linux/Documentation/bt8xxgpio.txt
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   1===============================================================
   2==  BT8XXGPIO driver                                         ==
   3==                                                           ==
   4==  A driver for a selfmade cheap BT8xx based PCI GPIO-card  ==
   5==                                                           ==
   6==  For advanced documentation, see                          ==
   7==  http://www.bu3sch.de/btgpio.php                          ==
   8===============================================================
   9
  10
  11A generic digital 24-port PCI GPIO card can be built out of an ordinary
  12Brooktree bt848, bt849, bt878 or bt879 based analog TV tuner card. The
  13Brooktree chip is used in old analog Hauppauge WinTV PCI cards. You can easily
  14find them used for low prices on the net.
  15
  16The bt8xx chip does have 24 digital GPIO ports.
  17These ports are accessible via 24 pins on the SMD chip package.
  18
  19
  20==============================================
  21==  How to physically access the GPIO pins  ==
  22==============================================
  23
  24The are several ways to access these pins. One might unsolder the whole chip
  25and put it on a custom PCI board, or one might only unsolder each individual
  26GPIO pin and solder that to some tiny wire. As the chip package really is tiny
  27there are some advanced soldering skills needed in any case.
  28
  29The physical pinouts are drawn in the following ASCII art.
  30The GPIO pins are marked with G00-G23
  31
  32                                           G G G G G G G G G G G G     G G G G G G
  33                                           0 0 0 0 0 0 0 0 0 0 1 1     1 1 1 1 1 1
  34                                           0 1 2 3 4 5 6 7 8 9 0 1     2 3 4 5 6 7
  35           | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
  36           ---------------------------------------------------------------------------
  37         --|                               ^                                     ^   |--
  38         --|                               pin 86                           pin 67   |--
  39         --|                                                                         |--
  40         --|                                                               pin 61 >  |-- G18
  41         --|                                                                         |-- G19
  42         --|                                                                         |-- G20
  43         --|                                                                         |-- G21
  44         --|                                                                         |-- G22
  45         --|                                                               pin 56 >  |-- G23
  46         --|                                                                         |--
  47         --|                           Brooktree 878/879                             |--
  48         --|                                                                         |--
  49         --|                                                                         |--
  50         --|                                                                         |--
  51         --|                                                                         |--
  52         --|                                                                         |--
  53         --|                                                                         |--
  54         --|                                                                         |--
  55         --|                                                                         |--
  56         --|                                                                         |--
  57         --|                                                                         |--
  58         --|                                                                         |--
  59         --|                                                                         |--
  60         --|                                                                         |--
  61         --|   O                                                                     |--
  62         --|                                                                         |--
  63           ---------------------------------------------------------------------------
  64           | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
  65           ^
  66           This is pin 1
  67
  68
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