EEZ Bench Box 3

Modular, open-source test & measurement chassis

Dec 19, 2019

MicroPython Arrives on BB3

by Denis Kotlar (a.k.a. prasimix)

After much preparation and an initial proof-of-concept carried out a few months ago, we now have a functional implementation of MicroPython running on the STM32F7 MCU at the heart of BB3. Achieving this required that we modify EEZ Studio to simplify the import of MicroPython scripts and to facilitate the transfer of those scripts between your PC and your BB3. Once transferred, MicroPython scripts can be used repeatedly on the BB3 without requiring access to a PC.

MicroPython support opens up completely new possibilities for automating every day test and measurement work that requires access to a programmable power supply.

MicroPython, also know as Python for microcontrollers, is a software implementation of a programming language, largely compatible with Python 3, that is written in C and optimized to run on microcontrollers. It has become quite popular thanks to its simplicity, its code readability, its quick learning curve, and the fact that it does not require any special compilation. These qualities make it a perfect candidate for automating test and measurement procedures.

Our first demonstration of BB3’s MicroPython scripting is a simple diode tester that can be used to determine the breakdown voltage of a diode, such as a Zener diode or TVS, that is normally inversely biased. You can specify a name for the diode, via the TFT touchscreen, and it will be used to name a file on the SD card. BB3 will store the data it measures within that file. You can also set a custom voltage step, rather than using the default 100 mV, if test speed is more important than precision.

The script will use one or two DCP405 modules in the first two slots. As a result, the test voltage could be up to 80 V (with two modules coupled in series). The test current is set to 10 mA to limit max. power dissipation. When the breakdown voltage is found (i.e. when all 10 mA is drawn), script execution is stopped, and the results are displayed. Your measurements can be transferred to your PC with a single click. EEZ Studio now includes a Save as CSV option that allows you to process results using a spreadsheet application or other external software.

The diode-tester.py example script will be included in each BB3 we ship. And more scripts are on the way. Examples might include a curve tracer, an electrolytic capacitor reformer, an automated diode tester, a battery charger, and a simple function generator. Your suggestions are welcome!

Thanks for your support, Denis


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