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Does PRU UART work well for 38400 baudrate on OMAPL138 EVM ?

sweta bhatt
Expert 2345 points

Hi,

We are planning to get additional soft UARTs by implementing PRU UART on OMAPL138EVM.

We integrated the latest patch for DaVinci-PSP-SDK-03.20.00.12 release and with this, we get PRU UART transmit (from EVM) working for various standard baudrates except 38400 bps. Receive (to EVM) at 38400 bps is working fine, whereas transmit at 38400 bps shows junk characters.

We use teraterm/hyperterminal on host PC side.

We run EVM at 300 MHZ. Does any one know, why it is not working specifically for 38400 bps ?

Interesting observation is, when I transmit data at 38400 bps, I can receive that data on PC side at 115200 properly, but not at 38400 bps.

Is there any bug in PRU SUART driver for transmit at this baud rate? Has anyone faced any such issue with PRU UART ?

Thanks,
Sweta

  • 0
    TI__Genius 15920 points

    Hi Sweta,

    By default, the soft UART code does not support 38400 baud.  The code defines a base baud rate (115200 by default) and other baud rates are achieved by prescalars, or divide by factors.  The code supports the following prescalar/ divide by numbers:

           1, 2, 4, 6, 12, 16, 24, 48, 64, 96 & 192

    Since 38400 requires a prescalar of 3 (115200 / 38400 = 3), it is not supported with the base baud rate = 115200 configuration.

    To achieve 38400, you can change the base baud rate (SUART_DEFAULT_BAUD) in pru/hal/uart/include/suart_api.h to 38400 (line 81).

    Refer to the Quick Start Guide for additional details-- http://mistralsolutions.com/pes-support/support-downloads/l13x-daughter-card-documentation-software.html.

    Regards,

    Melissa