Raspberry Pi GPIO port to IDC26/DB-25 ribbon cable

Using a IDC26/DB-25 ribbon cable with the GPIO of a Raspberry Pi is quite useful. It fits perfect on the GPIO port. But there are 2 drawbacks:

  • GPIO7 is not connected because DB-25 port has only 25 pins and Raspberry Pi’s GPIO port has 26.
  • The pinout numbers on the DB-25 side does not match the pinout numbers in the GPIO side.

Raspberry Pi IDC26 DB-25

TL;DR: This is the pinout in the DB-25 side if you use a IDC26/DB-25 ribbon cable:


In case you want to know why look first at the pinout of the Raspberry Pi’s GPIO:


And now the pinout correspondence on both DB-25 and IDC26 side of the ribbon cable:

DB-25 IDC26

As you can see the pin 2 in the GPIO port corresponds to the pin 14 in the DB-25 port, etc. This are the functions of every pin in the DB-25 port if you use a IDC26/DB-25 ribbon cable with your Raspberry Pi:

  1. 3.3V
  2. GPIO2 (I2C)
  3. GPIO3 (I2C)
  4. GPIO4
  5. GND
  6. GPIO17
  7. GPIO27
  8. GPIO22
  9. 3.3V
  10. GPIO10 (SPI)
  11. GPIO9 (SPI)
  12. GPIO11 (SPI)
  13. GND
  14. 5V
  15. 5V
  16. GND
  17. GPIO14 (UART)
  18. GPIO15 (UART)
  19. GPIO18 (PWM)
  20. GND
  21. GPIO23
  22. GPIO24
  23. GND
  24. GPIO25
  25. GPIO8 (SPI)

Raspberry Pi GPIO image by raspberrypi.org

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