An adapter for the BM867/9 multimeter, acting as COM port. The original cable costs 50 euros; this costs less than one fifth and does more.Designed by embedblog in Czechia
A very useful feature of any multimeter is the ability to output its measurements to a computer, because then, with simple scripts, you can automate many measurements. The BM867s/869s is a great mu...Read More…
A very useful feature of any multimeter is the ability to output its measurements to a computer, because then, with simple scripts, you can automate many measurements. The BM867s/869s is a great multimeter, the only pity is that the USB adapter is sold separately and costs 50 euros (60 USD), which is just ridiculous.
So I made this adapter. It communicates with the computer via a CH330 (USB-serial chip), so it acts as a serial port. The brain is an ATtiny45, which decodes the output to a human readable form - the original cable does not even do that! So all you need is a serial terminal of your choice, you are not stuck with the proprietary firmware from Brymen (this, for example, allows you to really easily input data into MS Excel). And if you want to read the data into a program of your own, all you need to use is the scanf function (which is much much simpler then decoding the raw output - the tiny45 already did the hard work for you!).
On power up, it starts in the default mode, that is, it reports once per second. You can then send it the following commands: - "F": it reports data at full speed, roughly 5 times a second - "O": it reports data roughly once per second - "S": it stops reporting automatically - "D": it sends a single report (in stop mode) - "R": toggles between raw data and decoded output
Here you can see it in action:
The case is 3D printed from PLA and put together with two M2 screws. You can either order it as an optional extra or print it yourself. But note that the case needs tight tolerances, so you might need to adjust it according to your printer.
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Czech Post: Air mail (+ tracking)
Shane | Feb. 22, 2020
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