Hi,
I'm trying to apply an Offset on the ADC, I'm using a H743. I'm pretty sure I have the ADC working correctly, because measuring temperatures (MCU internal and one external) as well as measuring some voltages on my board result in plausible values.
Now I have to read some currents, but I there is an offset of about -0.2A when the line is in idle. I have:
- Calibrated the ADC.
- Set the ADC to 12 bit.
- Left shift the result by 4 bit, back to an uint16.
- Wait until the reading is stable, this means that only the two LSB change for 100 ms.
Then I get the value from the JDR1 (I'm using injected conversions) and subtract 2^15-1 from that, since the expected value would be 1.25V and VDDA is 2.5V. I set the difference (which is negative) as the offset and apply that to the channel. But then my reading is too high. I've experimented a bit, and for now I right shift the difference by 2 bit and now I get a better reading, so that I at least can continue to work.
Has anyone a hint what I'm doing wrong?
Here my offset calculation (through a self made wrapper around the registers):
const auto rawValue = adc.injectedData1();
AdcOffset offset;
offset.Channel = Channel::Adc1::MotorPhaseA;
offset.Offset = rawValue - onePointTwoFiveInRaw;
offset.Offset >>= 2;
offset.Offset &= ~0b1111;
adc.setOffset(offset, /*number=*/0);
