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    clj-gpio

    Clojars

    Jan 5, 2016


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    The README below is fetched from the published project artifact. Some relative links may be broken.

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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 clojure.core.async.impl.channels.ManyToManyChannel@1197ad0>
    

    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.