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DAC8832EVM-PDK: .xml files unable to be downloaded by DXP, EVM not working

Carolus Andrews
Mastermind 18780 points
Part Number: DAC8832EVM-PDK
Other Parts Discussed in Thread: DXP, , DAC8832

Team,

I am in the process of setting up a DAC8832EVM-PDK, and I am unable to download the needed drivers via DXP. Regardless of what file I attempt to download via the SW, I receive the message "Unable to download XXXXXX.xml."

After doing some digging, I found the previous post on the forum addressing the same issue:

I followed the instructions using the file uploaded by Sam, and this allows me to pull up a "driver" for the DAC8832, but when I attempt to run the program, there is no output from the EVM apart from a solid DC signal, regardless of the state of the SW (DAC ON vs. DAC OFF)

Any advice to get this up and running would be appreciated.

  • 0
    TI__Genius 14220 points
    Hi Carlous,

    You can look at the following query:

    e2e.ti.com/.../2179805

    You will need to install the dxp-supportpackage from the FTP site.

    Regards,
    Uttam Sahu
    Applications Engineer, Precision DACs
  • 0 in reply to Uttam Sahu
    TI__Mastermind 18780 points

    Dear Uttam,

    I followed the link and installed the DXP support package (I was only able to install 1.0; 2.0 informs me that my TI profile does not have adequate permissions to install) as well as re-installing the DAC8832.xml file. As a result of this, DXP will now start up without prompting me to download an EVM file, and I am able to select DAC8832 from the list of available EVMs.

    However, from the moment I plug the 6V adapter into the EVM, the DAC output at pin 2 of the connector becomes a constant voltage equivalent to just shy of 4V (is there an internal pullup?). This voltage does not change, regardless of whether DXP is actively sending a signal or not, indicating that I have a saturation issue somewhere. I have verified that the 6V in is correctly 6V, and the voltage pins at the EVM are socketed to the MMB0 correctly. I have also verified that the Vref and Vcc are present to the device.

    The MMB0 is outputting a code on the LCD display that looks like a 5 with the top segment missing. The dot in the lower right corner of the display is also lit. I have probed several power supplies on these (I have two MMB0's, both of which exhibit the following), and I have noticed that the negative voltages are not present on either board. However, where the voltage SHOULD be -5V, (measured at capacitor C7, node "-V" of the user's guide schematic), I am getting roughly the same voltage as on the output. Between the voltages on the V+/V- pins of U1, I am measuring a dynamic range of ~4V - 5V, or about a 1V swing well above the reference voltage. This doesn't seem right, and would answer why I'm saturating to 4V. Is there a modification that needs to be made to the MMB0 motherboard to get it to produce a negative voltage? Do I need to bring in a separate supply at the terminal block to provide the negative voltage on that pin? This seems dangerous, as I am getting a positive voltage on that pin that could cause issues if I try to drive it with -5V externally, and the others measure fine. I can't rely on the User's Guide b/c the schematic and discussion there are Rev C of the board, and the boards sent to me are Rev D, which show significant changes to the layout and design.

    That said, I've pored over the User's guide available, and it looks like this should have been plug and play, so I'm curious as to what could be happening. Any advice on how to get this up and running would be appreciated.

  • 0 in reply to Carolus Andrews
    TI__Genius 14220 points
    Hi Carolus,

    Good to know that you could install DXP properly.

    Regarding the saturation issue you noticed, it is because of the absence of a negative power supply. Both MMB0 and DAC8832EVM do not generate the -5V and hence you need to provide that separately though the terminal block J1 on MMB0.

    Regarding the voltage already on the -V node, it's because the node is floating without a -5V connection and the output opamp U1 on DAC8832EVM causes that voltage to appear, probably due to charging of the decoupling capacitor C7. However, there is nothing to worry - this is not acting like a voltage source. The moment you connect the external source it will disappear.

    If you connect the negative supply and follow the procedure, everything should be plug and play. I have tried this myself before writing this.

    Regards,
    Uttam
  • 0 in reply to Uttam Sahu
    TI__Mastermind 18780 points

    Uttam,

    Indeed, I was able to verify this myself on Friday. Everything appears to be in working order. Thanks for helpiong me to get this up and running.