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A simple library for serial port communication with Clojure. Although serial communciation may be considered old tech, it's useful for a communicating with a plethora of devices including exciting new hardware such as the Monome and the Arduino.
serial-port has the following dependencies:
The easiest way to to install
serial-port is requiring the serial-port clojar in your
project.clj and using cake to pull the dependencies. Cake has great support for native dependencies and the serial-port clojar depends on the rxtx22 clojar which packages the RxTx native libraries.
All this means you simply need to add
serial-port to your list of dependencies in your
(defproject your-project "0.1.5" :description "Your fabulous project that uses a serial connection" :dependencies [[org.clojure/clojure "1.3.0"] [serial-port "1.1.0"]])
1.1.0 is replaced with the version you wish to use.)
cake deps and cake will pull the correct dependencies (both native libs and jars) and put them in the right place for you to use with
cake repl or
Using the library
Just make sure you pull in the
serial-port namespace using something like:
Finding your port identifier
In order to connect to your serial device you need to know the path of the file it presents itself on.
serial-port provides a simple function to list these paths out:
=> (list-ports) 0 : /dev/tty.usbmodemfa141 1 : /dev/cu.usbmodemfa141 2 : /dev/tty.Bluetooth-PDA-Sync 3 : /dev/cu.Bluetooth-PDA-Sync 4 : /dev/tty.Bluetooth-Modem 5 : /dev/cu.Bluetooth-Modem
In this case, we have an Arduino connected to
Problem on Ubuntu Linux
From ubuntu linux 11.04 and forward, you may not see your device.
The RXTX library searches for serial ports with the
/dev/ttySxx naming convention.
Your device may be called
/dev/ttyACM0 and so is not found.
From the repl point of view, you could make your system aware of it:
(System/setProperty "gnu.io.rxtx.SerialPorts" "/dev/ttyACM0")
From the OS point of view: You could create a symbolic link with a name that satisfies this, so for example:
sudo ln -s /dev/ttyACM0 /dev/ttyS42
Connecting with a port identifier
When you know the path to the serial port, connecting is just as simple as:
However, you'll want to bind the result so you can use it later:
(def port (open "/dev/tty.usbmodemfa141"))
The simplest way to read bytes from the connection is to use
on-byte. This allows you to register a handler fn which will be called for each byte received. So, to print out each byte just do the following:
(on-byte port #(println %))
It's also possible to register a handler for every n bytes. The monome communicates by sending pairs of bytes, one byte to describe whether a button was pressed or released, and another to describe the coordinates of the button. You can register a handler to receive pairs of bytes as follows:
(on-n-bytes port 2 (fn [[action coords]] ...))
If you wish to get raw access to the
InputStream this is possible with the function
listen. This allows you to specify a handler that will get called every time there is data available on the port and will pass your handler the
InputStream to allow you to directly
.read bytes from it. Both
on-n-bytes generate such handlers acting as a proxy between your specified handler and the incoming data events.
When the handler is first registered, the bytes that have been buffered on the serial port are dropped by default. This can be changed by passing false to
listen as an optional last argument.
Only one listener may be registered at a time. If you want to fork the incoming datastream to a series of streams, you might want to consider using lamina. You can then register a handler which simply enqueues the incoming serial data to a lamina channel which you may then fork and map according to your whim.
Finally, you may remove your listener with
The simplest way to write bytes is by passing a byte array to
(write port my-byte-array)
There are a couple of convenience functions available if you're dealing with plain Integers.
write-int allows you to write a simple integer to the serial port and
write-int-seq allows you to pass a sequence of integers which are then converted to a byte array which is subsequently written to the serial port:
(write-int port 20) (write-int-seq port [20 10 2 100])
Closing the port
Simply use the
- Sam Aaron
- Jeff Rose
Copyright (C) 2011 Sam Aaron
Distributed under the Eclipse Public License, the same as Clojure.