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CCS/TMDSEMU110-U: XDS110's UART not works

Mark81
Expert 2610 points
Part Number: TMDSEMU110-U
Other Parts Discussed in Thread: CC3200

Tool/software: Code Composer Studio

Because I'm using a LP board to test my application I bought an XDS110 (TMDSEMU110-U) to program and debug my custom board.

After connecting the debugger to the PC (Windows 10) it installed the related drivers, also for the two CDC UART ports.

The user/application UART does not work: I monitor the pin UARTTX on the auxiliary connector but it is at 0V level. I expect a logic high on idle. Even opening the port in a serial terminal and send something changes nothing.

Do I need to set something in order to enable this UART?

  • 0
    TI__Guru**** 170244 points

    Hi,

    In the target configuration file you can set the function of the Auxiliary port as shown in the screenshot below:

    This should get your UART port working just fine. 

    Hope this helps,

    Rafael

  • 0 in reply to desouza
    Expert 2610 points
    Thanks, I set the "Aux COM port is target UART port" but I don't understand how to "download" this information to the debugger.
    I mean: if I connect the XDS110 built-in in the LP, the TX line is high and I can send data using a serial terminal - without any action from CCS!

    Now I double checked the settings above, but connecting the XDS110 (standalone) via USB doesn't change the behavior: the TX line is low.
  • 0
    Guru 92251 points

    Mark81 said:
    The user/application UART does not work: I monitor the pin UARTTX on the auxiliary connector but it is at 0V level. I expect a logic high on idle.

    Figure 1. XDS110 Probe High-Level Block Diagram in the XDS110 Debug Probe User's Guide shows there is a Voltage Translation circuit between the Target Auxiliary Connection and the Debug Control MCU inside the TMDSEMU110-U.

    The documentation doesn't clearly define how the Voltage Translation inside the TMDSEMU110-U know which logic level to drive on the Target Auxiliary Connection, and I can't find a schematic of the TMDSEMU110-U. The Target Auxiliary Connection pin 3 is labelled as "TGTVDD(Sense)" and so maybe you need to connect the Target Auxiliary Connection TGTVDD(Sense) pin to the target VDD supply to get the TMDSEMU110-U to drive the UARTTX high at the voltage level used by the target.

  • 0 in reply to Chester Gillon
    Expert 2610 points
    Yes, I've just discovered this few minutes ago. The Target VSense MUST be connected. I spent a lot of hours just to make an UART working... the documentation should clearly state that "to use the aux UART you also have to connect the vtarget pin".
  • 0 in reply to Mark81
    Guru 92251 points

    Mark81 said:
    the documentation should clearly state that "to use the aux UART you also have to connect the vtarget pin".

    I just used the Submit Documentation Feedback link on SPRUI94 to make that comment, and reference this thread.

  • 0 in reply to Chester Gillon
    Expert 2610 points
    Thanks!
    I have another question: if it's mandatory to connect the vtarget signal in order to use the UART it means it's not possible to download the firmware using only the serial connection! In fact, one should use also the JTAG connection to have the vtarget signal... It's not handy! I'm sure there is another way...
  • 0 in reply to Mark81
    TI__Guru**** 170244 points
    Hi,

    Please apologize for the delay and thank you for your feedback; we are going to modify our XDS110 documentation to properly inform the users about the UART functionality.

    >> if it's mandatory to connect the vtarget signal in order to use the UART it means it's not possible to download the firmware using only the serial connection!
    You are correct. If you intend to perform a firmware download to a target similarly as to what is done in, say a CC3200 Launchpad, the Vtarget pin on the XDS110 will have to be properly powered. The UART on the XDS110 was not originally intended to perform this operation.

    Please apologize for the inconvenience,
    Rafael