Documentation/media/v4l-drivers/cx88.rst

   1 The cx88 driver
   2 ===============
   3
   4 Author:  Gerd Hoffmann
   5
   6 This is a v4l2 device driver for the cx2388x chip.
   7
   8
   9 Current status
  10 --------------
  11
  12 video
  13         - Works.
  14         - Overlay isn't supported.
  15
  16 audio
  17         - Works. The TV standard detection is made by the driver, as the
  18           hardware has bugs to auto-detect.
  19         - audio data dma (i.e. recording without loopback cable to the
  20           sound card) is supported via cx88-alsa.
  21
  22 vbi
  23         - Works.
  24
  25
  26 How to add support for new cards
  27 --------------------------------
  28
  29 The driver needs some config info for the TV cards.  This stuff is in
  30 cx88-cards.c.  If the driver doesn't work well you likely need a new
  31 entry for your card in that file.  Check the kernel log (using dmesg)
  32 to see whenever the driver knows your card or not.  There is a line
  33 like this one:
  34
  35 .. code-block:: none
  36
  37         cx8800[0]: subsystem: 0070:3400, board: Hauppauge WinTV \
  38                 34xxx models [card=1,autodetected]
  39
  40 If your card is listed as "board: UNKNOWN/GENERIC" it is unknown to
  41 the driver.  What to do then?
  42
  43 1) Try upgrading to the latest snapshot, maybe it has been added
  44    meanwhile.
  45 2) You can try to create a new entry yourself, have a look at
  46    cx88-cards.c.  If that worked, mail me your changes as unified
  47    diff ("diff -u").
  48 3) Or you can mail me the config information.  We need at least the
  49    following information to add the card:
  50
  51      - the PCI Subsystem ID ("0070:3400" from the line above,
  52        "lspci -v" output is fine too).
  53      - the tuner type used by the card.  You can try to find one by
  54        trial-and-error using the tuner=<n> insmod option.  If you
  55        know which one the card has you can also have a look at the
  56        list in CARDLIST.tuner
  57
  58 Documentation missing at the cx88 datasheet
  59 -------------------------------------------
  60
  61 MO_OUTPUT_FORMAT (0x310164)
  62
  63 .. code-block:: none
  64
  65   Previous default from DScaler: 0x1c1f0008
  66   Digit 8: 31-28
  67   28: PREVREMOD = 1
  68
  69   Digit 7: 27-24 (0xc = 12 = b1100 )
  70   27: COMBALT = 1
  71   26: PAL_INV_PHASE
  72     (DScaler apparently set this to 1, resulted in sucky picture)
  73
  74   Digits 6,5: 23-16
  75   25-16: COMB_RANGE = 0x1f [default] (9 bits -> max 512)
  76
  77   Digit 4: 15-12
  78   15: DISIFX = 0
  79   14: INVCBF = 0
  80   13: DISADAPT = 0
  81   12: NARROWADAPT = 0
  82
  83   Digit 3: 11-8
  84   11: FORCE2H
  85   10: FORCEREMD
  86   9: NCHROMAEN
  87   8: NREMODEN
  88
  89   Digit 2: 7-4
  90   7-6: YCORE
  91   5-4: CCORE
  92
  93   Digit 1: 3-0
  94   3: RANGE = 1
  95   2: HACTEXT
  96   1: HSFMT
  97
  98 0x47 is the sync byte for MPEG-2 transport stream packets.
  99 Datasheet incorrectly states to use 47 decimal. 188 is the length.
 100 All DVB compliant frontends output packets with this start code.
 101
 102 Hauppauge WinTV cx88 IR information
 103 -----------------------------------
 104
 105 The controls for the mux are GPIO [0,1] for source, and GPIO 2 for muting.
 106
 107 ====== ======== =================================================
 108 GPIO0  GPIO1
 109 ====== ======== =================================================
 110   0        0    TV Audio
 111   1        0    FM radio
 112   0        1    Line-In
 113   1        1    Mono tuner bypass or CD passthru (tuner specific)
 114 ====== ======== =================================================
 115
 116 GPIO 16(I believe) is tied to the IR port (if present).
 117
 118
 119 From the data sheet:
 120
 121 - Register 24'h20004  PCI Interrupt Status
 122
 123  - bit [18]  IR_SMP_INT Set when 32 input samples have been collected over
 124  - gpio[16] pin into GP_SAMPLE register.
 125
 126 What's missing from the data sheet:
 127
 128 - Setup 4KHz sampling rate (roughly 2x oversampled; good enough for our RC5
 129   compat remote)
 130 - set register 0x35C050 to  0xa80a80
 131 - enable sampling
 132 - set register 0x35C054 to 0x5
 133 - enable the IRQ bit 18 in the interrupt mask register (and
 134   provide for a handler)
 135
 136 GP_SAMPLE register is at 0x35C058
 137
 138 Bits are then right shifted into the GP_SAMPLE register at the specified
 139 rate; you get an interrupt when a full DWORD is received.
 140 You need to recover the actual RC5 bits out of the (oversampled) IR sensor
 141 bits. (Hint: look for the 0/1and 1/0 crossings of the RC5 bi-phase data)  An
 142 actual raw RC5 code will span 2-3 DWORDS, depending on the actual alignment.
 143
 144 I'm pretty sure when no IR signal is present the receiver is always in a
 145 marking state(1); but stray light, etc can cause intermittent noise values
 146 as well.  Remember, this is a free running sample of the IR receiver state
 147 over time, so don't assume any sample starts at any particular place.
 148
 149 Additional info
 150 ~~~~~~~~~~~~~~~
 151
 152 This data sheet (google search) seems to have a lovely description of the
 153 RC5 basics:
 154 http://www.atmel.com/dyn/resources/prod_documents/doc2817.pdf
 155
 156 This document has more data:
 157 http://www.nenya.be/beor/electronics/rc5.htm
 158
 159 This document has a  how to decode a bi-phase data stream:
 160 http://www.ee.washington.edu/circuit_archive/text/ir_decode.txt
 161
 162 This document has still more info:
 163 http://www.xs4all.nl/~sbp/knowledge/ir/rc5.htm