Hardware Hacks

We have built various bits and pieces to enable easier use of our hardware. Some of these are documented here in case others might find them useful. The issue is that we want our embedded hardware to be shareable between multiple users and an automated test harness. The manufacturers of most of our gadgets assume we’re going to be using a TTL to USB serial converter and Fastboot; this doesn’t scale, as when you have several plugged in, the enumeration order is not fixed, so there’s no way to tell which of many gadgets you are talking to.

The general approach we take is:

  1. As far as possible, boot everything on power-up via DHCP and TFTP
  2. Connect a debug serial port via a LevelConverter to a Lantronix serial concentrator. An ETS16P for example provides 16 RS422/RS232 ports, and can be obtained for less than $100 on eBay.
  3. Connect power for each device via a network-controllable switch. For most of our gadgets we’re using a cubieTruck and an pair of arduino-connected 8-way relay boards, hooked up to an old AT power supply top give 5V or 12V depending on each board’s requirements. It doesn’t matter much provided that via the network, one can turn on, turn off, and query the power state of a particular port.

We use a set of MachineQueue scripts to arbitrate access to the various gadgets.

A few machines already have a base-management-controller; if they have it we use it.

One machine, the CMA34D, needed some extras; they are documented on CMA34DBMC.