Some Adc channels always returning 0

[AnthonyPinard]

Hello all, 

I am using S32K312, RTD 2.0.3 and Tresos 29.0.0

I have a problem with the ADC module. Currently, Adc0 is SW triggered and Adc1 is triggered by the BCTU. Everything works great except for a small detail.... two channels of the Adc0 instance are always returning 0.

Six of the eight channels are returning perfectly coherent values while channels S8 and S9 always read 0 when there is in fact a voltage applied on their pin. (confirmed with scope) The NCMR1 register reads 0x0000_047B, which means the concerned channels are supposed to be converted. The 8 channels are in the same group, and they are all configured the same way. The pins are all configured as the right Adc channel.

I tried triggering Adc0 by Hw and with the BCTU, but it did not help my cause. I also tried shutting off Adc1 to see if it was interrupting Adc0. Finally, I tried triggering only the two problematic channels but, they still read 0.

Any idea what could be causing this issue? 

Thanks,

[Robin_Shen · Accepted solution]

Hi

Which two pins do you connect the analog signals of ADC0 S8 and S9 to? There is a bug in RTD 2.0.x that may cause this problem. Please see the discussion here: S32K312 - ADC Problem

Best Regards,
Robin
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[AnthonyPinard]

Hi Robin, 

The two channels are PTA0 and PTA1. However, I noticed that the channels are triggering on pins PTB13 and PTB14, which are configured as GPIOs. 

Is it because ADC0_S8 and ADC0_S9 are supposed to be only available through the port B and not port A?

Thanks

[Robin_Shen]

No. This may caused by the bug of RTD: https://community.nxp.com/t5/S32K/S32K344-ADC-HAS-ADC-INTERLEAVE-problem/m-p/1548855