TMS570LS20216A ADC

Mike Stevens

I am new to the forum and have been using a TS570 for a few months with the IAR ARM IDE. I have my application using the ADCs running fine while under JTAG debug, but when running "stand-alone" the ADC channel (the one that I am displaying) always reads zero.

I (think I) have all the clock selects and peripheral enables set correctly and the processor clock is the same in the 2 modes, but there must be something else I have missed.

Any ideas of what that might be?

Thanks in advance.

Cheers,

Mike.

over 13 years ago

0 Brian Fortman over 13 years ago

TI__Expert 7650 points

Hi Mike,

One of our experts on this subject will get back with you shortly.

Best Regards,

Brian

0 Mike Stevens over 13 years ago in reply to Brian Fortman

Prodigy 60 points

Hi Brian,

Thanks for that. I will keep an eye out for your experts.

Cheers,

Mike.

0 Diwakar Bansal over 13 years ago in reply to Mike Stevens

TI__Intellectual 1325 points

Hello Mike,

Can you please tell us how nTRST pin is hooked up on the board?

Regards,
Diwakar

0 Mike Stevens over 13 years ago in reply to Diwakar Bansal

Prodigy 60 points

Hi Diwakar,

nTRST is pulled down with a 10k resistor and connected to the JTAG connector (of course).

I have some more information. When running stand-alone, most ADC channels read zero, but some read non-zero. This is with the same actual voltages on the device pins.

Thanks.

Cheers,

Mike.

0 Mike Stevens over 13 years ago in reply to Mike Stevens

Prodigy 60 points

I have even more information! Having now got a local diagnostic port running using an external SPI based UART, I can extract more diagnostic information when in 'stand-alone' mode. It seems that the ADC channels are reading as though they have a -1.5V offset on their inputs (they don't as I have measured the actual voltages on the pins). So, a voltage of 2.47 converts as 0.97, a 1.05 converts as 0.

Cheers,

Mike.

0 Sunil Oak over 13 years ago in reply to Mike Stevens

TI__Mastermind 49120 points

Please check the health of the ADREFLO pin. Is it truly at 0V?

Regards, Sunil

0 Mike Stevens over 13 years ago in reply to Sunil Oak

Prodigy 60 points

Both pins 64 (VSSAD) and 65 (ADREFLO) measure 0.005V, (with a DVM), WRT board 0V.

But - why would this make the difference between dubug and stand-alone mode?

Cheers,

Mike.

0 Mike Stevens over 13 years ago in reply to Mike Stevens

Prodigy 60 points

Problem solved!

the ADC CAL registers were getting set with the wrong values, despite the calbrate function. I suspect I had an uninitialised variable that was stopping it running correctly, but I can't quite see the actual mechanism of that.

Having corrected the uninitialised variable, it now all seems to work!

Thanks.

Cheers,

Mike.

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TMS570LS20216A ADC