
427 gain. For most users, this will be desired
428 as it will prevent clipping. By appending
429 the 24dB_digital_gain parameter, the Digital
430 volume control will allow up to 24dB of
431 gain. If this parameter is enabled, it is the
432 responsibility of the user to ensure that
433 the Digital volume control is set to a value
434 that does not result in clipping/distortion!)
435
436
437Name: dpi18
438Info: Overlay for a generic 18-bit DPI display
439 This uses GPIOs 0-21 (so no I2C, uart etc.), and activates the output
440 2-3 seconds after the kernel has started.
441Load: dtoverlay=dpi18
442Params: <None>
443
444
445Name: dpi24
446Info: Overlay for a generic 24-bit DPI display
447 This uses GPIOs 0-27 (so no I2C, uart etc.), and activates the output
448 2-3 seconds after the kernel has started.
449Load: dtoverlay=dpi24
450Params: <None>
451
452
453Name: dwc-otg
454Info: Selects the dwc_otg USB controller driver which has fiq support. This
455 is the default on all except the Pi Zero which defaults to dwc2.
456Load: dtoverlay=dwc-otg
457Params: <None>
458
459
460Name: dwc2
461Info: Selects the dwc2 USB controller driver
462Load: dtoverlay=dwc2,<param>=<val>
463Params: dr_mode Dual role mode: "host", "peripheral" or "otg"
464
465 g-rx-fifo-size Size of rx fifo size in gadget mode
466
467 g-np-tx-fifo-size Size of non-periodic tx fifo size in gadget
468 mode
469
470
471[ The ds1307-rtc overlay has been deleted. See i2c-rtc. ]
472
473
474Name: enc28j60
475Info: Overlay for the Microchip ENC28J60 Ethernet Controller on SPI0
476Load: dtoverlay=enc28j60,<param>=<val>
477Params: int_pin GPIO used for INT (default 25)
478
479 speed SPI bus speed (default 12000000)
480
481
482Name: enc28j60-spi2
483Info: Overlay for the Microchip ENC28J60 Ethernet Controller on SPI2
484Load: dtoverlay=enc28j60-spi2,<param>=<val>
485Params: int_pin GPIO used for INT (default 39)
486
487 speed SPI bus speed (default 12000000)
488
489
490Name: exc3000
491Info: Enables I2C connected EETI EXC3000 multiple touch controller using
492 GPIO 4 (pin 7 on GPIO header) for interrupt.
493Load: dtoverlay=exc3000,<param>=<val>
494Params: interrupt GPIO used for interrupt (default 4)
495 sizex Touchscreen size x (default 4096)
496 sizey Touchscreen size y (default 4096)
497 invx Touchscreen inverted x axis
498 invy Touchscreen inverted y axis
499 swapxy Touchscreen swapped x y axis
500
501
502Name: fe-pi-audio
503Info: Configures the Fe-Pi Audio Sound Card
504Load: dtoverlay=fe-pi-audio
505Params: <None>
506
507
508Name: goodix
509Info: Enables I2C connected Goodix gt9271 multiple touch controller using
510 GPIOs 4 and 17 (pins 7 and 11 on GPIO header) for interrupt and reset.
511Load: dtoverlay=goodix,<param>=<val>
512Params: interrupt GPIO used for interrupt (default 4)
513 reset GPIO used for reset (default 17)
514
515
516Name: googlevoicehat-soundcard
517Info: Configures the Google voiceHAT soundcard
518Load: dtoverlay=googlevoicehat-soundcard
519Params: <None>
520
521
522Name: gpio-ir
523Info: Use GPIO pin as rc-core style infrared receiver input. The rc-core-
524 based gpio_ir_recv driver maps received keys directly to a
525 /dev/input/event* device, all decoding is done by the kernel - LIRC is
526 not required! The key mapping and other decoding parameters can be
527 configured by "ir-keytable" tool.
528Load: dtoverlay=gpio-ir,<param>=<val>
529Params: gpio_pin Input pin number. Default is 18.
530
531 gpio_pull Desired pull-up/down state (off, down, up)
532 Default is "down".
533
534 rc-map-name Default rc keymap (can also be changed by
535 ir-keytable), defaults to "rc-rc6-mce"
536
537
538Name: gpio-ir-tx
539Info: Use GPIO pin as bit-banged infrared transmitter output.
540 This is an alternative to "pwm-ir-tx". gpio-ir-tx doesn't require
541 a PWM so it can be used together with onboard analog audio.
542Load: dtoverlay=gpio-ir-tx,<param>=<val>
543Params: gpio_pin Output GPIO (default 18)
544
545 invert "1" = invert the output (make it active-low).
546 Default is "0" (active-high).
547
548
549Name: gpio-key
550Info: This is a generic overlay for activating GPIO keypresses using
551 the gpio-keys library and this dtoverlay. Multiple keys can be
552 set up using multiple calls to the overlay for configuring
553 additional buttons or joysticks. You can see available keycodes
554 at https://github.com/torvalds/linux/blob/v4.12/include/uapi/
555 linux/input-event-codes.h#L64
556Load: dtoverlay=gpio-key,<param>=<val>
557Params: gpio GPIO pin to trigger on (default 3)
558 active_low When this is 1 (active low), a falling
559 edge generates a key down event and a
560 rising edge generates a key up event.
561 When this is 0 (active high), this is
562 reversed. The default is 1 (active low)
563 gpio_pull Desired pull-up/down state (off, down, up)
564 Default is "up". Note that the default pin
565 (GPIO3) has an external pullup
566 label Set a label for the key
567 keycode Set the key code for the button
568
569
570Name: gpio-poweroff
571Info: Drives a GPIO high or low on poweroff (including halt). Enabling this
572 overlay will prevent the ability to boot by driving GPIO3 low.
573Load: dtoverlay=gpio-poweroff,<param>=<val>
574Params: gpiopin GPIO for signalling (default 26)
575
576 active_low Set if the power control device requires a
577 high->low transition to trigger a power-down.
578 Note that this will require the support of a
579 custom dt-blob.bin to prevent a power-down
580 during the boot process, and that a reboot
581 will also cause the pin to go low.
582
583
584Name: gpio-shutdown
585Info: Initiates a shutdown when GPIO pin changes. The given GPIO pin
586 is configured as an input key that generates KEY_POWER events.
587 This event is handled by systemd-logind by initiating a
588 shutdown. Systemd versions older than 225 need an udev rule
589 enable listening to the input device:
590
591 ACTION!="REMOVE", SUBSYSTEM=="input", KERNEL=="event*", \
592 SUBSYSTEMS=="platform", DRIVERS=="gpio-keys", \
593 ATTRS{keys}=="116", TAG+="power-switch"
594
595 This overlay only handles shutdown. After shutdown, the system
596 can be powered up again by driving GPIO3 low. The default
597 configuration uses GPIO3 with a pullup, so if you connect a
598 button between GPIO3 and GND (pin 5 and 6 on the 40-pin header),
599 you get a shutdown and power-up button.
600Load: dtoverlay=gpio-shutdown,<param>=<val>
601Params: gpio_pin GPIO pin to trigger on (default 3)
602
603 active_low When this is 1 (active low), a falling
604 edge generates a key down event and a
605 rising edge generates a key up event.
606 When this is 0 (active high), this is
607 reversed. The default is 1 (active low).
