System Overview

Arduinos

Newer version of Arduinos, in particular the Arduino Yun can provide much of the functionality of Raspberry Pis, but also have some advantages including being able to be powered over PoE. The Yun also has a linux side, meaning it can run pynedm scripts.

Field Switch device

This is a device used to handle switching of fields in the internal_coils system.

A backup of the SD card for this device is available in two places: (Cluster server ) (Osthalle server).

Note that in this image, the username/password for the pynedm daemon have been scrubbed. To flash this image to a new card one must use dd, e.g.:

gunzip -c arduino.img.gz | sudo dd of=/dev/sd_card

where the SD card must be at least 4 GB large.

The code on the Arduino Yun runs a simple sketch as well as a pynedm daemon which is started using an init.d script. Please see the image and code for more details.

Note, that you must enable extroot on a new Arduino Yun device to have this work. (When doing this, be careful not to format the SD card again!) See here and here for more information.

A couple more points regarding the Yun:

• If the Yun fails to mount the SD card in the /overlay directory and instead mounts it in, /tmp/overlay-disabled, this is because the md5sum doesn’t math. (This will probably be the case.) Using the SD card flashed from this version will likely require copying the md5sum, e.g.:

cp /.extroot.md5sum /tmp/overlay-disabled/etc/extroot.md5sum

See here for more details.

• The resolution of the name server seems not always to work. For this reason, try converting IP names to IP addresses.
• Dealing with the Arduino Yun takes some knowledge about how OpenWrt works and will also require decent linux knowledge to debug issues. (These will happen, the Arduino Yun system is not a particularly out-of-the-box-ready system for users who don’t have much experience with such devices.)

Code