TMS320F28379S: Comparator internal DAC issue

Jiakai Ye

Expert 1210 points

Part Number: TMS320F28379S

I'm writing code for F2837x comparator, the program compares CMPIN1P to 2 internal DACs. The results are

pulled out by output X-bar to GPIO14 and GPIO24. The program represents graphically in the following schematic:

CMPIN1P comes from DAC-A, the program runs at F28379S and the waveforms display as below:

The 2 internal DACs are set to different values but CMPSS1.CTRIPOUTH and CMPSS1.CTRIPOUTL are same.

But the outputs from GPIO14 and GPIO24 are correct if I change the code in function Task_1() in file TestCompOut.c from

fVDC2 = 1.0;
fZOH1 = fVDC2;
fVDC3 = 1.5;

fVDC2 = 1.5;
fZOH1 = fVDC2;
fVDC3 = 1.0;

The waveforms display as below:

Is this a hardware bug or some register settings are wrong?

Since the project is generated by a software, the initialization code is included in a library. The initialization

actions can be only confirmed from register values.

The project can be reached from the following URL:

drive.google.com/open

thanks,

Jiakai

over 7 years ago

0 Frank Ankapong over 7 years ago

TI__Mastermind 28275 points

Hi Jiakai,

That is indeed strange. Unfortunately we can't access google drive from our network. Can you verify that in the first instance where the output is not what you expect that the CMPSS is indeed what you programmed it to be?

0 Jiakai Ye over 7 years ago in reply to Frank Ankapong

Expert 1210 points

Hi Frank,

I have attached the whole project for your review.

I use F28379D control card (see picture below) to test it again, no change at all.

thanks,

Jiakai

TestCompOut_20190112.zip

0 Frank Ankapong over 7 years ago in reply to Jiakai Ye

TI__Mastermind 28275 points

Jiakai,

I think the problem is coming from the way you are initializing the variables. Please check DACHVALS/A and DACLVALS/A in the watch window to make sure they are written to the values being computed in the code for the problem case. I think you will find out one of them is not. And with that, you can work your way back to find out the issue.

0 Jiakai Ye over 7 years ago in reply to Frank Ankapong

Expert 1210 points

Hi Frank,

I have checked the schematic again and found that I set Output2 of Output X-Bar to

CMPSS1.CTRIPOUTH and CMPSS1.CTRIPOUTL, if I remove CMPSS1.CTRIPOUTH

from Output2 the 2 Output X-Bar work fine.

I am sorry for this mistake.

Regards,

Jiakai

0 Frank Ankapong over 7 years ago in reply to Jiakai Ye

TI__Mastermind 28275 points

No problem. Glad you were able to resolve it! Let us know if you run into anymore issues.

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TMS320F28379S: Comparator internal DAC issue