The Industrial Raspberry Pi Forum

Hello,

From the documentation it appears that the ADC in the AIO card is capable of 16 bit resolution but the software seems to limit the resolution to 16 bits. We have an application where we would like to use the AIO card to read mv/V signals directly at 24 bit resolution with a sampling rate of 25hz. Is this achievable?

Not right now I'm afraid. The 24-bit value is truncated to a 16-bit value by the AIO firmware and sent over the PiBridge to the Core/Connect, which just copies it into the process image. We'd have to extend the AIO firmware and the protocol used to communicate with the AIO to allow access to higher resolution values. We can put that on our todo list but it may take a while until we get around to imlement that. So right now your best bet is to use the multiplier/divisor/offset to scale the value to your needs and squeeze as much entropy as possible out of the 16 bits.

FWIW, the upcoming RevPi Compact has an MCP3550-50 ADC which has a 21-bit resolution (plus some over/underrange), but it requires about 83 ms per readout in addition to 40 ms settling time of the mux behind which it's located, so the maximum you'll get is 8 Hz.