608
609 gpio_pull Desired pull-up/down state (off, down, up)
610 Default is "up".
611
612 Note that the default pin (GPIO3) has an
613 external pullup.
614
615
616Name: hifiberry-amp
617Info: Configures the HifiBerry Amp and Amp+ audio cards
618Load: dtoverlay=hifiberry-amp
619Params: <None>
620
621
622Name: hifiberry-dac
623Info: Configures the HifiBerry DAC audio card
624Load: dtoverlay=hifiberry-dac
625Params: <None>
626
627
628Name: hifiberry-dacplus
629Info: Configures the HifiBerry DAC+ audio card
630Load: dtoverlay=hifiberry-dacplus,<param>=<val>
631Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
632 Digital volume control. Enable with
633 "dtoverlay=hifiberry-dacplus,24db_digital_gain"
634 (The default behaviour is that the Digital
635 volume control is limited to a maximum of
636 0dB. ie. it can attenuate but not provide
637 gain. For most users, this will be desired
638 as it will prevent clipping. By appending
639 the 24dB_digital_gain parameter, the Digital
640 volume control will allow up to 24dB of
641 gain. If this parameter is enabled, it is the
642 responsibility of the user to ensure that
643 the Digital volume control is set to a value
644 that does not result in clipping/distortion!)
645 slave Force DAC+ Pro into slave mode, using Pi as
646 master for bit clock and frame clock.
647
648
649Name: hifiberry-digi
650Info: Configures the HifiBerry Digi and Digi+ audio card
651Load: dtoverlay=hifiberry-digi
652Params: <None>
653
654
655Name: hifiberry-digi-pro
656Info: Configures the HifiBerry Digi+ Pro audio card
657Load: dtoverlay=hifiberry-digi-pro
658Params: <None>
659
660
661Name: hy28a
662Info: HY28A - 2.8" TFT LCD Display Module by HAOYU Electronics
663 Default values match Texy's display shield
664Load: dtoverlay=hy28a,<param>=<val>
665Params: speed Display SPI bus speed
666
667 rotate Display rotation {0,90,180,270}
668
669 fps Delay between frame updates
670
671 debug Debug output level {0-7}
672
673 xohms Touchpanel sensitivity (X-plate resistance)
674
675 resetgpio GPIO used to reset controller
676
677 ledgpio GPIO used to control backlight
678
679
680Name: hy28b
681Info: HY28B - 2.8" TFT LCD Display Module by HAOYU Electronics
682 Default values match Texy's display shield
683Load: dtoverlay=hy28b,<param>=<val>
684Params: speed Display SPI bus speed
685
686 rotate Display rotation {0,90,180,270}
687
688 fps Delay between frame updates
689
690 debug Debug output level {0-7}
691
692 xohms Touchpanel sensitivity (X-plate resistance)
693
694 resetgpio GPIO used to reset controller
695
696 ledgpio GPIO used to control backlight
697
698
699Name: i2c-bcm2708
700Info: Fall back to the i2c_bcm2708 driver for the i2c_arm bus.
701Load: dtoverlay=i2c-bcm2708
702Params: <None>
703
704
705Name: i2c-gpio
706Info: Adds support for software i2c controller on gpio pins
707Load: dtoverlay=i2c-gpio,<param>=<val>
708Params: i2c_gpio_sda GPIO used for I2C data (default "23")
709
710 i2c_gpio_scl GPIO used for I2C clock (default "24")
711
712 i2c_gpio_delay_us Clock delay in microseconds
713 (default "2" = ~100kHz)
714
7f4f360f 715 bus Set to a unique, non-zero value if wanting
825ddff8
PE		 716 multiple i2c-gpio busses. If set, will be used
717 as the preferred bus number (/dev/i2c-<n>). If
718 not set, the default value is 0, but the bus
719 number will be dynamically assigned - probably
720 3.
7f4f360f 721
2f060b25 722
723Name: i2c-mux
724Info: Adds support for a number of I2C bus multiplexers on i2c_arm
725Load: dtoverlay=i2c-mux,<param>=<val>
726Params: pca9542 Select the NXP PCA9542 device
727
728 pca9545 Select the NXP PCA9545 device
729
730 pca9548 Select the NXP PCA9548 device
731
732 addr Change I2C address of the device (default 0x70)
733
734
735[ The i2c-mux-pca9548a overlay has been deleted. See i2c-mux. ]
736
737
738Name: i2c-pwm-pca9685a
739Info: Adds support for an NXP PCA9685A I2C PWM controller on i2c_arm
740Load: dtoverlay=i2c-pwm-pca9685a,<param>=<val>
741Params: addr I2C address of PCA9685A (default 0x40)
742
743
744Name: i2c-rtc
745Info: Adds support for a number of I2C Real Time Clock devices
746Load: dtoverlay=i2c-rtc,<param>=<val>
747Params: abx80x Select one of the ABx80x family:
748 AB0801, AB0803, AB0804, AB0805,
749 AB1801, AB1803, AB1804, AB1805
750
751 ds1307 Select the DS1307 device
752
753 ds1339 Select the DS1339 device
754
755 ds3231 Select the DS3231 device
756
757 m41t62 Select the M41T62 device
758
759 mcp7940x Select the MCP7940x device
760
761 mcp7941x Select the MCP7941x device
762
763 pcf2127 Select the PCF2127 device
764
765 pcf8523 Select the PCF8523 device
766
767 pcf8563 Select the PCF8563 device
768
769 trickle-diode-type Diode type for trickle charge - "standard" or
770 "schottky" (ABx80x only)
771
772 trickle-resistor-ohms Resistor value for trickle charge (DS1339,
773 ABx80x)
774
775 wakeup-source Specify that the RTC can be used as a wakeup
776 source
777
778
779Name: i2c-rtc-gpio
780Info: Adds support for a number of I2C Real Time Clock devices
781 using the software i2c controller
782Load: dtoverlay=i2c-rtc-gpio,<param>=<val>
783Params: abx80x Select one of the ABx80x family:
784 AB0801, AB0803, AB0804, AB0805,
785 AB1801, AB1803, AB1804, AB1805
786
787 ds1307 Select the DS1307 device
788
789 ds1339 Select the DS1339 device
790
791 ds3231 Select the DS3231 device
792
793 mcp7940x Select the MCP7940x device
794
795 mcp7941x Select the MCP7941x device
796
797 pcf2127 Select the PCF2127 device
798
799 pcf8523 Select the PCF8523 device
800
801 pcf8563 Select the PCF8563 device
802
803 trickle-diode-type Diode type for trickle charge - "standard" or
804 "schottky" (ABx80x only)
805
806 trickle-resistor-ohms Resistor value for trickle charge (DS1339,
807 ABx80x)
808
809 wakeup-source Specify that the RTC can be used as a wakeup
810 source
811
812 i2c_gpio_sda GPIO used for I2C data (default "23")
813
814 i2c_gpio_scl GPIO used for I2C clock (default "24")
815
816 i2c_gpio_delay_us Clock delay in microseconds
817 (default "2" = ~100kHz)
818
819
820Name: i2c-sensor
821Info: Adds support for a number of I2C barometric pressure and temperature
822 sensors on i2c_arm
823Load: dtoverlay=i2c-sensor,<param>=<val>
824Params: addr Set the address for the BME280, BMP280, TMP102,
825 HDC100X, LM75 or SHT3x
826
827 bme280 Select the Bosch Sensortronic BME280
828 Valid addresses 0x76-0x77, default 0x76
829
830 bmp085 Select the Bosch Sensortronic BMP085
831
832 bmp180 Select the Bosch Sensortronic BMP180
833
834 bmp280 Select the Bosch Sensortronic BMP280
835 Valid addresses 0x76-0x77, default 0x76
836
837 hdc100x Select the Texas Instruments HDC100x temp sensor
838 Valid addresses 0x40-0x43, default 0x40
839
840 htu21 Select the HTU21 temperature and humidity sensor
841
842 lm75 Select the Maxim LM75 temperature sensor
843 Valid addresses 0x48-0x4f, default 0x4f
844
845 lm75addr Deprecated - use addr parameter instead
846
847 si7020 Select the Silicon Labs Si7013/20/21 humidity/
848 temperature sensor
849
850 tmp102 Select the Texas Instruments TMP102 temp sensor
851 Valid addresses 0x48-0x4b, default 0x48
852
853 tsl4531 Select the AMS TSL4531 digital ambient light
854 sensor
855
856 veml6070 Select the Vishay VEML6070 ultraviolet light
857 sensor
858
859 sht3x Select the Sensiron SHT3x temperature and
860 humidity sensor. Valid addresses 0x44-0x45,
861 default 0x44
862
863
864Name: i2c0-bcm2708
865Info: Enable the i2c_bcm2708 driver for the i2c0 bus. Not all pin combinations
866 are usable on all platforms.
