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Add support for Silicon Labs Si7013/20/21 humidity/temperature sensor.
[mirror_ubuntu-zesty-kernel.git] / arch / arm / boot / dts / overlays / README
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e7ecc4b5 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
36raspi-config
37============
38
39The Advanced Options section of the raspi-config utility can enable and disable
40Device Tree use, as well as toggling the I2C and SPI interfaces. Note that it
41is possible to both enable an interface and blacklist the driver, if for some
42reason you should want to defer the loading.
43
44Modules
45=======
46
47As well as describing the hardware, Device Tree also gives enough information
48to allow suitable driver modules to be located and loaded, with the corollary
49that unneeded modules are not loaded. As a result it should be possible to
50remove lines from /etc/modules, and /etc/modprobe.d/raspi-blacklist.conf can
51have its contents deleted (or commented out).
52
53Using Overlays
54==============
55
56Overlays are loaded using the "dtoverlay" directive. As an example, consider
57the popular lirc-rpi module, the Linux Infrared Remote Control driver. In the
58pre-DT world this would be loaded from /etc/modules, with an explicit
59"modprobe lirc-rpi" command, or programmatically by lircd. With DT enabled,
60this becomes a line in config.txt:
61
62 dtoverlay=lirc-rpi
63
64This causes the file /boot/overlays/lirc-rpi.dtbo to be loaded. By
65default it will use GPIOs 17 (out) and 18 (in), but this can be modified using
66DT parameters:
67
68 dtoverlay=lirc-rpi,gpio_out_pin=17,gpio_in_pin=13
69
70Parameters always have default values, although in some cases (e.g. "w1-gpio")
71it is necessary to provided multiple overlays in order to get the desired
72behaviour. See the list of overlays below for a description of the parameters
73and their defaults.
74
75The Overlay and Parameter Reference
76===================================
77
78N.B. When editing this file, please preserve the indentation levels to make it
79simple to parse programmatically. NO HARD TABS.
80
81
82Name: <The base DTB>
83Info: Configures the base Raspberry Pi hardware
84Load: <loaded automatically>
85Params:
86 audio Set to "on" to enable the onboard ALSA audio
87 interface (default "off")
88
89 i2c_arm Set to "on" to enable the ARM's i2c interface
90 (default "off")
91
92 i2c_vc Set to "on" to enable the i2c interface
93 usually reserved for the VideoCore processor
94 (default "off")
95
96 i2c An alias for i2c_arm
97
98 i2c_arm_baudrate Set the baudrate of the ARM's i2c interface
99 (default "100000")
100
101 i2c_vc_baudrate Set the baudrate of the VideoCore i2c interface
102 (default "100000")
103
104 i2c_baudrate An alias for i2c_arm_baudrate
105
106 i2s Set to "on" to enable the i2s interface
107 (default "off")
108
109 spi Set to "on" to enable the spi interfaces
110 (default "off")
111
112 random Set to "on" to enable the hardware random
113 number generator (default "on")
114
115 sd_overclock Clock (in MHz) to use when the MMC framework
116 requests 50MHz
117
118 sd_force_pio Disable DMA support for SD driver (default off)
119
120 sd_pio_limit Number of blocks above which to use DMA for
121 SD card (default 1)
122
123 sd_debug Enable debug output from SD driver (default off)
124
125 uart0 Set to "off" to disable uart0 (default "on")
126
127 uart1 Set to "on" or "off" to enable or disable uart1
128 (default varies)
129
130 watchdog Set to "on" to enable the hardware watchdog
131 (default "off")
132
133 act_led_trigger Choose which activity the LED tracks.
134 Use "heartbeat" for a nice load indicator.
135 (default "mmc")
136
137 act_led_activelow Set to "on" to invert the sense of the LED
138 (default "off")
139 N.B. For Pi3 see pi3-act-led overlay.
140
141 act_led_gpio Set which GPIO to use for the activity LED
142 (in case you want to connect it to an external
143 device)
144 (default "16" on a non-Plus board, "47" on a
145 Plus or Pi 2)
146 N.B. For Pi3 see pi3-act-led overlay.
147
148 pwr_led_trigger
149 pwr_led_activelow
150 pwr_led_gpio
151 As for act_led_*, but using the PWR LED.
152 Not available on Model A/B boards.
153
154 N.B. It is recommended to only enable those interfaces that are needed.
155 Leaving all interfaces enabled can lead to unwanted behaviour (i2c_vc
156 interfering with Pi Camera, I2S and SPI hogging GPIO pins, etc.)
157 Note also that i2c, i2c_arm and i2c_vc are aliases for the physical
158 interfaces i2c0 and i2c1. Use of the numeric variants is still possible
159 but deprecated because the ARM/VC assignments differ between board
160 revisions. The same board-specific mapping applies to i2c_baudrate,
161 and the other i2c baudrate parameters.
162
163
164Name: adau1977-adc
165Info: Overlay for activation of ADAU1977 ADC codec over I2C for control
166 and I2S for data.
167Load: dtoverlay=adau1977-adc
168Params: <None>
169
170
171Name: ads1015
172Info: Overlay for activation of Texas Instruments ADS1015 ADC over I2C
173Load: dtoverlay=ads1015,<param>=<val>
174Params: addr I2C bus address of device. Set based on how the
175 addr pin is wired. (default=0x48 assumes addr
176 is pulled to GND)
177 cha_enable Enable virtual channel a. (default=true)
178 cha_cfg Set the configuration for virtual channel a.
179 (default=4 configures this channel for the
180 voltage at A0 with respect to GND)
181 cha_datarate Set the datarate (samples/sec) for this channel.
182 (default=4 sets 1600 sps)
183 cha_gain Set the gain of the Programmable Gain
184 Amplifier for this channel. (default=2 sets the
185 full scale of the channel to 2.048 Volts)
186
187 Channel (ch) parameters can be set for each enabled channel.
188 A maximum of 4 channels can be enabled (letters a thru d).
189 For more information refer to the device datasheet at:
190 http://www.ti.com/lit/ds/symlink/ads1015.pdf
191
192
193Name: ads7846
194Info: ADS7846 Touch controller
195Load: dtoverlay=ads7846,<param>=<val>
196Params: cs SPI bus Chip Select (default 1)
197 speed SPI bus speed (default 2MHz, max 3.25MHz)
198 penirq GPIO used for PENIRQ. REQUIRED
199 penirq_pull Set GPIO pull (default 0=none, 2=pullup)
200 swapxy Swap x and y axis
201 xmin Minimum value on the X axis (default 0)
202 ymin Minimum value on the Y axis (default 0)
203 xmax Maximum value on the X axis (default 4095)
204 ymax Maximum value on the Y axis (default 4095)
205 pmin Minimum reported pressure value (default 0)
206 pmax Maximum reported pressure value (default 65535)
207 xohms Touchpanel sensitivity (X-plate resistance)
208 (default 400)
209
210 penirq is required and usually xohms (60-100) has to be set as well.
