CCS/TMS320F28379D: Normalizing the ADC output values

Sainath Reddy Samireddy

Tool/software: Code Composer Studio

Hello All,

This is Sainath. Firstly, I would like to thank you guys because I've been receiving a great help for all of you in resolving different issues in coding. I just need some help in rescaling the ADC output values from the scale of [0 4095] to the range of [-1,1].

I'm using the sample code adc_soc_epwm from the control suite. I tried to write some logic for normalizing but I was not successful in doing it. Can anybody help me in normalizing the ADC values.

Thank you.

Sincerely,

Sainath Reddy.

over 8 years ago

0 Devin Cottier over 8 years ago

TI__Guru 60865 points

Hi Sainath,

What logic did you try and how did it fail to work? I think roughly you want to subtract half the range (so the results are -1/2 range to +1/2 range), then divide by that same value of half the range (so the results are -1 to +1).

0 Sainath Reddy Samireddy over 8 years ago in reply to Devin Cottier

Intellectual 400 points

Hello Devin,

Thanks for your reply. I tried to rescale the ADC values in the adc_isr. My normalizing logic is:

normalized_sample = (2*Adcaresults[resultsIndex])/4096 - 1;

But for this logic, the output is always remaining at zero and not giving any floating point values.

Thank you.

Regards,

Sainath Reddy.

0 Devin Cottier over 8 years ago in reply to Sainath Reddy Samireddy

TI__Guru 60865 points

Hi Sainath,

Since the ADC results are an integer and all your other constants are integers, the compiler is generating an integer division. Try replace\ing 2 with 2.0, 4096 with 4096.0 and 1 with 1.0.

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CCS/TMS320F28379D: Normalizing the ADC output values