Test Hardware

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Here is information about hardware that is useful for testing embedded Linux systems. This page is intended to be a collecting point for hardware that people have found useful in their own testing, or in board farms.

Test Configurations

A "device under test" (DUT) is the hardware to be tested. This is usually a development board, when the product is under development, but it can be a finished product as well. There are a large variety of ways to connect with, control and communicate with the DUT.

Here are some sample configurations that are common:

simple connection to host, with local peripherals

In the simplest case, a "device under test" (DUT) will be connected directly to a host machine, with a network connection to the host, and local USB keyboard and/or mouse, and some display output (usually microHDMI).

This allows for testing and debugging the board using network tools (usually scp and ssh) to copy files to and from the target, and to execute commands on the target.

This simple configuration does not provide for serial console support.

== connection to host, with serial console This consists of:

* network connection to host
* serial console connection to host:
  * often provided by serial port on DUT with serial-to-USB cable connecting to USB on the host device
  * sometimes (increasingly) the DUT has an on-board serial-to-USB chip. So the DUT provides a micro-USB connection, and all that is required by the user is a standard micro-USB cable.

power control

For some tests, or to recover from some testing failures (ie machine hang) it is important to be able to power-cycle the DUT. A third level of complexity is to support power control for a board. The easiest way to do this is with an network-controlled power switch. This allows turning the A/C power off and on at the wall-wart, for development boards or devices that are powered from a mains circuit.

For battery-powered or USB-powered devices, it may be more complicated. Many boards provide a reboot or reset capability with buttons on the board. Some phones require complex button combinations, holds or sequences to reboot the device. For these, it is necessary to use switch control hardware. You can use hook pins to short-circuit the button connections, or re-wire the electrical connections on a power supply or board, to allow for relay or switch control of power to the board.

Additional hardware connections

Additional hardware connections to the DUT may be accessed, monitored, or controlled during a test. For example, for USB testing it may be useful to automatically connect and disconnect USB buses. This can be done with specialized hardware, or with broken-out wiring control of certain signal or power lines in a cable. Another example is simulating inserting or removing removable media by controlling certain lines in the bus to the peripheral connectors for a device.

Test hardware

Power control

Here are some devices that are handy for controlling power to DUTs

Console access

  • USB to serial converters

Switch control/Relays

  • Target Switch Control From Parallel Port - circuit schematics for building your own opto-isolated switches controlled by host parallel port
    • This was more useful when most desktop machines had parallel ports as standard hardware

Bus/connector control

Network access

Most boards connect to the test network or the Internet via standard networking cables and protocols (ethernet, 802.11 wifi, etc.)

USB control/switching

  • Sony Debug Assist board - this board allows connecting and disconnecting USB, as well as switching between multiple USB inputs
    • For example, it allows you to have a USB charger, a connection to a USB host, and a USB gadget connection, and switch between them.

USB hubs

Small USB hubs (4-port or 7-port) are quite common and inexpensive.

When building a board farm, it is common to need multi-port hubs.

  • Anyone have a recommendation?

Multi-function control boards

* USB control and switching
* power control, including voltage and amperage control
* power measurement
* switch control - controls up to 3 switches on the DUT
* serial console - has a serial-to-USB feature, with auto-voltage leveling

Presentations