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TMS320F2800135: Maximum SCI Baud Rate Q&A

Lawrence Wang
Intellectual 805 points
Part Number: TMS320F2800135


Tool/software:

Hi experts,

My client has the following application: Use the maximum baud rate of SCI to send data (LSPCLK/16 = 7.5mbps). The client will use 2 high-speed UART interfaces, 1 low-speed UART to receive 100 bytes of data per second, and one high-speed UART to receive about 7.125mbps of data. In the application, these data will be packaged and timestamped by a timer. Then they will be sent out through the high-speed UART serial port at a rate of 7.5mbps. It is known that the size of the data packet to be sent is about 7.125mbps. Will this work? Because I found that our SCI does not have DMA, only fifo. Can this fifo be used and can it be implemented in this application?

  • 0
    TI__Mastermind 20770 points

    Hi Lawrence,

    You are correct, the SCI peripheral does not have DMA access (and F280013x also doesn't have a DMA). For high speed receives of UART data, I would suggest enabling the RX FIFO (as you've mentioned) and taking an interrupt-based approach for the high-speed SCI to ensure data is being read out of the RX FIFO fast enough (and no overwrite data loss happens). For the low speed UART, you can poll the RX FIFO in the background loop so that the operation is interruptable (assuming the program allows for this). Note that two SCI instances operate completely separate of each other, the only concern with interference would be with CPU operations. A couple questions I have:

    1. The SCI RX interrupt is relatively low priority in the PIE, are they using any other interrupts in their application that could delay the SCI RX ISR execution?
    2. What else is going on in their main loop? Is it time critical?
    3. What is the size of the packet being sent? This will help determine the proper FIFO level to use.
    4. Also note that you may see some error with using the SCI baud rate at its maximum. What is their hardware setup? They will want to avoid noise on the SCI RX pin as much as possible.

    Best Regards,

    Delaney