STM32L452RE ADC Bad value on just one of the 9 channels

[JHong.1]

I have STM32L452RET6P running at 1.8V, 24MHz.

I am using nine ADC1 channels and am getting a very low value (about half) on ADC1-1 (PC0).

All inputs are set up the same way, with an RC filter (33kOhm/0.1uF). The sampling rate cycle is 12.5 at 10bits, sIngle-ended.

During debug, the values come out correct when I query each channel individually. ADC1-1 value is incorrect only during continuous query.

Would this be related to the max R_ain value? I understand that at this sampling cycle at 10 bits, the 33kOhm is over the max R_ain value. What I don't understand is that the bad value only comes out of ADC1-1 during continuous mode.

If not related to R_ain, what could be causing this issue?

Thank you.

[waclawek.jan]

Is this the first channel in the sequence, samples after a longer delay? If yes, add a read to some arbitrary channel before this one into the sequence, and read the errata.

JW

[JHong.1]

JW,

Thank you for your response.

When you say the first in the sequence, do you mean the ranking of the sweep through the ADC channels? Or do you mean the actual channel (I ask because the channel which has the issue is ADC Channel 1)?

[waclawek.jan]

Have you read the errata?

Wrong ADC result if conversion done late after calibration or previous conversion

That would imply that if you convert sequences more than 1ms apart, I am talking about the first in the sequence, i.e. the one set in ADC_SQR1.SQ1.

Please stick to terminology used in the Reference Manual, there is no "ranking" nor "sweep" used in the ADC chapter.

JW