211 Apart from that, pmax (255) and swapxy are also common.
212 The rest of the calibration can be done with xinput-calibrator.
213 See: github.com/notro/fbtft/wiki/FBTFT-on-Raspian
214 Device Tree binding document:
215 www.kernel.org/doc/Documentation/devicetree/bindings/input/ads7846.txt
216
217
218Name: akkordion-iqdacplus
219Info: Configures the Digital Dreamtime Akkordion Music Player (based on the
220 OEM IQAudIO DAC+ or DAC Zero module).
221Load: dtoverlay=akkordion-iqdacplus,<param>=<val>
222Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
223 Digital volume control. Enable with
224 dtoverlay=akkordion-iqdacplus,24db_digital_gain
225 (The default behaviour is that the Digital
226 volume control is limited to a maximum of
227 0dB. ie. it can attenuate but not provide
228 gain. For most users, this will be desired
229 as it will prevent clipping. By appending
230 the 24db_digital_gain parameter, the Digital
231 volume control will allow up to 24dB of
232 gain. If this parameter is enabled, it is the
233 responsibility of the user to ensure that
234 the Digital volume control is set to a value
235 that does not result in clipping/distortion!)
236
237
238Name: allo-piano-dac-pcm512x-audio
239Info: Configures the Allo Piano DAC (2.0/2.1) audio cards.
240 (NB. This initial support is for 2.0 channel audio ONLY! ie. stereo.
241 The subwoofer outputs on the Piano 2.1 are not currently supported!)
242Load: dtoverlay=allo-piano-dac-pcm512x-audio,<param>
243Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
244 Digital volume control.
245 (The default behaviour is that the Digital
246 volume control is limited to a maximum of
247 0dB. ie. it can attenuate but not provide
248 gain. For most users, this will be desired
249 as it will prevent clipping. By appending
250 the 24db_digital_gain parameter, the Digital
251 volume control will allow up to 24dB of
252 gain. If this parameter is enabled, it is the
253 responsibility of the user to ensure that
254 the Digital volume control is set to a value
255 that does not result in clipping/distortion!)
256
257
258Name: at86rf233
259Info: Configures the Atmel AT86RF233 802.15.4 low-power WPAN transceiver,
260 connected to spi0.0
261Load: dtoverlay=at86rf233,<param>=<val>
262Params: interrupt GPIO used for INT (default 23)
263 reset GPIO used for Reset (default 24)
264 sleep GPIO used for Sleep (default 25)
265 speed SPI bus speed in Hz (default 3000000)
266 trim Fine tuning of the internal capacitance
267 arrays (0=+0pF, 15=+4.5pF, default 15)
268
269
270Name: audioinjector-wm8731-audio
271Info: Configures the audioinjector.net audio add on soundcard
272Load: dtoverlay=audioinjector-wm8731-audio
273Params: <None>
274
275
276Name: audremap
277Info: Switches PWM sound output to pins 12 (Right) & 13 (Left)
278Load: dtoverlay=audremap,<param>=<val>
279Params: swap_lr Reverse the channel allocation, which will also
280 swap the audio jack outputs (default off)
281 enable_jack Don't switch off the audio jack output
282 (default off)
283
284
285Name: bmp085_i2c-sensor
286Info: This overlay is now deprecated - see i2c-sensor
287Load: dtoverlay=bmp085_i2c-sensor
288Params: <None>
289
290
291Name: dht11
292Info: Overlay for the DHT11/DHT21/DHT22 humidity/temperature sensors
293 Also sometimes found with the part number(s) AM230x.
294Load: dtoverlay=dht11,<param>=<val>
295Params: gpiopin GPIO connected to the sensor's DATA output.
296 (default 4)
297
298
299Name: dionaudio-loco
300Info: Configures the Dion Audio LOCO DAC-AMP
301Load: dtoverlay=dionaudio-loco
302Params: <None>
303
304
305Name: dpi18
306Info: Overlay for a generic 18-bit DPI display
307 This uses GPIOs 0-21 (so no I2C, uart etc.), and activates the output
308 2-3 seconds after the kernel has started.
309Load: dtoverlay=dpi18
310Params: <None>
311
312
313Name: dpi24
314Info: Overlay for a generic 24-bit DPI display
315 This uses GPIOs 0-27 (so no I2C, uart etc.), and activates the output
316 2-3 seconds after the kernel has started.
317Load: dtoverlay=dpi24
318Params: <None>
319
320
321Name: dwc-otg
322Info: Selects the dwc_otg USB controller driver which has fiq support. This
323 is the default on all except the Pi Zero which defaults to dwc2.
324Load: dtoverlay=dwc-otg
325Params: <None>
326
327
328Name: dwc2
329Info: Selects the dwc2 USB controller driver
330Load: dtoverlay=dwc2,<param>=<val>
331Params: dr_mode Dual role mode: "host", "peripheral" or "otg"
332
333 g-rx-fifo-size Size of rx fifo size in gadget mode
334
335 g-np-tx-fifo-size Size of non-periodic tx fifo size in gadget
336 mode
337
338 g-tx-fifo-size Size of periodic tx fifo per endpoint
339 (except ep0) in gadget mode
340
341
342[ The ds1307-rtc overlay has been deleted. See i2c-rtc. ]
343
344
345Name: enc28j60
346Info: Overlay for the Microchip ENC28J60 Ethernet Controller on SPI0
347Load: dtoverlay=enc28j60,<param>=<val>
348Params: int_pin GPIO used for INT (default 25)
349
350 speed SPI bus speed (default 12000000)
351
352
353Name: enc28j60-spi2
354Info: Overlay for the Microchip ENC28J60 Ethernet Controller on SPI2
355Load: dtoverlay=enc28j60-spi2,<param>=<val>
356Params: int_pin GPIO used for INT (default 39)
357
358 speed SPI bus speed (default 12000000)
359
360
361Name: gpio-ir
362Info: Use GPIO pin as rc-core style infrared receiver input. The rc-core-
363 based gpio_ir_recv driver maps received keys directly to a
364 /dev/input/event* device, all decoding is done by the kernel - LIRC is
365 not required! The key mapping and other decoding parameters can be
366 configured by "ir-keytable" tool.
