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AWR1642BOOST: MSS_UARTB duplex capability

ej99
Intellectual 640 points
Part Number: AWR1642BOOST
Other Parts Discussed in Thread: AWR1642

I am trying to use MSS_UARTB (aka UART3) as a full duplex UART with RX and TX. I can see that there are pins that can be muxed to the MSS_UARTB_RX signal according to the datasheet - N4 and P4. However, I noticed that in the UART driver, there is a configuration which says UART3 is TX only. (This is in drivers/uart/platform/uart_xwr16xx.c) It also says in this file that "This should *NOT* be modified by the customer." It doesn't make a whole lot of sense to me that you would go through all the trouble to mux the UART3 RX signal out if it can't do RX. I suspect this is an error in the UART driver. I'm hoping that a TI engineer can confirm that I can change this configuration without breaking something, since there is that warning.

You might wonder why I care about this. I am trying to get a bidirectional UART without going through the USB connector. Since both of the pads that could be used for MSS_UARTA_RX are wired to other peripherals on the AWR1642BOOST, the only option seems to be MSS_UARTB. I tried modifying the mmWave Demo by setting the pinmux to set P4 to RX for UARTB and then swapping the indices for the UART_open() calls for the command and logging UARTs so that UARTB became the command UART (since that uses full duplex). When I tried running this, I just got an endless stream of mmwDemo:/> prompts being output to the command port. It didn't appear to be listening. After a while, I realized this was probably happening because of the driver configuration I have described.

  • 0
    TI__Mastermind 22155 points
    Hello Erich,

    The UART3 is intended for only logging functionality for the application code(TX only ). It is not intended for the full duplex functionality.


    I am not able to understand the need for the extra bidirectional UART in your design . Are you looking for bypassing the CLI or use of USB to send configuration to the device ?

    -Raghu
  • 0 in reply to Raghunandan Kamath
    Intellectual 640 points

    I would like to set up serial communication to another device using the pin headers on the EVM, rather than the USB connector. The motivation is that USB cables are bulkier, less mechanically secure, and require additional hardware on the other device. Using a direct UART connection will also more closely resemble what I would eventually do with a custom board.

    If UART3 is indeed TX only, can you explain why there is an MSS_uartb_rx signal that can be muxed to pins? See pp.15-16 of the AWR1642 datasheet. Also, on p.1 in Features, the datasheet says "Up to 2 UARTs." If you are counting full-duplex UARTs, that would be 1, and if you're also counting TX-only UARTs, there are 3 because of the DSS logger. Now, if UART3 is also full-duplex, then it would make sense to say 2 UARTs.

    When you say UART3 is intended for TX only, are you referring specifically to the mmWave demo, or an inherent hardware limitation? My question is about the hardware capability. If there is a driver change that I need to make, I'm willing to do that.