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I had proposed using a Micro:bit to control a programmable current sink to implement an VI curve tracer for the November Project14 DIY Test Instrumentation competition.  Unfortunately, I had some personal issues that prevented me from being able to enter the competition.  To my surprise, I received one of the Micro:bit packages from Element14 while I was away.  Since I received the Micro:bit package, I thought that I would implement my design and post it here even though the competition is closed.  I also need to complete a roadtest, so it may take me a couple of weeks before I can complete this project.


Block diagram of the project:

Curve Tracer Block Diagram


Parts list:

1Waveshare 160x128 LCD Display
1MCP4725 I2C DAC Module
1GL358 OpAmp
12N2222A NPN Transistor
1Battery Holder
2AA Batteries
Various Resistors and Capacitors



The Waveshare LCD module with the Micro:bit attached.


Waveshare LCD Display


The challenges that I see with this project will be mainly in generating the code.  I'm new to the Micro:bit ecosystem so I'm not sure how much effort it will take to interface the I2C DAC and the SPI LCD Display.  If this were an Arduino (or equivalent - I use a lot of ESP8266s) it would be straightforward because of all the available libraries.  Waveshare provides code for running the LCD with the Microsoft MakeCode IDE but then I might have to "bit bang" the I2C so I'll probably use a different development environment.