USB Tester on 200mA scale
William Garrido from Fried Circuits launched a really nice low power meter platform back in 2013, and I lent a hand in the design of the firmware. Very happy with the results, and we are only getting started!

This USB tester is primarily a breakout board for USB cables, so that it is possible to measure voltage and current on the power lines. All USB pins are broken out. I had designed a similar board when debugging tricky USB extender cable issues when I worked on the Paris BMW Showroom light installation back in 2011 – the “vortices of light” around the cars – , but had never though of turning it into an actual product: congrats to William for thinking of doing it, this is a really useful piece of kit!

William improved things further by designing an “OLED Backpack” that turns the tester into an autonomous instrument. The firmware of that backpack was initially fairly simple, and I contributed a series of improvements:

The latter feature set being especially nice: it turns the OLED backpack into a full blown power logger.


Power measurement breakout

Assembled VA Tester

Assembled VA Tester

This option on the tester lets you measure current and voltage on any power line, not only USB: easy, and useful!



Version 2.0 of the tester and backpack

Good charger

Good charger

Then William introduced version 2.0 of the tester:

  • Micro USB plug instead of mini USB: most welcome, as Mini USB is on its way out
  • A larger screen for the OLED Backpack

I took the opportunity to improve things further with that release, and designed a simple but fairly feature-complete serial interface in the firmware:

With this release, the OLED backpack is able to do pretty advanced power logging, as shown below:

Current on a Nexus 7

Current on a Nexus 7

Read the article above for a more in-depth explanation of the how to read the graph!


What is next?

Development on the tester has not stopped, neither on the firmware nor on the hardware, so stay tuned for more news soon!