867Load: dtoverlay=i2c0-bcm2708,<param>=<val>
868Params: sda0_pin GPIO pin for SDA0 (deprecated - use pins_*)
869 scl0_pin GPIO pin for SCL0 (deprecated - use pins_*)
870 pins_0_1 Use pins 0 and 1 (default)
871 pins_28_29 Use pins 28 and 29
872 pins_44_45 Use pins 44 and 45
873 pins_46_47 Use pins 46 and 47
874
875
876Name: i2c1-bcm2708
877Info: Enable the i2c_bcm2708 driver for the i2c1 bus
878Load: dtoverlay=i2c1-bcm2708,<param>=<val>
879Params: sda1_pin GPIO pin for SDA1 (2 or 44 - default 2)
880 scl1_pin GPIO pin for SCL1 (3 or 45 - default 3)
881 pin_func Alternative pin function (4 (alt0), 6 (alt2) -
882 default 4)
883
884
885Name: i2s-gpio28-31
886Info: move I2S function block to GPIO 28 to 31
887Load: dtoverlay=i2s-gpio28-31
888Params: <None>
889
890
891Name: iqaudio-dac
892Info: Configures the IQaudio DAC audio card
893Load: dtoverlay=iqaudio-dac,<param>
894Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
895 Digital volume control. Enable with
896 "dtoverlay=iqaudio-dac,24db_digital_gain"
897 (The default behaviour is that the Digital
898 volume control is limited to a maximum of
899 0dB. ie. it can attenuate but not provide
900 gain. For most users, this will be desired
901 as it will prevent clipping. By appending
902 the 24db_digital_gain parameter, the Digital
903 volume control will allow up to 24dB of
904 gain. If this parameter is enabled, it is the
905 responsibility of the user to ensure that
906 the Digital volume control is set to a value
907 that does not result in clipping/distortion!)
908
909
910Name: iqaudio-dacplus
911Info: Configures the IQaudio DAC+ audio card
912Load: dtoverlay=iqaudio-dacplus,<param>=<val>
913Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
914 Digital volume control. Enable with
915 "dtoverlay=iqaudio-dacplus,24db_digital_gain"
916 (The default behaviour is that the Digital
917 volume control is limited to a maximum of
918 0dB. ie. it can attenuate but not provide
919 gain. For most users, this will be desired
920 as it will prevent clipping. By appending
921 the 24db_digital_gain parameter, the Digital
922 volume control will allow up to 24dB of
923 gain. If this parameter is enabled, it is the
924 responsibility of the user to ensure that
925 the Digital volume control is set to a value
926 that does not result in clipping/distortion!)
927 auto_mute_amp If specified, unmute/mute the IQaudIO amp when
928 starting/stopping audio playback.
929 unmute_amp If specified, unmute the IQaudIO amp once when
930 the DAC driver module loads.
931
932
933Name: iqaudio-digi-wm8804-audio
934Info: Configures the IQAudIO Digi WM8804 audio card
935Load: dtoverlay=iqaudio-digi-wm8804-audio,<param>=<val>
936Params: card_name Override the default, "IQAudIODigi", card name.
937 dai_name Override the default, "IQAudIO Digi", dai name.
938 dai_stream_name Override the default, "IQAudIO Digi HiFi",
939 dai stream name.
940
941
c1be21dc 942Name: jedec-spi-nor
943Info: Adds support for JEDEC-compliant SPI NOR flash devices. (Note: The
944 "jedec,spi-nor" kernel driver was formerly known as "m25p80".)
945Load: dtoverlay=jedec-spi-nor,<param>=<val>
946Params: flash-spi<n>-<m> Enables flash device on SPI<n>, CS#<m>.
947 flash-fastr-spi<n>-<m> Enables flash device with fast read capability
948 on SPI<n>, CS#<m>.
949
950
2f060b25 951Name: justboom-dac
952Info: Configures the JustBoom DAC HAT, Amp HAT, DAC Zero and Amp Zero audio
953 cards
954Load: dtoverlay=justboom-dac,<param>=<val>
955Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
956 Digital volume control. Enable with
957 "dtoverlay=justboom-dac,24db_digital_gain"
958 (The default behaviour is that the Digital
959 volume control is limited to a maximum of
960 0dB. ie. it can attenuate but not provide
961 gain. For most users, this will be desired
962 as it will prevent clipping. By appending
963 the 24dB_digital_gain parameter, the Digital
964 volume control will allow up to 24dB of
965 gain. If this parameter is enabled, it is the
966 responsibility of the user to ensure that
967 the Digital volume control is set to a value
968 that does not result in clipping/distortion!)
969
970
971Name: justboom-digi
972Info: Configures the JustBoom Digi HAT and Digi Zero audio cards
973Load: dtoverlay=justboom-digi
974Params: <None>
975
976
977Name: lirc-rpi
978Info: Configures lirc-rpi (Linux Infrared Remote Control for Raspberry Pi)
979 Consult the module documentation for more details.
980Load: dtoverlay=lirc-rpi,<param>=<val>
981Params: gpio_out_pin GPIO for output (default "17")
982
983 gpio_in_pin GPIO for input (default "18")
984
985 gpio_in_pull Pull up/down/off on the input pin
986 (default "down")
987
988 sense Override the IR receive auto-detection logic:
989 "0" = force active-high
990 "1" = force active-low
991 "-1" = use auto-detection
992 (default "-1")
993
994 softcarrier Turn the software carrier "on" or "off"
995 (default "on")
996
997 invert "on" = invert the output pin (default "off")
998
999 debug "on" = enable additional debug messages
1000 (default "off")
1001
1002
1003Name: mbed-dac
1004Info: Configures the mbed AudioCODEC (TLV320AIC23B)
1005Load: dtoverlay=mbed-dac
1006Params: <None>
1007
1008
1009Name: mcp23017
1010Info: Configures the MCP23017 I2C GPIO expander
1011Load: dtoverlay=mcp23017,<param>=<val>
1012Params: gpiopin Gpio pin connected to the INTA output of the
1013 MCP23017 (default: 4)
1014
1015 addr I2C address of the MCP23017 (default: 0x20)
1016
1017
1018Name: mcp23s17
1019Info: Configures the MCP23S08/17 SPI GPIO expanders.