367Load: dtoverlay=gpio-ir,<param>=<val>
368Params: gpio_pin Input pin number. Default is 18.
369
370 gpio_pull Desired pull-up/down state (off, down, up)
371 Default is "down".
372
373 rc-map-name Default rc keymap (can also be changed by
374 ir-keytable), defaults to "rc-rc6-mce"
375
376
377Name: gpio-poweroff
378Info: Drives a GPIO high or low on poweroff (including halt)
379Load: dtoverlay=gpio-poweroff,<param>=<val>
380Params: gpiopin GPIO for signalling (default 26)
381
382 active_low Set if the power control device requires a
383 high->low transition to trigger a power-down.
384 Note that this will require the support of a
385 custom dt-blob.bin to prevent a power-down
386 during the boot process, and that a reboot
387 will also cause the pin to go low.
388
389
390Name: hifiberry-amp
391Info: Configures the HifiBerry Amp and Amp+ audio cards
392Load: dtoverlay=hifiberry-amp
393Params: <None>
394
395
396Name: hifiberry-dac
397Info: Configures the HifiBerry DAC audio card
398Load: dtoverlay=hifiberry-dac
399Params: <None>
400
401
402Name: hifiberry-dacplus
403Info: Configures the HifiBerry DAC+ audio card
404Load: dtoverlay=hifiberry-dacplus,<param>=<val>
405Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
406 Digital volume control. Enable with
407 "dtoverlay=hifiberry-dacplus,24db_digital_gain"
408 (The default behaviour is that the Digital
409 volume control is limited to a maximum of
410 0dB. ie. it can attenuate but not provide
411 gain. For most users, this will be desired
412 as it will prevent clipping. By appending
413 the 24dB_digital_gain parameter, the Digital
414 volume control will allow up to 24dB of
415 gain. If this parameter is enabled, it is the
416 responsibility of the user to ensure that
417 the Digital volume control is set to a value
418 that does not result in clipping/distortion!)
419 slave Force DAC+ Pro into slave mode, using Pi as
420 master for bit clock and frame clock.
421
422
423Name: hifiberry-digi
424Info: Configures the HifiBerry Digi and Digi+ audio card
425Load: dtoverlay=hifiberry-digi
426Params: <None>
427
428
429Name: hifiberry-digi-pro
430Info: Configures the HifiBerry Digi+ Pro audio card
431Load: dtoverlay=hifiberry-digi-pro
432Params: <None>
433
434
435Name: hy28a
436Info: HY28A - 2.8" TFT LCD Display Module by HAOYU Electronics
437 Default values match Texy's display shield
438Load: dtoverlay=hy28a,<param>=<val>
439Params: speed Display SPI bus speed
440
441 rotate Display rotation {0,90,180,270}
442
443 fps Delay between frame updates
444
445 debug Debug output level {0-7}
446
447 xohms Touchpanel sensitivity (X-plate resistance)
448
449 resetgpio GPIO used to reset controller
450
451 ledgpio GPIO used to control backlight
452
453
454Name: hy28b
455Info: HY28B - 2.8" TFT LCD Display Module by HAOYU Electronics
456 Default values match Texy's display shield
457Load: dtoverlay=hy28b,<param>=<val>
458Params: speed Display SPI bus speed
459
460 rotate Display rotation {0,90,180,270}
461
462 fps Delay between frame updates
463
464 debug Debug output level {0-7}
465
466 xohms Touchpanel sensitivity (X-plate resistance)
467
468 resetgpio GPIO used to reset controller
469
470 ledgpio GPIO used to control backlight
471
472
473Name: i2c-bcm2708
474Info: Fall back to the i2c_bcm2708 driver for the i2c_arm bus.
475Load: dtoverlay=i2c-bcm2708
476Params: <None>
477
478
479Name: i2c-gpio
480Info: Adds support for software i2c controller on gpio pins
481Load: dtoverlay=i2c-gpio,<param>=<val>
482Params: i2c_gpio_sda GPIO used for I2C data (default "23")
483
484 i2c_gpio_scl GPIO used for I2C clock (default "24")
485
486 i2c_gpio_delay_us Clock delay in microseconds
487 (default "2" = ~100kHz)
488
489
490Name: i2c-mux
491Info: Adds support for a number of I2C bus multiplexers on i2c_arm
492Load: dtoverlay=i2c-mux,<param>=<val>
493Params: pca9542 Select the NXP PCA9542 device
494
495 pca9545 Select the NXP PCA9545 device
496
497 pca9548 Select the NXP PCA9548 device
498
499 addr Change I2C address of the device (default 0x70)
500
501
502[ The i2c-mux-pca9548a overlay has been deleted. See i2c-mux. ]
503
504
505Name: i2c-pwm-pca9685a
506Info: Adds support for an NXP PCA9685A I2C PWM controller on i2c_arm
507Load: dtoverlay=i2c-pwm-pca9685a,<param>=<val>
508Params: addr I2C address of PCA9685A (default 0x40)
509
510
511Name: i2c-rtc
512Info: Adds support for a number of I2C Real Time Clock devices
513Load: dtoverlay=i2c-rtc,<param>=<val>
514Params: abx80x Select one of the ABx80x family:
515 AB0801, AB0803, AB0804, AB0805,
516 AB1801, AB1803, AB1804, AB1805
517
518 ds1307 Select the DS1307 device
519
520 ds1339 Select the DS1339 device
521
522 ds3231 Select the DS3231 device
523
524 mcp7940x Select the MCP7940x device
525
526 mcp7941x Select the MCP7941x device
527
528 pcf2127 Select the PCF2127 device
529
530 pcf8523 Select the PCF8523 device
531
532 pcf8563 Select the PCF8563 device
533
534 trickle-diode-type Diode type for trickle charge - "standard" or
535 "schottky" (ABx80x only)
536
537 trickle-resistor-ohms Resistor value for trickle charge (DS1339,
538 ABx80x)
539
540 wakeup-source Specify that the RTC can be used as a wakeup
541 source
542
543
544Name: i2c-sensor
545Info: Adds support for a number of I2C barometric pressure and temperature
546 sensors on i2c_arm
547Load: dtoverlay=i2c-sensor,<param>=<val>
548Params: bmp085 Select the Bosch sensortronic BMP085
549
550 bmp280 Select the Bosch sensortronic BMP280
551
552
553Name: i2c0-bcm2708
554Info: Enable the i2c_bcm2708 driver for the i2c0 bus. Not all pin combinations
555 are usable on all platforms.
