peterschwarz / Clj Gpio
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clj-gpio
A basic library for reading, writing and watching GPIO signals on a Raspberry Pi, in a Clojure REPL-friendly way. Now, also targets ClojureScript.
Usage
Add the following to your project.clj
[clj-gpio 0.2.0]
Fire up a REPL, and require gpio.core.
GPIO Read/Write
We can open a basic read/write gpio port as follows (let's say we have an LED conncted to GPIO 17):
user=> (require '[gpio.core :refer :all] :reload)
nil
user=> (def port (open-port 17))
#'user/port
To read the value of the port, we can do the following:
user=> (read-value port)
:low
To set values on the port, The port needs to be configured for out mode:
user=> (set-direction! port :out)
This also works with 'out and "out". A value can be written to the port
as follows:
user=> (write-value! port :high)
With our LED connected to gpio 17, we should see it turned on. We can also
read back the value and see that (= :high @port).
We can also toggle the state, for convenience:
user=> (toggle! port)
which will flip the state from :low to :high or vice versa.
GPIO Listening.
We can also pull events off of a gpio port by using open-channel-port. In
addition to setting directions, values etc, we set the edge change that we'll
listen for, and we can create a core.async channel from which can receive
values.
For example (if we have a push button on GPIO 18):
user=> (def ch-port (open-channel-port 18))
#'user/ch-port
user=> (set-direction! ch-port :in)
...
user=> (set-edge! ch-port :both) ; or :falling, :rising, and :none to disable
...
We'll also set the bit to :high when the button pressed:
user=> (set-active-low! ch-port true)
Let's turn on the LED we defined in the Read/Write example above when our button is pressed:
user=> (def ch (create-edge-channel ch-port))
#'user/ch
user=> (require '[clojure.core.async :as a :refer [go <!]])
nil
user=> (go (loop []
(when-let [value (<! ch)]
(write-value! port value)
(recur))))
#<ManyToManyChannel [email protected]>
When we're finished with the channel, we call:
user=> (a/close! ch)
nil
And clean up our ports:
user=> (close! port)
nil
user=> (close! ch-port)
nil
Development
First compile the java sources:
lein javac
then fire up your REPL and require gpio.core as usual.
Note, the edge channel will only operate on the Raspberry PI platform.
License
Copyright © 2014 Peter Schwarz
Distributed under the Eclipse Public License, the same as Clojure.