1020 If devices are present on SPI1 or SPI2, those interfaces must be enabled
1021 with one of the spi1-1/2/3cs and/or spi2-1/2/3cs overlays.
1022 If interrupts are enabled for a device on a given CS# on a SPI bus, that
1023 device must be the only one present on that SPI bus/CS#.
1024Load: dtoverlay=mcp23s17,<param>=<val>
1025Params: s08-spi<n>-<m>-present 4-bit integer, bitmap indicating MCP23S08
1026 devices present on SPI<n>, CS#<m>
1027
1028 s17-spi<n>-<m>-present 8-bit integer, bitmap indicating MCP23S17
1029 devices present on SPI<n>, CS#<m>
1030
1031 s08-spi<n>-<m>-int-gpio integer, enables interrupts on a single
1032 MCP23S08 device on SPI<n>, CS#<m>, specifies
1033 the GPIO pin to which INT output of MCP23S08
1034 is connected.
1035
1036 s17-spi<n>-<m>-int-gpio integer, enables mirrored interrupts on a
1037 single MCP23S17 device on SPI<n>, CS#<m>,
1038 specifies the GPIO pin to which either INTA
1039 or INTB output of MCP23S17 is connected.
1040
1041
1042Name: mcp2515-can0
1043Info: Configures the MCP2515 CAN controller on spi0.0
1044Load: dtoverlay=mcp2515-can0,<param>=<val>
1045Params: oscillator Clock frequency for the CAN controller (Hz)
1046
1047 spimaxfrequency Maximum SPI frequence (Hz)
1048
1049 interrupt GPIO for interrupt signal
1050
1051
1052Name: mcp2515-can1
1053Info: Configures the MCP2515 CAN controller on spi0.1
1054Load: dtoverlay=mcp2515-can1,<param>=<val>
1055Params: oscillator Clock frequency for the CAN controller (Hz)
1056
1057 spimaxfrequency Maximum SPI frequence (Hz)
1058
1059 interrupt GPIO for interrupt signal
1060
1061
1062Name: mcp3008
1063Info: Configures MCP3008 A/D converters
1064 For devices on spi1 or spi2, the interfaces should be enabled
1065 with one of the spi1-1/2/3cs and/or spi2-1/2/3cs overlays.
1066Load: dtoverlay=mcp3008,<param>[=<val>]
1067Params: spi<n>-<m>-present boolean, configure device at spi<n>, cs<m>
1068 spi<n>-<m>-speed integer, set the spi bus speed for this device
1069
1070
1071Name: mcp3202
1072Info: Configures MCP3202 A/D converters
1073 For devices on spi1 or spi2, the interfaces should be enabled
1074 with one of the spi1-1/2/3cs and/or spi2-1/2/3cs overlays.
1075Load: dtoverlay=mcp3202,<param>[=<val>]
1076Params: spi<n>-<m>-present boolean, configure device at spi<n>, cs<m>
1077 spi<n>-<m>-speed integer, set the spi bus speed for this device
1078
1079
1080Name: media-center
1081Info: Media Center HAT - 2.83" Touch Display + extras by Pi Supply
1082Load: dtoverlay=media-center,<param>=<val>
1083Params: speed Display SPI bus speed
1084 rotate Display rotation {0,90,180,270}
1085 fps Delay between frame updates
1086 xohms Touchpanel sensitivity (X-plate resistance)
1087 swapxy Swap x and y axis
1088 backlight Change backlight GPIO pin {e.g. 12, 18}
1089 gpio_out_pin GPIO for output (default "17")
1090 gpio_in_pin GPIO for input (default "18")
1091 gpio_in_pull Pull up/down/off on the input pin
1092 (default "down")
1093 sense Override the IR receive auto-detection logic:
1094 "0" = force active-high
1095 "1" = force active-low
1096 "-1" = use auto-detection
1097 (default "-1")
1098 softcarrier Turn the software carrier "on" or "off"
1099 (default "on")
1100 invert "on" = invert the output pin (default "off")
1101 debug "on" = enable additional debug messages
1102 (default "off")
1103
1104
1105Name: midi-uart0
1106Info: Configures UART0 (ttyAMA0) so that a requested 38.4kbaud actually gets
1107 31.25kbaud, the frequency required for MIDI
1108Load: dtoverlay=midi-uart0
1109Params: <None>
1110
1111
1112Name: midi-uart1
1113Info: Configures UART1 (ttyS0) so that a requested 38.4kbaud actually gets
1114 31.25kbaud, the frequency required for MIDI
1115Load: dtoverlay=midi-uart1
1116Params: <None>
1117
1118
1119Name: mmc
1120Info: Selects the bcm2835-mmc SD/MMC driver, optionally with overclock
1121Load: dtoverlay=mmc,<param>=<val>
1122Params: overclock_50 Clock (in MHz) to use when the MMC framework
1123 requests 50MHz
1124
1125
1126Name: mpu6050
1127Info: Overlay for i2c connected mpu6050 imu
1128Load: dtoverlay=mpu6050,<param>=<val>
1129Params: interrupt GPIO pin for interrupt (default 4)
1130
1131
1132Name: mz61581
1133Info: MZ61581 display by Tontec
1134Load: dtoverlay=mz61581,<param>=<val>
1135Params: speed Display SPI bus speed
1136
1137 rotate Display rotation {0,90,180,270}
1138
1139 fps Delay between frame updates
1140
1141 txbuflen Transmit buffer length (default 32768)
1142
1143 debug Debug output level {0-7}
1144
1145 xohms Touchpanel sensitivity (X-plate resistance)
1146
1147
1148Name: papirus
1149Info: PaPiRus ePaper Screen by Pi Supply (both HAT and pHAT)
1150Load: dtoverlay=papirus,<param>=<val>
1151Params: panel Display panel (required):
1152 1.44": e1144cs021
1153 2.0": e2200cs021
1154 2.7": e2271cs021
1155
1156 speed Display SPI bus speed
1157
1158
1159[ The pcf2127-rtc overlay has been deleted. See i2c-rtc. ]
1160
1161
1162[ The pcf8523-rtc overlay has been deleted. See i2c-rtc. ]
1163
1164
1165[ The pcf8563-rtc overlay has been deleted. See i2c-rtc. ]
1166
1167
1168Name: pi3-act-led
1169Info: Pi3 uses a GPIO expander to drive the LEDs which can only be accessed
1170 from the VPU. There is a special driver for this with a separate DT
1171 node, which has the unfortunate consequence of breaking the
1172 act_led_gpio and act_led_activelow dtparams.
1173 This overlay changes the GPIO controller back to the standard one and
1174 restores the dtparams.
1175Load: dtoverlay=pi3-act-led,<param>=<val>
1176Params: activelow Set to "on" to invert the sense of the LED
1177 (default "off")
1178
1179 gpio Set which GPIO to use for the activity LED
1180 (in case you want to connect it to an external
1181 device)
1182 REQUIRED
1183
1184
1185Name: pi3-disable-bt
1186Info: Disable Pi3 Bluetooth and restore UART0/ttyAMA0 over GPIOs 14 & 15
1187 N.B. To disable the systemd service that initialises the modem so it
1188 doesn't use the UART, use 'sudo systemctl disable hciuart'.