556Load: dtoverlay=i2c0-bcm2708,<param>=<val>
557Params: sda0_pin GPIO pin for SDA0 (deprecated - use pins_*)
558 scl0_pin GPIO pin for SCL0 (deprecated - use pins_*)
559 pins_0_1 Use pins 0 and 1 (default)
560 pins_28_29 Use pins 28 and 29
561 pins_44_45 Use pins 44 and 45
562 pins_46_47 Use pins 46 and 47
563
564
565Name: i2c1-bcm2708
566Info: Enable the i2c_bcm2708 driver for the i2c1 bus
567Load: dtoverlay=i2c1-bcm2708,<param>=<val>
568Params: sda1_pin GPIO pin for SDA1 (2 or 44 - default 2)
569 scl1_pin GPIO pin for SCL1 (3 or 45 - default 3)
570 pin_func Alternative pin function (4 (alt0), 6 (alt2) -
571 default 4)
572
573
574Name: i2s-gpio28-31
575Info: move I2S function block to GPIO 28 to 31
576Load: dtoverlay=i2s-gpio28-31
577Params: <None>
578
579
580Name: iqaudio-dac
581Info: Configures the IQaudio DAC audio card
582Load: dtoverlay=iqaudio-dac,<param>
583Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
584 Digital volume control. Enable with
585 "dtoverlay=iqaudio-dac,24db_digital_gain"
586 (The default behaviour is that the Digital
587 volume control is limited to a maximum of
588 0dB. ie. it can attenuate but not provide
589 gain. For most users, this will be desired
590 as it will prevent clipping. By appending
591 the 24db_digital_gain parameter, the Digital
592 volume control will allow up to 24dB of
593 gain. If this parameter is enabled, it is the
594 responsibility of the user to ensure that
595 the Digital volume control is set to a value
596 that does not result in clipping/distortion!)
597
598
599Name: iqaudio-dacplus
600Info: Configures the IQaudio DAC+ audio card
601Load: dtoverlay=iqaudio-dacplus,<param>=<val>
602Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
603 Digital volume control. Enable with
604 "dtoverlay=iqaudio-dacplus,24db_digital_gain"
605 (The default behaviour is that the Digital
606 volume control is limited to a maximum of
607 0dB. ie. it can attenuate but not provide
608 gain. For most users, this will be desired
609 as it will prevent clipping. By appending
610 the 24db_digital_gain parameter, the Digital
611 volume control will allow up to 24dB of
612 gain. If this parameter is enabled, it is the
613 responsibility of the user to ensure that
614 the Digital volume control is set to a value
615 that does not result in clipping/distortion!)
616 auto_mute_amp If specified, unmute/mute the IQaudIO amp when
617 starting/stopping audio playback.
618 unmute_amp If specified, unmute the IQaudIO amp once when
619 the DAC driver module loads.
620
621
622Name: iqaudio-digi-wm8804-audio
623Info: Configures the IQAudIO Digi WM8804 audio card
624Load: dtoverlay=iqaudio-digi-wm8804-audio,<param>=<val>
625Params: card_name Override the default, "IQAudIODigi", card name.
626 dai_name Override the default, "IQAudIO Digi", dai name.
627 dai_stream_name Override the default, "IQAudIO Digi HiFi",
628 dai stream name.
629
630
631Name: justboom-dac
632Info: Configures the JustBoom DAC HAT, Amp HAT, DAC Zero and Amp Zero audio
633 cards
634Load: dtoverlay=justboom-dac,<param>=<val>
635Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
636 Digital volume control. Enable with
637 "dtoverlay=justboom-dac,24db_digital_gain"
638 (The default behaviour is that the Digital
639 volume control is limited to a maximum of
640 0dB. ie. it can attenuate but not provide
641 gain. For most users, this will be desired
642 as it will prevent clipping. By appending
643 the 24dB_digital_gain parameter, the Digital
644 volume control will allow up to 24dB of
645 gain. If this parameter is enabled, it is the
646 responsibility of the user to ensure that
647 the Digital volume control is set to a value
648 that does not result in clipping/distortion!)
649
650
651Name: justboom-digi
652Info: Configures the JustBoom Digi HAT and Digi Zero audio cards
653Load: dtoverlay=justboom-digi
654Params: <None>
655
656
657Name: lirc-rpi
658Info: Configures lirc-rpi (Linux Infrared Remote Control for Raspberry Pi)
659 Consult the module documentation for more details.
660Load: dtoverlay=lirc-rpi,<param>=<val>
661Params: gpio_out_pin GPIO for output (default "17")
662
663 gpio_in_pin GPIO for input (default "18")
664
665 gpio_in_pull Pull up/down/off on the input pin
666 (default "down")
667
668 sense Override the IR receive auto-detection logic:
669 "0" = force active-high
670 "1" = force active-low
671 "-1" = use auto-detection
672 (default "-1")
673
674 softcarrier Turn the software carrier "on" or "off"
675 (default "on")
676
677 invert "on" = invert the output pin (default "off")
678
679 debug "on" = enable additional debug messages
680 (default "off")
681
682
683Name: mcp23017
684Info: Configures the MCP23017 I2C GPIO expander
685Load: dtoverlay=mcp23017,<param>=<val>
686Params: gpiopin Gpio pin connected to the INTA output of the
687 MCP23017 (default: 4)
688
689 addr I2C address of the MCP23017 (default: 0x20)
690
691
692Name: mcp23s17
693Info: Configures the MCP23S08/17 SPI GPIO expanders.
694 If devices are present on SPI1 or SPI2, those interfaces must be enabled
695 with one of the spi1-1/2/3cs and/or spi2-1/2/3cs overlays.
696 If interrupts are enabled for a device on a given CS# on a SPI bus, that
697 device must be the only one present on that SPI bus/CS#.
698Load: dtoverlay=mcp23s17,<param>=<val>
699Params: s08-spi<n>-<m>-present 4-bit integer, bitmap indicating MCP23S08
700 devices present on SPI<n>, CS#<m>
701
702 s17-spi<n>-<m>-present 8-bit integer, bitmap indicating MCP23S17
703 devices present on SPI<n>, CS#<m>
704
705 s08-spi<n>-<m>-int-gpio integer, enables interrupts on a single
706 MCP23S08 device on SPI<n>, CS#<m>, specifies
707 the GPIO pin to which INT output of MCP23S08
708 is connected.
