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DAC8742HEVM: How to verify with PACTware (or similar software) the EVM and HART master are communicating.

Steven Neves
Prodigy 20 points
Part Number: DAC8742HEVM
Other Parts Discussed in Thread: USB2ANY, DAC8742H,

Tool/software:

I am using a USB Viator HART interface, Model: HM-MT-USB-010031 along with PACTware 6.2.

I am able to verify with the DAC8472H EVM PC software that I can read registers from the HART modem via the TI USB2ANY.  Now I wish to validate the other side of the communication chain.

When using PACTware I can find my HART interface.  I connect the two leads from the HART interface into MOD_IN and MOD_OUT on the DAC8742H EVM.  After loading a generic DTM, I am never able to find the DAC8742H EVM when I do a scan of the network. 

I also tried supplying a constant 4mA current loop with a 250 ohm resister across MOD_IN and MOD_OUT to see if perhaps the PV being out of range was part of the problem and that also didn't help.

What am I missing?  Is there another method you recommend for validating the HART modem is communicating with another HART master?

  • +1
    TI__Guru* 94335 points

    Steven,


    The DAC8742HEVM doesn't have a HART stack programmed into it to decode and interpret HART commands. The EVM only is used to show the SPI/UART communication for the DAC8742H and it's relation to the HART FSK. It's not really meant to work with a HART master.

    Using the EVM, you can evaluate the physical-layer properties of the HART signal coming in and out of the device. The receive and transmit are done through a FIFO, so you may be able to read the first 16 bytes of the HART communication coming into the device from a master using the FIFO. Similarly, you can send 16 bytes of HART FSK through the FIFO, but you won't be able to send anything longer than that (unless you're using UART mode and have a separate UART source). The HART/PAFF Write/Read window in the GUI shows the data.

    Additionally, there's no transmitter setup on the board that would establish a 4-20mA loop. I'm sorry, but this EVM is much more lower-level than I think you were expecting.


    Joseph Wu