1189Load: dtoverlay=pi3-disable-bt
1190Params: <None>
1191
1192
1193Name: pi3-disable-wifi
1194Info: Disable Pi3 onboard WiFi
1195Load: dtoverlay=pi3-disable-wifi
1196Params: <None>
1197
1198
1199Name: pi3-miniuart-bt
1200Info: Switch Pi3 Bluetooth function to use the mini-UART (ttyS0) and restore
1201 UART0/ttyAMA0 over GPIOs 14 & 15. Note that this may reduce the maximum
1202 usable baudrate.
1203 N.B. It is also necessary to edit /lib/systemd/system/hciuart.service
1204 and replace ttyAMA0 with ttyS0, unless you have a system with udev rules
1205 that create /dev/serial0 and /dev/serial1, in which case use
1206 /dev/serial1 instead because it will always be correct. Furthermore,
1207 you must also set core_freq=250 in config.txt or the miniuart will not
1208 work.
1209Load: dtoverlay=pi3-miniuart-bt
1210Params: <None>
1211
1212
80d498be
PE		 1213Name: pibell
1214Info: Configures the pibell audio card.
1215Load: dtoverlay=pibell,<param>=<val>
1216Params: alsaname Set the name as it appears in ALSA (default
1217 "PiBell")
1218
1219
2f060b25 1220Name: piscreen
1221Info: PiScreen display by OzzMaker.com
1222Load: dtoverlay=piscreen,<param>=<val>
1223Params: speed Display SPI bus speed
1224
1225 rotate Display rotation {0,90,180,270}
1226
1227 fps Delay between frame updates
1228
1229 debug Debug output level {0-7}
1230
1231 xohms Touchpanel sensitivity (X-plate resistance)
1232
1233
1234Name: piscreen2r
1235Info: PiScreen 2 with resistive TP display by OzzMaker.com
1236Load: dtoverlay=piscreen2r,<param>=<val>
1237Params: speed Display SPI bus speed
1238
1239 rotate Display rotation {0,90,180,270}
1240
1241 fps Delay between frame updates
1242
1243 debug Debug output level {0-7}
1244
1245 xohms Touchpanel sensitivity (X-plate resistance)
1246
1247
1248Name: pisound
1249Info: Configures the Blokas Labs pisound card
1250Load: dtoverlay=pisound
1251Params: <None>
1252
1253
1254Name: pitft22
1255Info: Adafruit PiTFT 2.2" screen
1256Load: dtoverlay=pitft22,<param>=<val>
1257Params: speed Display SPI bus speed
1258
1259 rotate Display rotation {0,90,180,270}
1260
1261 fps Delay between frame updates
1262
1263 debug Debug output level {0-7}
1264
1265
1266Name: pitft28-capacitive
1267Info: Adafruit PiTFT 2.8" capacitive touch screen
1268Load: dtoverlay=pitft28-capacitive,<param>=<val>
1269Params: speed Display SPI bus speed
1270
1271 rotate Display rotation {0,90,180,270}
1272
1273 fps Delay between frame updates
1274
1275 debug Debug output level {0-7}
1276
1277 touch-sizex Touchscreen size x (default 240)
1278
1279 touch-sizey Touchscreen size y (default 320)
1280
1281 touch-invx Touchscreen inverted x axis
1282
1283 touch-invy Touchscreen inverted y axis
1284
1285 touch-swapxy Touchscreen swapped x y axis
1286
1287
1288Name: pitft28-resistive
1289Info: Adafruit PiTFT 2.8" resistive touch screen
1290Load: dtoverlay=pitft28-resistive,<param>=<val>
1291Params: speed Display SPI bus speed
1292
1293 rotate Display rotation {0,90,180,270}
1294
1295 fps Delay between frame updates
1296
1297 debug Debug output level {0-7}
1298
1299
1300Name: pitft35-resistive
1301Info: Adafruit PiTFT 3.5" resistive touch screen
1302Load: dtoverlay=pitft35-resistive,<param>=<val>
1303Params: speed Display SPI bus speed
1304
1305 rotate Display rotation {0,90,180,270}
1306
1307 fps Delay between frame updates
1308
1309 debug Debug output level {0-7}
1310
1311
1312Name: pps-gpio
1313Info: Configures the pps-gpio (pulse-per-second time signal via GPIO).
1314Load: dtoverlay=pps-gpio,<param>=<val>
1315Params: gpiopin Input GPIO (default "18")
1316 assert_falling_edge When present, assert is indicated by a falling
018e4884 1317 edge, rather than by a rising edge (default
1318 off)
1319 capture_clear Generate clear events on the trailing edge
1320 (default off)
2f060b25 1321
1322
1323Name: pwm
1324Info: Configures a single PWM channel
1325 Legal pin,function combinations for each channel:
1326 PWM0: 12,4(Alt0) 18,2(Alt5) 40,4(Alt0) 52,5(Alt1)
1327 PWM1: 13,4(Alt0) 19,2(Alt5) 41,4(Alt0) 45,4(Alt0) 53,5(Alt1)
1328 N.B.:
1329 1) Pin 18 is the only one available on all platforms, and
1330 it is the one used by the I2S audio interface.
1331 Pins 12 and 13 might be better choices on an A+, B+ or Pi2.
1332 2) The onboard analogue audio output uses both PWM channels.
1333 3) So be careful mixing audio and PWM.
1334 4) Currently the clock must have been enabled and configured
1335 by other means.
1336Load: dtoverlay=pwm,<param>=<val>
1337Params: pin Output pin (default 18) - see table
1338 func Pin function (default 2 = Alt5) - see above
1339 clock PWM clock frequency (informational)
1340
1341
1342Name: pwm-2chan
1343Info: Configures both PWM channels
1344 Legal pin,function combinations for each channel:
1345 PWM0: 12,4(Alt0) 18,2(Alt5) 40,4(Alt0) 52,5(Alt1)
1346 PWM1: 13,4(Alt0) 19,2(Alt5) 41,4(Alt0) 45,4(Alt0) 53,5(Alt1)
1347 N.B.:
1348 1) Pin 18 is the only one available on all platforms, and
1349 it is the one used by the I2S audio interface.
1350 Pins 12 and 13 might be better choices on an A+, B+ or Pi2.
1351 2) The onboard analogue audio output uses both PWM channels.
1352 3) So be careful mixing audio and PWM.
1353 4) Currently the clock must have been enabled and configured
1354 by other means.
1355Load: dtoverlay=pwm-2chan,<param>=<val>
1356Params: pin Output pin (default 18) - see table
1357 pin2 Output pin for other channel (default 19)
1358 func Pin function (default 2 = Alt5) - see above
1359 func2 Function for pin2 (default 2 = Alt5)
1360 clock PWM clock frequency (informational)
1361
1362
1363Name: pwm-ir-tx
1364Info: Use GPIO pin as pwm-assisted infrared transmitter output.
1365 This is an alternative to "gpio-ir-tx". pwm-ir-tx makes use
1366 of PWM0 to reduce the CPU load during transmission compared to
1367 gpio-ir-tx which uses bit-banging.