709
710 s17-spi<n>-<m>-int-gpio integer, enables mirrored interrupts on a
711 single MCP23S17 device on SPI<n>, CS#<m>,
712 specifies the GPIO pin to which either INTA
713 or INTB output of MCP23S17 is connected.
714
715
716Name: mcp2515-can0
717Info: Configures the MCP2515 CAN controller on spi0.0
718Load: dtoverlay=mcp2515-can0,<param>=<val>
719Params: oscillator Clock frequency for the CAN controller (Hz)
720
721 spimaxfrequency Maximum SPI frequence (Hz)
722
723 interrupt GPIO for interrupt signal
724
725
726Name: mcp2515-can1
727Info: Configures the MCP2515 CAN controller on spi0.1
728Load: dtoverlay=mcp2515-can1,<param>=<val>
729Params: oscillator Clock frequency for the CAN controller (Hz)
730
731 spimaxfrequency Maximum SPI frequence (Hz)
732
733 interrupt GPIO for interrupt signal
734
735
736Name: midi-uart0
737Info: Configures UART0 (ttyAMA0) so that a requested 38.4kbaud actually gets
738 31.25kbaud, the frequency required for MIDI
739Load: dtoverlay=midi-uart0
740Params: <None>
741
742
743Name: mmc
744Info: Selects the bcm2835-mmc SD/MMC driver, optionally with overclock
745Load: dtoverlay=mmc,<param>=<val>
746Params: overclock_50 Clock (in MHz) to use when the MMC framework
747 requests 50MHz
748
749
750Name: mz61581
751Info: MZ61581 display by Tontec
752Load: dtoverlay=mz61581,<param>=<val>
753Params: speed Display SPI bus speed
754
755 rotate Display rotation {0,90,180,270}
756
757 fps Delay between frame updates
758
759 txbuflen Transmit buffer length (default 32768)
760
761 debug Debug output level {0-7}
762
763 xohms Touchpanel sensitivity (X-plate resistance)
764
765
766[ The pcf2127-rtc overlay has been deleted. See i2c-rtc. ]
767
768
769[ The pcf8523-rtc overlay has been deleted. See i2c-rtc. ]
770
771
772[ The pcf8563-rtc overlay has been deleted. See i2c-rtc. ]
773
774
775Name: pi3-act-led
776Info: Pi3 uses a GPIO expander to drive the LEDs which can only be accessed
777 from the VPU. There is a special driver for this with a separate DT
778 node, which has the unfortunate consequence of breaking the
779 act_led_gpio and act_led_activelow dtparams.
780 This overlay changes the GPIO controller back to the standard one and
781 restores the dtparams.
782Load: dtoverlay=pi3-act-led,<param>=<val>
783Params: activelow Set to "on" to invert the sense of the LED
784 (default "off")
785
786 gpio Set which GPIO to use for the activity LED
787 (in case you want to connect it to an external
788 device)
789 REQUIRED
790
791
792Name: pi3-disable-bt
793Info: Disable Pi3 Bluetooth and restore UART0/ttyAMA0 over GPIOs 14 & 15
794 N.B. To disable the systemd service that initialises the modem so it
795 doesn't use the UART, use 'sudo systemctl disable hciuart'.
796Load: dtoverlay=pi3-disable-bt
797Params: <None>
798
799
800Name: pi3-miniuart-bt
801Info: Switch Pi3 Bluetooth function to use the mini-UART (ttyS0) and restore
802 UART0/ttyAMA0 over GPIOs 14 & 15. Note that this may reduce the maximum
803 usable baudrate.
804 N.B. It is also necessary to edit /lib/systemd/system/hciuart.service
805 and replace ttyAMA0 with ttyS0, unless you have a system with udev rules
806 that create /dev/serial0 and /dev/serial1, in which case use
807 /dev/serial1 instead because it will always be correct. Furthermore,
808 you must also set core_freq=250 in config.txt or the miniuart will not
809 work.
810Load: dtoverlay=pi3-miniuart-bt
811Params: <None>
812
813
814Name: piscreen
815Info: PiScreen display by OzzMaker.com
816Load: dtoverlay=piscreen,<param>=<val>
817Params: speed Display SPI bus speed
818
819 rotate Display rotation {0,90,180,270}
820
821 fps Delay between frame updates
822
823 debug Debug output level {0-7}
824
825 xohms Touchpanel sensitivity (X-plate resistance)
826
827
828Name: piscreen2r
829Info: PiScreen 2 with resistive TP display by OzzMaker.com
830Load: dtoverlay=piscreen2r,<param>=<val>
831Params: speed Display SPI bus speed
832
833 rotate Display rotation {0,90,180,270}
834
835 fps Delay between frame updates
836
837 debug Debug output level {0-7}
838
839 xohms Touchpanel sensitivity (X-plate resistance)
840
841
842Name: pisound
843Info: Configures the Blokas Labs pisound card
844Load: dtoverlay=pisound
845Params: <None>
846
847
848Name: pitft22
849Info: Adafruit PiTFT 2.2" screen
850Load: dtoverlay=pitft22,<param>=<val>
851Params: speed Display SPI bus speed
852
853 rotate Display rotation {0,90,180,270}
854
855 fps Delay between frame updates
856
857 debug Debug output level {0-7}
858
859
860Name: pitft28-capacitive
861Info: Adafruit PiTFT 2.8" capacitive touch screen
862Load: dtoverlay=pitft28-capacitive,<param>=<val>
863Params: speed Display SPI bus speed
864
865 rotate Display rotation {0,90,180,270}
866
867 fps Delay between frame updates
868
869 debug Debug output level {0-7}
870
871 touch-sizex Touchscreen size x (default 240)
872
873 touch-sizey Touchscreen size y (default 320)
874
875 touch-invx Touchscreen inverted x axis
876
877 touch-invy Touchscreen inverted y axis
878
879 touch-swapxy Touchscreen swapped x y axis
880
881
882Name: pitft28-resistive
883Info: Adafruit PiTFT 2.8" resistive touch screen
884Load: dtoverlay=pitft28-resistive,<param>=<val>
885Params: speed Display SPI bus speed
886
887 rotate Display rotation {0,90,180,270}
888
889 fps Delay between frame updates
890
891 debug Debug output level {0-7}
892
893
894Name: pitft35-resistive
895Info: Adafruit PiTFT 3.5" resistive touch screen
896Load: dtoverlay=pitft35-resistive,<param>=<val>
897Params: speed Display SPI bus speed
898
899 rotate Display rotation {0,90,180,270}
900
901 fps Delay between frame updates
902
903 debug Debug output level {0-7}
904
905
906Name: pps-gpio
907Info: Configures the pps-gpio (pulse-per-second time signal via GPIO).
