I've previously covered running LAVA on ARM devices, now that the packages are in Debian. I've also covered setting up the home lab, including the difficulty in obtaining the PDU and relying on another machine to provide USB serial converters with inherent problems of needing power to keep the same devices assigned to the same ser2net ports.

There have been ideas about how to improve the situation. Conferences are a prime example - setting up a demo involving LAVA means bringing a range of equipment, separate power bricks, separate network switches (with power bricks), a device of some kind to connect up the USB serial converters (and power brick) and then the LAVA server (with SATA drive and power brick) - that is without the actual devices and their cables and power. Each of those power cables tend to be a metre long, with networking and serial, it quickly becomes a cable spaghetti.

Ideas around this also have application inside larger deployments, so the hardware would need to daisy-chain to provide services to a rack full of test devices.

The objective is a single case providing network, power and serial connectivity to a number of test devices over a single power input and network uplink. Naturally, with a strong free software and open development bias, the unit will be Open Hardware running Debian, albeit with a custom Beaglebone Linux kernel. It's a Test Automation Controller, so we're using the name OpenTAC (Open Hardware Test Automation Controller).


Open hardware ARM device running Debian to automate tests on 4 to 8 devices, initially aimed at LAVA support for Linaro engineers. Power distribution, serial console, network and optional GPIO extensions.

The design involves:

  • A Beaglebone Black (revC)
    • USB hotplug support required, certainly during development.
  • Custom PCB connected as a Beaglebone Cape, designed by Andy Simpkins.
  • Base board provides 4 channels:
    • 5V Power - delivered over USB
    • Ethernet - standard Cat5, no LEDs
    • Serial connectivity
      • RS232
      • UART
    • GPIO
  • Internal gigabit network switch
  • Space for a board like a CubieTruck (with SATA drive) to act as LAVA server
  • Daughter board:
    • Same basic design as the base board, providing another 4 channels, equivalent to the base channels. When the daughter board is fitted, a second network switch would be added instead of the CubieTruck.
  • Power consumption measurement per channel
  • queries made via the Beaglebone Black over arbitrary time periods, including during the test itself.
  • The GPIO lines can be used to work around issues with development boards under test, including closing connections which may be required to get a device to reboot automatically, without manual intervention.
  • Serial connections to test devices can be isolated during device power-cycles - this allows for devices which pull power over the serial connection. (These are typically hardware design issues but the devices still need to be tested until the boards can be modified or replaced.)
  • Thermal control, individual fan control via the Beaglebone Black.
  • 1U case - rackable or used alone on the desk of developers.
  • Software design:
    • lavapdu backend module for PDU control (opentac.py) & opentac daemon on the BBB
      • telnet opentac-01 3225
    • ser2net for serial console control
      • telnet opentac-01 4000

The initial schematics are now complete and undergoing design review. A lot of work remains ...