1368 Legal pin,function combinations are:
1369 12,4(Alt0) 18,2(Alt5) 40,4(Alt0) 52,5(Alt1)
1370Load: dtoverlay=pwm-ir-tx,<param>=<val>
1371Params: gpio_pin Output GPIO (default 18)
1372
1373 func Pin function (default 2 = Alt5)
1374
1375
1376Name: qca7000
1377Info: I2SE's Evaluation Board for PLC Stamp micro
1378Load: dtoverlay=qca7000,<param>=<val>
1379Params: int_pin GPIO pin for interrupt signal (default 23)
1380
1381 speed SPI bus speed (default 12 MHz)
1382
1383
2f060b25 1384Name: rotary-encoder
1385Info: Overlay for GPIO connected rotary encoder.
1386Load: dtoverlay=rotary-encoder,<param>=<val>
f69b93f8 1387Params: pin_a GPIO connected to rotary encoder channel A
2f060b25 1388 (default 4).
f69b93f8 1389 pin_b GPIO connected to rotary encoder channel B
2f060b25 1390 (default 17).
1391 relative_axis register a relative axis rather than an
1392 absolute one. Relative axis will only
1393 generate +1/-1 events on the input device,
1394 hence no steps need to be passed.
1395 linux_axis the input subsystem axis to map to this
1396 rotary encoder. Defaults to 0 (ABS_X / REL_X)
1397 rollover Automatic rollover when the rotary value
1398 becomes greater than the specified steps or
1399 smaller than 0. For absolute axis only.
1400 steps-per-period Number of steps (stable states) per period.
1401 The values have the following meaning:
1402 1: Full-period mode (default)
1403 2: Half-period mode
1404 4: Quarter-period mode
1405 steps Number of steps in a full turnaround of the
1406 encoder. Only relevant for absolute axis.
1407 Defaults to 24 which is a typical value for
1408 such devices.
1409 wakeup Boolean, rotary encoder can wake up the
1410 system.
1411 encoding String, the method used to encode steps.
1412 Supported are "gray" (the default and more
1413 common) and "binary".
1414
1415
1416Name: rpi-backlight
1417Info: Raspberry Pi official display backlight driver
1418Load: dtoverlay=rpi-backlight
1419Params: <None>
1420
1421
1422Name: rpi-cirrus-wm5102
1423Info: Configures the Cirrus Logic Audio Card
1424Load: dtoverlay=rpi-cirrus-wm5102
1425Params: <None>
1426
1427
1428Name: rpi-dac
1429Info: Configures the RPi DAC audio card
1430Load: dtoverlay=rpi-dac
1431Params: <None>
1432
1433
1434Name: rpi-display
1435Info: RPi-Display - 2.8" Touch Display by Watterott
1436Load: dtoverlay=rpi-display,<param>=<val>
1437Params: speed Display SPI bus speed
1438 rotate Display rotation {0,90,180,270}
1439 fps Delay between frame updates
1440 debug Debug output level {0-7}
1441 xohms Touchpanel sensitivity (X-plate resistance)
1442 swapxy Swap x and y axis
1443 backlight Change backlight GPIO pin {e.g. 12, 18}
1444
1445
1446Name: rpi-ft5406
1447Info: Official Raspberry Pi display touchscreen
1448Load: dtoverlay=rpi-ft5406,<param>=<val>
1449Params: touchscreen-size-x Touchscreen X resolution (default 800)
1450 touchscreen-size-y Touchscreen Y resolution (default 600);
1451 touchscreen-inverted-x Invert touchscreen X coordinates (default 0);
1452 touchscreen-inverted-y Invert touchscreen Y coordinates (default 0);
1453 touchscreen-swapped-x-y Swap X and Y cordinates (default 0);
1454
1455
1456Name: rpi-proto
1457Info: Configures the RPi Proto audio card
1458Load: dtoverlay=rpi-proto
1459Params: <None>
1460
1461
1462Name: rpi-sense
1463Info: Raspberry Pi Sense HAT
1464Load: dtoverlay=rpi-sense
1465Params: <None>
1466
1467
1468Name: rpi-tv
1469Info: Raspberry Pi TV HAT
1470Load: dtoverlay=rpi-tv
1471Params: <None>
1472
1473
1474Name: rra-digidac1-wm8741-audio
1475Info: Configures the Red Rocks Audio DigiDAC1 soundcard
1476Load: dtoverlay=rra-digidac1-wm8741-audio
1477Params: <None>
1478
1479
1480Name: sc16is750-i2c
1481Info: Overlay for the NXP SC16IS750 UART with I2C Interface
ceed6911
PE		 1482 Enables the chip on I2C1 at 0x48 (or the "addr" parameter value). To
1483 select another address, please refer to table 10 in reference manual.
2f060b25 1484Load: dtoverlay=sc16is750-i2c,<param>=<val>
1485Params: int_pin GPIO used for IRQ (default 24)
1486 addr Address (default 0x48)
1487
1488
ceed6911
PE		 1489Name: sc16is752-i2c
1490Info: Overlay for the NXP SC16IS752 dual UART with I2C Interface
1491 Enables the chip on I2C1 at 0x48 (or the "addr" parameter value). To
1492 select another address, please refer to table 10 in reference manual.
1493Load: dtoverlay=sc16is752-i2c,<param>=<val>
1494Params: int_pin GPIO used for IRQ (default 24)
1495 addr Address (default 0x48)
1496 xtal On-board crystal frequency (default 14745600)
1497
1498
2f060b25 1499Name: sc16is752-spi1
1500Info: Overlay for the NXP SC16IS752 Dual UART with SPI Interface
1501 Enables the chip on SPI1.
1502 N.B.: spi1 is only accessible on devices with a 40pin header, eg:
1503 A+, B+, Zero and PI2 B; as well as the Compute Module.
1504
1505Load: dtoverlay=sc16is752-spi1,<param>=<val>
1506Params: int_pin GPIO used for IRQ (default 24)
1507
1508
1509Name: sdhost
1510Info: Selects the bcm2835-sdhost SD/MMC driver, optionally with overclock.
1511 N.B. This overlay is designed for situations where the mmc driver is
1512 the default, so it disables the other (mmc) interface - this will kill
1513 WiFi on a Pi3. If this isn't what you want, either use the sdtweak
1514 overlay or the new sd_* dtparams of the base DTBs.
1515Load: dtoverlay=sdhost,<param>=<val>
1516Params: overclock_50 Clock (in MHz) to use when the MMC framework
1517 requests 50MHz
1518
1519 force_pio Disable DMA support (default off)
1520
1521 pio_limit Number of blocks above which to use DMA
1522 (default 1)
1523
1524 debug Enable debug output (default off)
1525
1526
1527Name: sdio
1528Info: Selects the bcm2835-sdhost SD/MMC driver, optionally with overclock,
1529 and enables SDIO via GPIOs 22-27.
1530Load: dtoverlay=sdio,<param>=<val>
1531Params: sdio_overclock SDIO Clock (in MHz) to use when the MMC
1532 framework requests 50MHz
1533
1534 poll_once Disable SDIO-device polling every second
1535 (default on: polling once at boot-time)
1536
1537 bus_width Set the SDIO host bus width (default 4 bits)
1538
1539
1540Name: sdio-1bit
1541Info: Selects the bcm2835-sdhost SD/MMC driver, optionally with overclock,
1542 and enables 1-bit SDIO via GPIOs 22-25.
1543Load: dtoverlay=sdio-1bit,<param>=<val>
1544Params: sdio_overclock SDIO Clock (in MHz) to use when the MMC
1545 framework requests 50MHz
1546
1547 poll_once Disable SDIO-device polling every second
1548 (default on: polling once at boot-time)
1549
1550
1551Name: sdtweak
1552Info: Tunes the bcm2835-sdhost SD/MMC driver
1553 N.B. This functionality is now available via the sd_* dtparams in the
1554 base DTB.