908Load: dtoverlay=pps-gpio,<param>=<val>
909Params: gpiopin Input GPIO (default "18")
910 assert_falling_edge When present, assert is indicated by a falling
911 edge, rather than by a rising edge
912
913
914Name: pwm
915Info: Configures a single PWM channel
916 Legal pin,function combinations for each channel:
917 PWM0: 12,4(Alt0) 18,2(Alt5) 40,4(Alt0) 52,5(Alt1)
918 PWM1: 13,4(Alt0) 19,2(Alt5) 41,4(Alt0) 45,4(Alt0) 53,5(Alt1)
919 N.B.:
920 1) Pin 18 is the only one available on all platforms, and
921 it is the one used by the I2S audio interface.
922 Pins 12 and 13 might be better choices on an A+, B+ or Pi2.
923 2) The onboard analogue audio output uses both PWM channels.
924 3) So be careful mixing audio and PWM.
925 4) Currently the clock must have been enabled and configured
926 by other means.
927Load: dtoverlay=pwm,<param>=<val>
928Params: pin Output pin (default 18) - see table
929 func Pin function (default 2 = Alt5) - see above
930 clock PWM clock frequency (informational)
931
932
933Name: pwm-2chan
934Info: Configures both PWM channels
935 Legal pin,function combinations for each channel:
936 PWM0: 12,4(Alt0) 18,2(Alt5) 40,4(Alt0) 52,5(Alt1)
937 PWM1: 13,4(Alt0) 19,2(Alt5) 41,4(Alt0) 45,4(Alt0) 53,5(Alt1)
938 N.B.:
939 1) Pin 18 is the only one available on all platforms, and
940 it is the one used by the I2S audio interface.
941 Pins 12 and 13 might be better choices on an A+, B+ or Pi2.
942 2) The onboard analogue audio output uses both PWM channels.
943 3) So be careful mixing audio and PWM.
944 4) Currently the clock must have been enabled and configured
945 by other means.
946Load: dtoverlay=pwm-2chan,<param>=<val>
947Params: pin Output pin (default 18) - see table
948 pin2 Output pin for other channel (default 19)
949 func Pin function (default 2 = Alt5) - see above
950 func2 Function for pin2 (default 2 = Alt5)
951 clock PWM clock frequency (informational)
952
953
954Name: qca7000
955Info: I2SE's Evaluation Board for PLC Stamp micro
956Load: dtoverlay=qca7000,<param>=<val>
957Params: int_pin GPIO pin for interrupt signal (default 23)
958
959 speed SPI bus speed (default 12 MHz)
960
961
962Name: raspidac3
963Info: Configures the RaspiDAV Rev.3x audio card
964Load: dtoverlay=raspidac3
965Params: <None>
966
967
968Name: rpi-backlight
969Info: Raspberry Pi official display backlight driver
970Load: dtoverlay=rpi-backlight
971Params: <None>
972
973
974Name: rpi-dac
975Info: Configures the RPi DAC audio card
976Load: dtoverlay=rpi-dac
977Params: <None>
978
979
980Name: rpi-display
981Info: RPi-Display - 2.8" Touch Display by Watterott
982Load: dtoverlay=rpi-display,<param>=<val>
983Params: speed Display SPI bus speed
984 rotate Display rotation {0,90,180,270}
985 fps Delay between frame updates
986 debug Debug output level {0-7}
987 xohms Touchpanel sensitivity (X-plate resistance)
988 swapxy Swap x and y axis
989
990
991Name: rpi-ft5406
992Info: Official Raspberry Pi display touchscreen
993Load: dtoverlay=rpi-ft5406
994Params: <None>
995
996
997Name: rpi-proto
998Info: Configures the RPi Proto audio card
999Load: dtoverlay=rpi-proto
1000Params: <None>
1001
1002
1003Name: rpi-sense
1004Info: Raspberry Pi Sense HAT
1005Load: dtoverlay=rpi-sense
1006Params: <None>
1007
1008
1009Name: rra-digidac1-wm8741-audio
1010Info: Configures the Red Rocks Audio DigiDAC1 soundcard
1011Load: dtoverlay=rra-digidac1-wm8741-audio
1012Params: <None>
1013
1014
1015Name: sc16is750-i2c
1016Info: Overlay for the NXP SC16IS750 UART with I2C Interface
1017 Enables the chip on I2C1 at 0x48. To select another address,
1018 please refer to table 10 in reference manual.
1019
1020Load: dtoverlay=sc16is750-i2c,<param>=<val>
1021Params: int_pin GPIO used for IRQ (default 24)
1022 addr Address (default 0x48)
1023
1024
1025Name: sc16is752-spi1
1026Info: Overlay for the NXP SC16IS752 Dual UART with SPI Interface
1027 Enables the chip on SPI1.
1028 N.B.: spi1 is only accessible on devices with a 40pin header, eg:
1029 A+, B+, Zero and PI2 B; as well as the Compute Module.
1030
1031Load: dtoverlay=sc16is752-spi1,<param>=<val>
1032Params: int_pin GPIO used for IRQ (default 24)
1033
1034
1035Name: sdhost
1036Info: Selects the bcm2835-sdhost SD/MMC driver, optionally with overclock.
1037 N.B. This overlay is designed for situations where the mmc driver is
1038 the default, so it disables the other (mmc) interface - this will kill
1039 WiFi on a Pi3. If this isn't what you want, either use the sdtweak
1040 overlay or the new sd_* dtparams of the base DTBs.
1041Load: dtoverlay=sdhost,<param>=<val>
1042Params: overclock_50 Clock (in MHz) to use when the MMC framework
1043 requests 50MHz
1044
1045 force_pio Disable DMA support (default off)
1046
1047 pio_limit Number of blocks above which to use DMA
1048 (default 1)
1049
1050 debug Enable debug output (default off)
1051
1052
1053Name: sdio
1054Info: Selects the bcm2835-sdhost SD/MMC driver, optionally with overclock,
1055 and enables SDIO via GPIOs 22-27.
1056Load: dtoverlay=sdio,<param>=<val>
1057Params: overclock_50 SD Clock (in MHz) to use when the MMC framework
1058 requests 50MHz
1059
1060 sdio_overclock SDIO Clock (in MHz) to use when the MMC
1061 framework requests 50MHz
1062
1063 force_pio Disable DMA support (default off)
1064
1065 pio_limit Number of blocks above which to use DMA
1066 (default 1)
1067
1068 debug Enable debug output (default off)
1069
1070 poll_once Disable SDIO-device polling every second
1071 (default on: polling once at boot-time)
1072
1073 bus_width Set the SDIO host bus width (default 4 bits)
1074
1075
1076Name: sdio-1bit
1077Info: Selects the bcm2835-sdhost SD/MMC driver, optionally with overclock,
1078 and enables 1-bit SDIO via GPIOs 22-25.
