topic Re: ADC value differences. in S32K

ADC value differences.

daemangpark — Fri, 22 Jun 2018 01:36:11 GMT

Hi.
I use S32K144EVB. I think there are some differences between the input voltage and the value read by adc channel.
Test has been done under condition below.

SW : ADC_s32k144 (S32K example code)
HW : S32K144EVB

IDE : S32K design studio for ARM version 2018 R1.

1.Connect power from power supply to adc pin
2.Read caluated adc value.

results are as below.
(Input / caled value)
1.001V / 1018
1.101V /1125
1.201V /1224
1.5V /1531
2.001V /2047
2.501V /2561
3.001V /3075
3.501V /3594
4.001V /4103
4.500V /4626
4.800V /4925
5.000V /5000

The difference is growing when the input voltage goes to 5V.
I got 3 evb boards. and those gaps exist from All boards with the same SW (example codes).
Please check this out.#

Re: ADC value differences.

danielmartynek — Fri, 22 Jun 2018 11:00:53 GMT

Hi,

Have you calibrated the ADC module?

Please refer to Section 42.5.6 Calibration function, S32K1xx_RM_rev7

Regards,

Daniel

Re: ADC value differences.

daemangpark — Fri, 29 Jun 2018 05:05:55 GMT

Thanks Daniel.

It much better doing after calibration. But the differences are still. ( 10~20 mA level).

Do you think it is working well? Is it okay with these result? 10~20mA gap is acceptable? or any jobs are needed more?

Calibration has been done with API named ' void ADC_DRV_AutoCalibration(const uint32_t instance) '

The results are....

Input	ADC value	Calculated	Diff
1001	817	997	4
1501	1226	1496	5
2001	1635	1996	5
2501	2041	2492	9
3001	2451	2992	9
3501	2855	3485	16
4001	3265	3986	15
4500	3672	4483	17
4800	3918	4783	17
5000	4095	4980	20

Please give your opinion.

BR.

Daemang Park.