1555Load: dtoverlay=sdtweak,<param>=<val>
1556Params: overclock_50 Clock (in MHz) to use when the MMC framework
1557 requests 50MHz
1558
1559 force_pio Disable DMA support (default off)
1560
1561 pio_limit Number of blocks above which to use DMA
1562 (default 1)
1563
1564 debug Enable debug output (default off)
1565
1566
1567Name: smi
1568Info: Enables the Secondary Memory Interface peripheral. Uses GPIOs 2-25!
1569Load: dtoverlay=smi
1570Params: <None>
1571
1572
1573Name: smi-dev
1574Info: Enables the userspace interface for the SMI driver
1575Load: dtoverlay=smi-dev
1576Params: <None>
1577
1578
1579Name: smi-nand
1580Info: Enables access to NAND flash via the SMI interface
1581Load: dtoverlay=smi-nand
1582Params: <None>
1583
1584
1585Name: spi-gpio35-39
1586Info: Move SPI function block to GPIO 35 to 39
1587Load: dtoverlay=spi-gpio35-39
1588Params: <None>
1589
1590
1591Name: spi-rtc
1592Info: Adds support for a number of SPI Real Time Clock devices
1593Load: dtoverlay=spi-rtc,<param>=<val>
1594Params: pcf2123 Select the PCF2123 device
1595
1596
1597Name: spi0-cs
1598Info: Allows the (software) CS pins for SPI0 to be changed
1599Load: dtoverlay=spi0-cs,<param>=<val>
1600Params: cs0_pin GPIO pin for CS0 (default 8)
1601 cs1_pin GPIO pin for CS1 (default 7)
1602
1603
1604Name: spi0-hw-cs
1605Info: Re-enables hardware CS/CE (chip selects) for SPI0
1606Load: dtoverlay=spi0-hw-cs
1607Params: <None>
1608
1609
1610Name: spi1-1cs
1611Info: Enables spi1 with a single chip select (CS) line and associated spidev
1612 dev node. The gpio pin number for the CS line and spidev device node
1613 creation are configurable.
1614 N.B.: spi1 is only accessible on devices with a 40pin header, eg:
1615 A+, B+, Zero and PI2 B; as well as the Compute Module.
1616Load: dtoverlay=spi1-1cs,<param>=<val>
1617Params: cs0_pin GPIO pin for CS0 (default 18 - BCM SPI1_CE0).
1618 cs0_spidev Set to 'disabled' to stop the creation of a
1619 userspace device node /dev/spidev1.0 (default
1620 is 'okay' or enabled).
1621
1622
1623Name: spi1-2cs
1624Info: Enables spi1 with two chip select (CS) lines and associated spidev
1625 dev nodes. The gpio pin numbers for the CS lines and spidev device node
1626 creation are configurable.
1627 N.B.: spi1 is only accessible on devices with a 40pin header, eg:
1628 A+, B+, Zero and PI2 B; as well as the Compute Module.
1629Load: dtoverlay=spi1-2cs,<param>=<val>
1630Params: cs0_pin GPIO pin for CS0 (default 18 - BCM SPI1_CE0).
1631 cs1_pin GPIO pin for CS1 (default 17 - BCM SPI1_CE1).
1632 cs0_spidev Set to 'disabled' to stop the creation of a
1633 userspace device node /dev/spidev1.0 (default
1634 is 'okay' or enabled).
1635 cs1_spidev Set to 'disabled' to stop the creation of a
1636 userspace device node /dev/spidev1.1 (default
1637 is 'okay' or enabled).
1638
1639
1640Name: spi1-3cs
1641Info: Enables spi1 with three chip select (CS) lines and associated spidev
1642 dev nodes. The gpio pin numbers for the CS lines and spidev device node
1643 creation are configurable.
1644 N.B.: spi1 is only accessible on devices with a 40pin header, eg:
1645 A+, B+, Zero and PI2 B; as well as the Compute Module.
1646Load: dtoverlay=spi1-3cs,<param>=<val>
1647Params: cs0_pin GPIO pin for CS0 (default 18 - BCM SPI1_CE0).
1648 cs1_pin GPIO pin for CS1 (default 17 - BCM SPI1_CE1).
1649 cs2_pin GPIO pin for CS2 (default 16 - BCM SPI1_CE2).
1650 cs0_spidev Set to 'disabled' to stop the creation of a
1651 userspace device node /dev/spidev1.0 (default
1652 is 'okay' or enabled).
1653 cs1_spidev Set to 'disabled' to stop the creation of a
1654 userspace device node /dev/spidev1.1 (default
1655 is 'okay' or enabled).
1656 cs2_spidev Set to 'disabled' to stop the creation of a
1657 userspace device node /dev/spidev1.2 (default
1658 is 'okay' or enabled).
1659
1660
1661Name: spi2-1cs
1662Info: Enables spi2 with a single chip select (CS) line and associated spidev
1663 dev node. The gpio pin number for the CS line and spidev device node
1664 creation are configurable.
1665 N.B.: spi2 is only accessible with the Compute Module.
1666Load: dtoverlay=spi2-1cs,<param>=<val>
1667Params: cs0_pin GPIO pin for CS0 (default 43 - BCM SPI2_CE0).
1668 cs0_spidev Set to 'disabled' to stop the creation of a
1669 userspace device node /dev/spidev2.0 (default
1670 is 'okay' or enabled).
1671
1672
1673Name: spi2-2cs
1674Info: Enables spi2 with two chip select (CS) lines and associated spidev
1675 dev nodes. The gpio pin numbers for the CS lines and spidev device node
1676 creation are configurable.
1677 N.B.: spi2 is only accessible with the Compute Module.
1678Load: dtoverlay=spi2-2cs,<param>=<val>
1679Params: cs0_pin GPIO pin for CS0 (default 43 - BCM SPI2_CE0).
1680 cs1_pin GPIO pin for CS1 (default 44 - BCM SPI2_CE1).
1681 cs0_spidev Set to 'disabled' to stop the creation of a
1682 userspace device node /dev/spidev2.0 (default
1683 is 'okay' or enabled).
1684 cs1_spidev Set to 'disabled' to stop the creation of a
1685 userspace device node /dev/spidev2.1 (default
1686 is 'okay' or enabled).
1687
1688
1689Name: spi2-3cs
1690Info: Enables spi2 with three chip select (CS) lines and associated spidev
1691 dev nodes. The gpio pin numbers for the CS lines and spidev device node
1692 creation are configurable.
1693 N.B.: spi2 is only accessible with the Compute Module.
1694Load: dtoverlay=spi2-3cs,<param>=<val>
1695Params: cs0_pin GPIO pin for CS0 (default 43 - BCM SPI2_CE0).
1696 cs1_pin GPIO pin for CS1 (default 44 - BCM SPI2_CE1).
1697 cs2_pin GPIO pin for CS2 (default 45 - BCM SPI2_CE2).
1698 cs0_spidev Set to 'disabled' to stop the creation of a
1699 userspace device node /dev/spidev2.0 (default
1700 is 'okay' or enabled).
1701 cs1_spidev Set to 'disabled' to stop the creation of a
1702 userspace device node /dev/spidev2.1 (default
1703 is 'okay' or enabled).
