>Psychtoolbox>PsychDemos

RaspberryPiGPIODemo - Show basic use of GPIO’s on RaspberryPi.

Demos full access to the Pi GPIOs.

Accessing the GPIOs as non-root requires the user account
to be a member of the Unix group ‘gpio’. PsychLinuxConfiguration
should take care of adding your account if you let it do that
setup for you. The ‘gpio’ command line utility allows to configure
aspects of the GPIOs which your code can’t control as non-root,
therefore you’ll see multiple system() callouts in this script
to that helper utility. If the RPiGPIOMex mex file doesn’t work
then you will need to install the ‘wiringPi’ package to provide
the required libwiringPi runtime library. On RaspberryPi OS 11 and
later, wiringPi does not exist anymore, but you may be able to find
an alternative Debian (armhf) package from the following link:

https://github.com/WiringPi/WiringPi/releases

The demo shows digital i/o by flashing/alternating the two
LEDs on the RPi 2B, Red power, and green status.

It shows how to efficiently wait for a rising edge
trigger on Broadcom pin 17, a real GPIO pin on the
connector. To avoid the need to actually connect
a switch to the connector, uses internal programmable
pullup and pulldown resistors to simulate external
trigger input to the pin.

Please note that the RPiGPIOMex file is just meant as
a temporary stop-gap solution to get things going, until
PTB gains a universal I/O driver. Development and support
of RPiGPIOMex may cease at a future point in time, it may
even get removed from the distro! Plan accordingly, maybe
use a M-File wrapper around it to simplify transition to a
future better I/O driver.

All pin numbers used with RPiGPIOMex are Broadcom GPIO pin
numbers, not pin numbers on the connector or wiringPi pin numbers!

A nice translation table between connector pins and Broadcom GPIO
pins can be found on the following website: https://pinout.xyz
The command ‘pinout’ in a terminal will also print the pin mapping.