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S32K ADC HW averaging issue

Question asked by Adria Perez on May 20, 2020
Latest reply on May 22, 2020 by Daniel Martynek

Hello,

 

MCU: S32K146

SDK: S32SDK_S32K1xx_RTM_3.0.0

RTOS: FreeRTOS

 

With the next ADC configuration:

- Clock: 8 MHz

- Number of ticks per sample: 12

- Trigger: by PDB

- HW averaging: enabled

- Number of samples per average: 32 (max)

I am facing an issue, which is getting an offset of 30 (digital) when performing a conversion, no matter whether it is in open load or there is a load present. I know those conversion results have an offset because when I perform conversions with HW averaging disabled, then I get in all cases values minus 30 (compared to conversions with HW averaging enabled).

If I increase the number of ticks per samples from 12 to 255 and enable HW averaging, then this offset of 30 disappears.

 

Note: I am always calibrating at the beginning ADC_DRV_AutoCalibration().

 

Can anybody please help me understand and solve this issue?

 

Best regards,

 

Adria

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