1704 cs2_spidev Set to 'disabled' to stop the creation of a
1705 userspace device node /dev/spidev2.2 (default
1706 is 'okay' or enabled).
1707
1708
31428615
RWH		 1709Name: superaudioboard
1710Info: Configures the SuperAudioBoard sound card
1711Load: dtoverlay=superaudioboard,<param>=<val>
1712Params: gpiopin GPIO pin for codec reset
1713
1714
b5cf7f57 1715Name: sx150x
1716Info: Configures the Semtech SX150X I2C GPIO expanders.
1717Load: dtoverlay=sx150x,<param>=<val>
1718Params: sx150<x>-<n>-<m> Enables SX150X device on I2C#<n> with slave
1719 address <m>. <x> may be 1-9. <n> may be 0 or 1.
1720 Permissible values of <m> (which is denoted in
1721 hex) depend on the device variant. For SX1501,
1722 SX1502, SX1504 and SX1505, <m> may be 20 or 21.
1723 For SX1503 and SX1506, <m> may be 20. For
1724 SX1507 and SX1509, <m> may be 3E, 3F, 70 or 71.
1725 For SX1508, <m> may be 20, 21, 22 or 23.
1726
1727 sx150<x>-<n>-<m>-int-gpio
1728 Integer, enables interrupts on SX150X device on
1729 I2C#<n> with slave address <m>, specifies
1730 the GPIO pin to which NINT output of SX150X is
1731 connected.
1732
1733
2f060b25 1734Name: tinylcd35
1735Info: 3.5" Color TFT Display by www.tinylcd.com
1736 Options: Touch, RTC, keypad
1737Load: dtoverlay=tinylcd35,<param>=<val>
1738Params: speed Display SPI bus speed
1739
1740 rotate Display rotation {0,90,180,270}
1741
1742 fps Delay between frame updates
1743
1744 debug Debug output level {0-7}
1745
1746 touch Enable touch panel
1747
1748 touchgpio Touch controller IRQ GPIO
1749
1750 xohms Touchpanel: Resistance of X-plate in ohms
1751
1752 rtc-pcf PCF8563 Real Time Clock
1753
1754 rtc-ds DS1307 Real Time Clock
1755
1756 keypad Enable keypad
1757
1758 Examples:
1759 Display with touchpanel, PCF8563 RTC and keypad:
1760 dtoverlay=tinylcd35,touch,rtc-pcf,keypad
1761 Old touch display:
1762 dtoverlay=tinylcd35,touch,touchgpio=3
1763
1764
1765Name: uart0
1766Info: Change the pin usage of uart0
1767Load: dtoverlay=uart0,<param>=<val>
1768Params: txd0_pin GPIO pin for TXD0 (14, 32 or 36 - default 14)
1769
1770 rxd0_pin GPIO pin for RXD0 (15, 33 or 37 - default 15)
1771
1772 pin_func Alternative pin function - 4(Alt0) for 14&15,
1773 7(Alt3) for 32&33, 6(Alt2) for 36&37
1774
1775
1776Name: uart1
1777Info: Change the pin usage of uart1
1778Load: dtoverlay=uart1,<param>=<val>
1779Params: txd1_pin GPIO pin for TXD1 (14, 32 or 40 - default 14)
1780
1781 rxd1_pin GPIO pin for RXD1 (15, 33 or 41 - default 15)
1782
1783
3412e380
PE		 1784Name: upstream
1785Info: Allow usage of downstream .dtb with upstream kernel. Comprises
1786 vc4-kms-v3d, dwc2 and upstream-aux-interrupt overlays.
1787Load: dtoverlay=upstream
1788Params: <None>
1789
1790
77f6e6c1
AG		 1791Name: upstream-aux-interrupt
1792Info: Allow usage of downstream .dtb with upstream kernel by binding AUX
3412e380
PE		 1793 devices directly to the shared AUX interrupt line. One of the parts
1794 of the 'upstream' overlay
77f6e6c1
AG		 1795Load: dtoverlay=upstream-aux-interrupt
1796Params: <None>
1797
1798
2f060b25 1799Name: vc4-fkms-v3d
1800Info: Enable Eric Anholt's DRM VC4 V3D driver on top of the dispmanx
1801 display stack.
1802Load: dtoverlay=vc4-fkms-v3d,<param>
1803Params: cma-256 CMA is 256MB, 256MB-aligned (needs 1GB)
1804 cma-192 CMA is 192MB, 256MB-aligned (needs 1GB)
1805 cma-128 CMA is 128MB, 128MB-aligned
1806 cma-96 CMA is 96MB, 128MB-aligned
1807 cma-64 CMA is 64MB, 64MB-aligned
1808
1809
1810Name: vc4-kms-v3d
1811Info: Enable Eric Anholt's DRM VC4 HDMI/HVS/V3D driver. Running startx or
1812 booting to GUI while this overlay is in use will cause interesting
1813 lockups.
1814Load: dtoverlay=vc4-kms-v3d,<param>
1815Params: cma-256 CMA is 256MB, 256MB-aligned (needs 1GB)
1816 cma-192 CMA is 192MB, 256MB-aligned (needs 1GB)
1817 cma-128 CMA is 128MB, 128MB-aligned
1818 cma-96 CMA is 96MB, 128MB-aligned
1819 cma-64 CMA is 64MB, 64MB-aligned
1820
1821
1822Name: vga666
1823Info: Overlay for the Fen Logic VGA666 board
1824 This uses GPIOs 2-21 (so no I2C), and activates the output 2-3 seconds
1825 after the kernel has started.
1826Load: dtoverlay=vga666
1827Params: <None>
1828
1829
1830Name: w1-gpio
1831Info: Configures the w1-gpio Onewire interface module.
1832 Use this overlay if you *don't* need a GPIO to drive an external pullup.
1833Load: dtoverlay=w1-gpio,<param>=<val>
1834Params: gpiopin GPIO for I/O (default "4")
1835
1836 pullup Non-zero, "on", or "y" to enable the parasitic
1837 power (2-wire, power-on-data) feature
1838
1839
1840Name: w1-gpio-pullup
1841Info: Configures the w1-gpio Onewire interface module.
1842 Use this overlay if you *do* need a GPIO to drive an external pullup.
1843Load: dtoverlay=w1-gpio-pullup,<param>=<val>
1844Params: gpiopin GPIO for I/O (default "4")
1845
1846 pullup Non-zero, "on", or "y" to enable the parasitic
1847 power (2-wire, power-on-data) feature
1848
1849 extpullup GPIO for external pullup (default "5")
1850
1851
1852Name: wittypi
1853Info: Configures the wittypi RTC module.
1854Load: dtoverlay=wittypi,<param>=<val>
1855Params: led_gpio GPIO for LED (default "17")
1856 led_trigger Choose which activity the LED tracks (default
1857 "default-on")
1858
1859
1860Troubleshooting
1861===============
1862
1863If you are experiencing problems that you think are DT-related, enable DT
1864diagnostic output by adding this to /boot/config.txt:
1865
1866 dtdebug=on
1867
1868and rebooting. Then run:
1869
1870 sudo vcdbg log msg
1871
1872and look for relevant messages.
1873
1874Further reading
1875===============
1876
1877This is only meant to be a quick introduction to the subject of Device Tree on
1878Raspberry Pi. There is a more complete explanation here:
1879
1880http://www.raspberrypi.org/documentation/configuration/device-tree.md
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