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TMS320F280039: writing 0x07 to ADCDACLOOPBACK register

Viktorija Cecil
Mastermind 18501 points

Part Number: TMS320F280039

Team, 

My customer is using the TMS320F280039 on a LAUNCHPAD-XL.  They have run into a problem using the ADCDACLOOPBACK register: 

  • We attempt to write 0x07 to it, using the ASysCtl_enableADCDACLoopback() function but it appears to set it to 0x05 instead.  

Can you give some guidance how to write 0x07?

Thanks

Viktorija

  • 0
    TI__Genius 11081 points

    Hello Viktorija,

    This appears to be a silicon bug; I am following up with our design team. There are a couple of potential workarounds.

    • Assuming the intent is to test the functionality of the ADC, you could use one of the two buffered DACs to output a known voltage, and sample it using ADCB. The output of DACA is on the same pin as channel B15, and the output of DACB is on B7.
    • Use the INTERNALTEST/ADC gain balancing mechanism to sample VREFHI. This is currently undocumented in the released TRM but will be documented in the next revision, which should be published in the near future. In the meantime, I can share details with you privately if needed.

    Please note that all of these methods (including ADCDACLOOPBACK) require much longer ACQPS settings for accurate conversion.

    Best regards,
    Ibukun