Testing this unit for few ours now, it seems that low range readings are not right. Instead of showing 0,01A, it’s showing double value, 0,02A… Again, having device that draws more than 0,1A makes it completely reliable and precise. I finally opened it to see how to pull ttl out of it, and it’s definitely not worth time and effort. Serial controller is based on Mega88, I don’t know anything about this chip. and board is high density smd, not very suitable for further modifications.
Edit: now I used multimeter, low end readings are ok, just ps I’ve used for testing is not performing well. So if you want passive display for your up to 20 Amps applications, 021 is way to go.