TMS570LC4357: Hercules_ADC_Calibration

Vijay Wankhede

Part Number: TMS570LC4357
Other Parts Discussed in Thread: HALCOGEN

Tool/software:

I'm working with the TI Hercules TMS570LC4357 Development Kit and trying to calibrate ADC. I have used adcCalibration function but not getting expected results. I have checked Vref it's 3.09V and ADC is 12 bit configured.
Please refer below test results for your reference.

ADC without Calibration

Input	Expected ADC count	Actual Input	Actual ADC count
0	0	61mv	30
1	1365	1.01	1330
1.5	2047.5	1.51	2006
2	2730	2.06	2756
2.5	3412.5	2.5082	3355
3	4095	3.03	3882

ADC with Calibration

Input	Expected ADC count	Actual Input	Actual ADC count
0	0	61mv	0
1	1365	1.01	672
1.5	2047.5	1.5	1331
2	2730	2	2017
2.5	3412.5	2.51	2700
3	4095	3	3218

8 months ago

0 jagadish gundavarapu 8 months ago

TI__Guru* 75096 points

Hi Vijay,

Can you please refer below thread once:

(+) TMS570LC4357: Internal temperature measure - Arm-based microcontrollers forum - Arm-based microcontrollers - TI E2E support forums

I am suspecting same root cause of this issue as well.

--
Thanks & regards,
Jagadish.

0 Vijay Wankhede 8 months ago in reply to jagadish gundavarapu

Prodigy 90 points

Hi Jagadish,

Thanks for you'r response. I have connected J8 jumper to get 3V as Vref and Im working with respect to 3V reference only but even though at 3V I should get 4095 ADC count you can refer my test results above. Point is I'm not getting calibrated results even after use of adcCalibration() (generated by HALCoGen) . If you see above results without using adcCalibration() API I'm getting results with minimum error as compared to calibrated one.

0 jagadish gundavarapu 8 months ago in reply to Vijay Wankhede

TI__Guru* 75096 points

Hi Vijay,

Apologies for the delay response.

Vijay Wankhede said:
Thanks for you'r response. I have connected J8 jumper to get 3V as Vref and Im working with respect to 3V reference only but even though at 3V I should get 4095 ADC count you can refer my test results above.

You are correct, if your reference voltage is 3v then the count should not be 3882, usually we should not get this much variation on analog measurement.

Can you tell me exactly which pin you are using for measurement>

And also, is it happening for any other pin as well?

Did you make sure your input GND connect with board GND?

--
Thanks & regards,
Jagadish.

0 Vijay Wankhede 8 months ago in reply to jagadish gundavarapu

Prodigy 90 points

Hello,

Please refer attached snippets for ADC setting:

Here are pin and ADC setting details,
And results are nearly similar for other ADC pins as well.
Yes input GND is connected to controller GND.

0 jagadish gundavarapu 7 months ago in reply to Vijay Wankhede

TI__Guru* 75096 points

Hi Vijay,

Thanks for the details,

Instead of connecting external voltage to ADC pins,

Can you please connect below highlighted ADREFHI pin to your required ADC pins and see the ADC results:

This should provide us 4095 count on ADC pins, please do this testing and update the results to me.

--
Thanks & regards,
Jagadish.

0 Vijay Wankhede 7 months ago in reply to jagadish gundavarapu

Prodigy 90 points

Hi Jagadish,

Sorry for late response, I have connected ADREFHI pin and here is the result as attached:

Getting 3944 adc count at 3V (ADREFHI)
Which is not expected correct?

0 jagadish gundavarapu 7 months ago in reply to Vijay Wankhede

TI__Guru* 75096 points

Hi Vijay,

Apologies for the delay.

I will test this one on my HDK board once and will update my results as soon as possible.

--
Thanks & Regards,
Jagadish.

0 jagadish gundavarapu 6 months ago in reply to jagadish gundavarapu

TI__Guru* 75096 points

Hi Vijay

I couldn't find my old HDK board, is it okay to setup one live debugging session to discuss on this issue further?

--
Thanks & regards,
Jagadish.

0 Vijay Wankhede 6 months ago in reply to jagadish gundavarapu

Prodigy 90 points

Hello Jagadish,

Actually one updated on this, I changed my HDK board and I found that I'm getting nearly 4095 at 3V not exact 4095 adc count but near to it.
I think for time being it's okay but accurracy is little concern. If I sense voltage at adc I see fluctuations in my adc sensing I think its expect though (also with adcCalibration API is called).
But thanks!