1079Load: dtoverlay=sdio-1bit,<param>=<val>
1080Params: overclock_50 SD Clock (in MHz) to use when the MMC framework
1081 requests 50MHz
1082
1083 sdio_overclock SDIO Clock (in MHz) to use when the MMC
1084 framework requests 50MHz
1085
1086 force_pio Disable DMA support (default off)
1087
1088 pio_limit Number of blocks above which to use DMA
1089 (default 1)
1090
1091 debug Enable debug output (default off)
1092
1093 poll_once Disable SDIO-device polling every second
1094 (default on: polling once at boot-time)
1095
1096
1097Name: sdtweak
1098Info: Tunes the bcm2835-sdhost SD/MMC driver
1099 N.B. This functionality is now available via the sd_* dtparams in the
1100 base DTB.
1101Load: dtoverlay=sdtweak,<param>=<val>
1102Params: overclock_50 Clock (in MHz) to use when the MMC framework
1103 requests 50MHz
1104
1105 force_pio Disable DMA support (default off)
1106
1107 pio_limit Number of blocks above which to use DMA
1108 (default 1)
1109
1110 debug Enable debug output (default off)
1111
1112
1113Name: smi
1114Info: Enables the Secondary Memory Interface peripheral. Uses GPIOs 2-25!
1115Load: dtoverlay=smi
1116Params: <None>
1117
1118
1119Name: smi-dev
1120Info: Enables the userspace interface for the SMI driver
1121Load: dtoverlay=smi-dev
1122Params: <None>
1123
1124
1125Name: smi-nand
1126Info: Enables access to NAND flash via the SMI interface
1127Load: dtoverlay=smi-nand
1128Params: <None>
1129
1130
1131Name: spi-gpio35-39
1132Info: move SPI function block to GPIO 35 to 39
1133Load: dtoverlay=spi-gpio35-39
1134Params: <None>
1135
1136
1137Name: spi-rtc
1138Info: Adds support for a number of SPI Real Time Clock devices
1139Load: dtoverlay=spi-rtc,<param>=<val>
1140Params: pcf2123 Select the PCF2123 device
1141
1142
1143Name: spi0-hw-cs
1144Info: Re-enables hardware CS/CE (chip selects) for SPI0
1145Load: dtoverlay=spi0-hw-cs
1146Params: <None>
1147
1148
1149Name: spi1-1cs
1150Info: Enables spi1 with a single chip select (CS) line and associated spidev
1151 dev node. The gpio pin number for the CS line and spidev device node
1152 creation are configurable.
1153 N.B.: spi1 is only accessible on devices with a 40pin header, eg:
1154 A+, B+, Zero and PI2 B; as well as the Compute Module.
1155Load: dtoverlay=spi1-1cs,<param>=<val>
1156Params: cs0_pin GPIO pin for CS0 (default 18 - BCM SPI1_CE0).
1157 cs0_spidev Set to 'disabled' to stop the creation of a
1158 userspace device node /dev/spidev1.0 (default
1159 is 'okay' or enabled).
1160
1161
1162Name: spi1-2cs
1163Info: Enables spi1 with two chip select (CS) lines and associated spidev
1164 dev nodes. The gpio pin numbers for the CS lines and spidev device node
1165 creation are configurable.
1166 N.B.: spi1 is only accessible on devices with a 40pin header, eg:
1167 A+, B+, Zero and PI2 B; as well as the Compute Module.
1168Load: dtoverlay=spi1-2cs,<param>=<val>
1169Params: cs0_pin GPIO pin for CS0 (default 18 - BCM SPI1_CE0).
1170 cs1_pin GPIO pin for CS1 (default 17 - BCM SPI1_CE1).
1171 cs0_spidev Set to 'disabled' to stop the creation of a
1172 userspace device node /dev/spidev1.0 (default
1173 is 'okay' or enabled).
1174 cs1_spidev Set to 'disabled' to stop the creation of a
1175 userspace device node /dev/spidev1.1 (default
1176 is 'okay' or enabled).
1177
1178
1179Name: spi1-3cs
1180Info: Enables spi1 with three chip select (CS) lines and associated spidev
1181 dev nodes. The gpio pin numbers for the CS lines and spidev device node
1182 creation are configurable.
1183 N.B.: spi1 is only accessible on devices with a 40pin header, eg:
1184 A+, B+, Zero and PI2 B; as well as the Compute Module.
1185Load: dtoverlay=spi1-3cs,<param>=<val>
1186Params: cs0_pin GPIO pin for CS0 (default 18 - BCM SPI1_CE0).
1187 cs1_pin GPIO pin for CS1 (default 17 - BCM SPI1_CE1).
1188 cs2_pin GPIO pin for CS2 (default 16 - BCM SPI1_CE2).
1189 cs0_spidev Set to 'disabled' to stop the creation of a
1190 userspace device node /dev/spidev1.0 (default
1191 is 'okay' or enabled).
1192 cs1_spidev Set to 'disabled' to stop the creation of a
1193 userspace device node /dev/spidev1.1 (default
1194 is 'okay' or enabled).
1195 cs2_spidev Set to 'disabled' to stop the creation of a
1196 userspace device node /dev/spidev1.2 (default
1197 is 'okay' or enabled).
1198
1199
1200Name: spi2-1cs
1201Info: Enables spi2 with a single chip select (CS) line and associated spidev
1202 dev node. The gpio pin number for the CS line and spidev device node
1203 creation are configurable.
1204 N.B.: spi2 is only accessible with the Compute Module.
1205Load: dtoverlay=spi2-1cs,<param>=<val>
1206Params: cs0_pin GPIO pin for CS0 (default 43 - BCM SPI2_CE0).
1207 cs0_spidev Set to 'disabled' to stop the creation of a
1208 userspace device node /dev/spidev2.0 (default
1209 is 'okay' or enabled).
1210
1211
1212Name: spi2-2cs
1213Info: Enables spi2 with two chip select (CS) lines and associated spidev
1214 dev nodes. The gpio pin numbers for the CS lines and spidev device node
1215 creation are configurable.
