The Raspberry Pi is a cheap and simple Linux compatible computer with high speed GPIO. Read all about it here.

The board has male GPIO header pins. The plus models and version 2 have 40 pins, the original models 26 pins.

                +---P1---+
3V3             01      02 5V
GPIO0/GPIO2     03 A/A+ 04 5V
GPIO1/GPIO3     05 B/B+ 06 GND
GPIO4           07      08 GPIO14/TX
GND             09      10 GPIO15/RX
GPIO17          11      12 GPIO18
GPIO21/GPIO27   13      14 GND
GPIO22          15      16 GPIO23
3V3             17      18 GPIO24
GPIO10          19      20 GND
GPIO9           21      22 GPIO25
GPIO11          23      24 GPIO8
GND             25______26 GPIO7
EEPROM ID_SD    27      28 EEPROM ID_SC
GPIO5           29 A+   30 GND
GPIO6           31 B+   32 GPIO12
GPIO13          33      34 GND
GPIO19          35      36 GPIO16
GPIO26          37      38 GPIO20
GND             39      40 GPIO21
                +--------+

Ribbon cables may be used to extend the GPIOs. In this instance a female presentation will be given.

For the older models, a 26-pin ribbon is needed, this is much like an old midi daughter-board cable.

  _________________________________________
 /                                        /
-----------------------------------------+
|  7  8 25 0V 24 23 0V 18 15 14 0V 5V 5V |
|                                        |
|                                        |
| 0V 11  9 10 3V 22 27 17 0V  4  3  2 3V |1
+-------------------__-------------------+

For PLUS and version 2 models an old style 40-pin IDE ribbon cable may be re-purposed as a GPIO extension.

  ______________________________________________________________
 /                                                             /
+-------------------------------------------------------------+
| 21 20 16 0V 12 0V SC  7  8 25 0V 24 23 0V 18 15 14 0V 5V 5V |
|                                                             |
|                                                             |
| 0V 26 19 13  6  5 SD 0V 11  9 10 3V 22 27 17 0V  4  3  2 3V |1
+-----------------------------___-----------------------------+

Velleman K8048 interface

The following connections refer to the R-PI GPIO header directly. Ensure that power is only ever applied from GPIO 3V3 on PIN 1 and never 5V.

Single common data I/O connection (RPI or GPIO bit-bang driver for R-PI & OpenWRT)

 R-PI                              PICMicro       GPIO header     .k8048
 ====                              ========       ===========     ======

 3V3-------------------------------VDD--+         PIN 1 (P1-01)
                                        |
 GND-------------------------------VSS  R1        PIN 6
                                        |
 GPIO04--------R3-470R-------------VPP--+         PIN 7           VPP=4

 GPIO25--------R4-470R-------------PGC            PIN 22          PGC=25

 GPIO24--------R5-470R-------------PGD            PIN 18          PGD=24

 GPIO22--------R6-470R-------------PGM--R2-+      PIN 15          PGM=22
                                           |
                                          ///
(R1) 10K !MCLR pull-up
(R2) 10K where appropriate (PGM is not present on all devices).
(R3..R6) 470R.

p16 lvp id
[000000] [PROGRAM]    10000 WORDS
[01FFF8] [CONFIG1]     F7BA
[01FFFA] [CONFIG2]     FA10
[01FFFC] [CONFIG3]     F8F1
[01FFFE] [CONFIG4]     F980
[3FFFFE] [DEVICEID]    5A61 DEV:5A60 (5A:3) REV:1 PIC18LF27J53

p14 id
[0000] [PROGRAM]  2000 WORDS
[2000] [USERID0]  0001 .
[2001] [USERID1]  0002 .
[2002] [USERID2]  0003 .
[2003] [USERID3]  0004 .
[2004] [RESERVED] 3FFF .
[2005] [RESERVED] 3FFF .
[2006] [DEVICEID] 2062 DEV:2060 (103) REV:2 PIC16F886
[2007] [CONFIG1]  30E2
[2008] [CONFIG2]  3EFF
[2009] [CALIB]    2278
[2100] [DATA]     0100 BYTES

p14 program pic16f886.hex
Total: 732
p14 verify pic16f886.hex
Total: 732 Fail: 0

RPi GPIO
Void Linux for Raspberry Pi