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DAC8742HEVM: doesn't work in SPI mode

Roman Knapczyk
Prodigy 20 points

Part Number: DAC8742HEVM
Other Parts Discussed in Thread: USB2ANY

I use DAC8742HEVM with default settings (HART mode, power supply from USB2ANY, SPI mode selected in GUI). From the DAC8742HEVM GUI in high level configuration I generate write or from Low level configuration I set MOD_EN and RTS bits in MODEM_CONTROL register. After that I expect HART signals on MOD_OUT (1200Hz or 2200Hz). Unfortunately it doesn't work. 

If I measure with oscilloscope SPI signals CS and CLK on J6 connector there are no transitions. I think the USB2ANY doesn't work in SPI mode or something like that. The status LED on USB2ANY is blinking constantly.

See at the pictures below for my board configuration and GUI settings.

I would be grateful for your help. Thanks.

  • +1
    TI__Guru** 100805 points

    Roman,

    I'll need to test this a bit more and get back to you. I'm having some problems running the software right now.

    One easy thing that you can check is to check the reference voltage output on TP1. Measuring that, you can see the 1.5V reference when the precision reference is enabled and shut off when it's disabled. This can be checked through the SPI interface, and you can see if the USB2ANY is really not sending a signal.


    Joseph Wu

  • 0
    Prodigy 20 points

    Hello Joseph,

    thanks for your help. The 1.5V reference was disabled. When I enabled the internal reference in the GUI, then I could measure the HART signals (1200Hz, 2200Hz) on MOD OUT. I used "Generate write" feature (5x 0xFFs) to send data over SPI bus.