TMS320F280049C: ADC issue

Adrien Thurin

Part Number: TMS320F280049C
Other Parts Discussed in Thread: LAUNCHXL-F280049C, SYSCONFIG

Hi,

I have an issue with ADCs on my LAUNCHXL-F280049C board.

I have used sysconfig to configure them, in a way that looks very similar to TI driverlib examples. However, they behave in a very strange way.

When I connect the ADC pins to +3.3V, I read 0xFFF as expercted. But when I connect it to 0V, the reading oscillates (lowest value seen : 0x142 ; highest : 0xFFF) instead of maintaining a proper 0x000. The ADC reads 0x000 when the pin is left unconnected.

The problem is the same on all ADC inputs I tested. I have confirm there is actually 0V on the pin with an oscilloscope.

I use the board in "standalone" : the only connexion to something else is the USB for debug, and the only "modification" I did is to flip the S6 switch.

I can provide the project if needed (same as in this post).

I suspect something very basic. For instance, I didn't see the usual ADC calibration function in the driverlib ADC files, could it be the source of the problem ?

Thanks in advance,

Adrien

over 3 years ago

+1 Ibukun Olumuyiwa over 3 years ago

TI__Genius 11081 points

Adrien,

In your project, you have configured the system for external reference mode. Can you confirm that you have a 3.3V reference driver connected to the VREFHI header on the launchpad (and 0V to the VREFLO pin)?

Thanks,
KIbukun

0 Adrien Thurin over 3 years ago in reply to Ibukun Olumuyiwa

Intellectual 546 points

Hi,

Now I feel very silly. I have checked the launchpad schematic several times and missed the fact that the voltage reference was left unconnected.

Of course, when connected to the 3.3V supply, the ADCs behave as expected.

Thank you very much for your help, and my apologies for this very basic question.

Adrien

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TMS320F280049C: ADC issue