Hi,
I was thinking of designing a simple FOC capable board, just a tad bigger than the simplefocmini. The main thing I was adding was the low side current sense capability… And then I saw in the RP2040 docs that this is impossible due to something with the ADC…
But it isn’t explained WHAT the problem is. So is the current implementation lacking in some way and support is expected in a couple of weeks even before I could have my hardware ready or is it something fundamental?
I don’t really know anything about the RP2040 hardware, but this page says “Raspberry Pi Pico’s ADC features are not sufficient for low-side current sensing” which sounds fundamental. You need to be able to trigger the ADC to read at a certain point in the PWM cycle for lowside.
Inline sensors can be read at any time. My favorite for its small size and simplicity is ACS711KEXLT. The reading is very noisy, but you can take a bunch of samples and average them to smooth it out. From my testing, 32 samples over a 30 microsecond period gets it down to about ±22mA variation with the 15.5A version.
INA240 can be used with inline shunts and gives better accuracy, but takes up more board space and is a bit more expensive.