I worked on 2 parts : the Arduino code and the integration in my desktop.

The arduino part was easy, I just had to read the serial port and wait for on of the 3 control characters I picked and set the corresponding pin to LOW.

But I met some difficulties with the serial port access from my PC. Initially I though I could avoid writing any "real" code and stick to Bash, I couldn't avoid some python script:

• I tried to send commands to the Arduino with picocom : OK
• I set up the serial port with stty and tried to echo/cat some commands to the serial port /dev/ttyX : failed
• I connected to the Arduino with socat - /dev/ttyUSB0 : OK
• I tried to send commands to the Arduino with echo -n s | socat - /dev/ttyUSB0 : failed

Then I searched the internet and found a page mentionning that to connect to the Arduino, you needed a 3 seconds delay for it to be ready to receive serial data. I had never heard of this "reset on serial connection behaviour" but it seemed to match what I was observing, so I tried the following command :

• echo $(sleep 3 && echo s)| socat - /dev/ttyUSB0 :ok

It worked, but it is not really usable, I don't want to have a 3 seconds delay for every command I send.

So instead I tried to use a pipe or UDP socket :

• socat PIPE:/var/run/pipo.pipe /dev/ttyUSB0,raw :failed
• socat UDP-LISTEN:6666,fork GOPEN:/dev/ttyUSB0 : failed

So I wrote a small python script that listens to UDP packets and send them on the serial port. This will make it easier to run on Windows

As I am using Awesome, I created some shortcuts to control the treadmill by adding the following in /etc/xdg/awesome/rc.lua :

awful.key({ modkey, "Control" }, "Left", function() awful.util.spawn("/usr/local/bin/treadmill-control m") end),
awful.key({ modkey , "Control"}, "Up", function() awful.util.spawn("/usr/local/bin/treadmill-control s") end),
awful.key({ modkey , "Control"}, "Right", function() awful.util.spawn("/usr/local/bin/treadmill-control p") end),

treadmill-control is just a very basic script that sends the first parameter on a UDP socket :

#! /bin/sh

if [ $# -ne 1 ] ; then
echo "error $0 needs a single parameter :"
echo "s : start/stop the trheadmill"
echo "p : increase speed"
echo "m : decrease speed"
fi

echo -n $1 | socat - UDP:127.0.0.1:5005