cl-gpio

2017-05-16

About cl-gpio

This is a bindings library for the Linux GPIO kernel module as described on https://www.kernel.org/doc/Documentation/gpio/sysfs.txt. It provides both primitive access and more sophisticated constructs to work with interrupts and such.

How To

Enumerate a list of all available GPIO pins on your system:

(gpio:pins)

You can then access the direction, edge, and active-low of each pin:

(setf (gpio:direction 0) :out)
(gpio:active-low 0)

If you try to read or set a PIN's value, its direction is automatically adjusted as necessary:

(gpio:value 0)
(setf (gpio:value 0) T)

On SBCL you can also wait for values:

(progn (gpio:await-value 0)
       (format T "Whoah, 0's edge is ~a to ~:[0~;1~]" (edge 0) (value 0)))

Or even install handlers:

(defun pin-value-handler (pin value)
  (format T "~& ~a changed value to ~a." pin value))
(gpio:with-pin-handler (#'pin-value-handler 0 :falling)
  (format T "Waiting for a change on 0...")
  (loop (sleep 0.001)))

Naturally you'll have to refer to your particular board/system's specification to be able to tell which pins are supposed to be used for what. For the Raspberry Pi 2/3, it would be:

rpi23-pin-mapping

rpi23-pin-mapping

(Source)

Author
Nicolas Hafner <shinmera@tymoon.eu>
Maintainer
Nicolas Hafner <shinmera@tymoon.eu>
License
Artistic