1216 N.B.: spi2 is only accessible with the Compute Module.
1217Load: dtoverlay=spi2-2cs,<param>=<val>
1218Params: cs0_pin GPIO pin for CS0 (default 43 - BCM SPI2_CE0).
1219 cs1_pin GPIO pin for CS1 (default 44 - BCM SPI2_CE1).
1220 cs0_spidev Set to 'disabled' to stop the creation of a
1221 userspace device node /dev/spidev2.0 (default
1222 is 'okay' or enabled).
1223 cs1_spidev Set to 'disabled' to stop the creation of a
1224 userspace device node /dev/spidev2.1 (default
1225 is 'okay' or enabled).
1226
1227
1228Name: spi2-3cs
1229Info: Enables spi2 with three chip select (CS) lines and associated spidev
1230 dev nodes. The gpio pin numbers for the CS lines and spidev device node
1231 creation are configurable.
1232 N.B.: spi2 is only accessible with the Compute Module.
1233Load: dtoverlay=spi2-3cs,<param>=<val>
1234Params: cs0_pin GPIO pin for CS0 (default 43 - BCM SPI2_CE0).
1235 cs1_pin GPIO pin for CS1 (default 44 - BCM SPI2_CE1).
1236 cs2_pin GPIO pin for CS2 (default 45 - BCM SPI2_CE2).
1237 cs0_spidev Set to 'disabled' to stop the creation of a
1238 userspace device node /dev/spidev2.0 (default
1239 is 'okay' or enabled).
1240 cs1_spidev Set to 'disabled' to stop the creation of a
1241 userspace device node /dev/spidev2.1 (default
1242 is 'okay' or enabled).
1243 cs2_spidev Set to 'disabled' to stop the creation of a
1244 userspace device node /dev/spidev2.2 (default
1245 is 'okay' or enabled).
1246
1247
1248Name: tinylcd35
1249Info: 3.5" Color TFT Display by www.tinylcd.com
1250 Options: Touch, RTC, keypad
1251Load: dtoverlay=tinylcd35,<param>=<val>
1252Params: speed Display SPI bus speed
1253
1254 rotate Display rotation {0,90,180,270}
1255
1256 fps Delay between frame updates
1257
1258 debug Debug output level {0-7}
1259
1260 touch Enable touch panel
1261
1262 touchgpio Touch controller IRQ GPIO
1263
1264 xohms Touchpanel: Resistance of X-plate in ohms
1265
1266 rtc-pcf PCF8563 Real Time Clock
1267
1268 rtc-ds DS1307 Real Time Clock
1269
1270 keypad Enable keypad
1271
1272 Examples:
1273 Display with touchpanel, PCF8563 RTC and keypad:
1274 dtoverlay=tinylcd35,touch,rtc-pcf,keypad
1275 Old touch display:
1276 dtoverlay=tinylcd35,touch,touchgpio=3
1277
1278
1279Name: uart1
1280Info: Enable uart1 in place of uart0
1281Load: dtoverlay=uart1,<param>=<val>
1282Params: txd1_pin GPIO pin for TXD1 (14, 32 or 40 - default 14)
1283
1284 rxd1_pin GPIO pin for RXD1 (15, 33 or 41 - default 15)
1285
1286
1287Name: vc4-fkms-v3d
1288Info: Enable Eric Anholt's DRM VC4 V3D driver on top of the dispmanx
1289 display stack.
1290Load: dtoverlay=vc4-fkms-v3d,<param>
1291Params: cma-256 CMA is 256MB, 256MB-aligned (needs 1GB)
1292 cma-192 CMA is 192MB, 256MB-aligned (needs 1GB)
1293 cma-128 CMA is 128MB, 128MB-aligned
1294 cma-96 CMA is 96MB, 128MB-aligned
1295 cma-64 CMA is 64MB, 64MB-aligned
1296
1297
1298Name: vc4-kms-v3d
1299Info: Enable Eric Anholt's DRM VC4 HDMI/HVS/V3D driver. Running startx or
1300 booting to GUI while this overlay is in use will cause interesting
1301 lockups.
1302Load: dtoverlay=vc4-kms-v3d,<param>
1303Params: cma-256 CMA is 256MB, 256MB-aligned (needs 1GB)
1304 cma-192 CMA is 192MB, 256MB-aligned (needs 1GB)
1305 cma-128 CMA is 128MB, 128MB-aligned
1306 cma-96 CMA is 96MB, 128MB-aligned
1307 cma-64 CMA is 64MB, 64MB-aligned
1308
1309
1310Name: vga666
1311Info: Overlay for the Fen Logic VGA666 board
1312 This uses GPIOs 2-21 (so no I2C), and activates the output 2-3 seconds
1313 after the kernel has started.
1314Load: dtoverlay=vga666
1315Params: <None>
1316
1317
1318Name: w1-gpio
1319Info: Configures the w1-gpio Onewire interface module.
1320 Use this overlay if you *don't* need a GPIO to drive an external pullup.
1321Load: dtoverlay=w1-gpio,<param>=<val>
1322Params: gpiopin GPIO for I/O (default "4")
1323
1324 pullup Non-zero, "on", or "y" to enable the parasitic
1325 power (2-wire, power-on-data) feature
1326
1327
1328Name: w1-gpio-pullup
1329Info: Configures the w1-gpio Onewire interface module.
1330 Use this overlay if you *do* need a GPIO to drive an external pullup.
1331Load: dtoverlay=w1-gpio-pullup,<param>=<val>
1332Params: gpiopin GPIO for I/O (default "4")
1333
1334 pullup Non-zero, "on", or "y" to enable the parasitic
1335 power (2-wire, power-on-data) feature
1336
1337 extpullup GPIO for external pullup (default "5")
1338
1339
1340Name: wittypi
1341Info: Configures the wittypi RTC module.
1342Load: dtoverlay=wittypi,<param>=<val>
1343Params: led_gpio GPIO for LED (default "17")
1344 led_trigger Choose which activity the LED tracks (default
1345 "default-on")
1346
1347
1348Troubleshooting
1349===============
1350
1351If you are experiencing problems that you think are DT-related, enable DT
1352diagnostic output by adding this to /boot/config.txt:
1353
1354 dtdebug=on
1355
1356and rebooting. Then run:
1357
1358 sudo vcdbg log msg
1359
1360and look for relevant messages.
1361
1362Further reading
1363===============
1364
1365This is only meant to be a quick introduction to the subject of Device Tree on
1366Raspberry Pi. There is a more complete explanation here:
1367
1368http://www.raspberrypi.org/documentation/configuration/device-tree.md
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