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Original question:

AM620-Q1: Maximum Baud Rate for UART

AM620-Q1: How To Interface With PRUSS UARTs

Paul Stamm II
Prodigy 75 points
Part Number: AM620-Q1

Greetings!

In Section 7.4.7 of the TRM for this family of processors (Literature #SPRUIV7B), it names two UART peripherals as part of the PRUSS subsystem (PRUSS0_UART0 and PRUSS1_UART0).

In page 2 of the datasheet (Literature #SPRSP58B), it likewise says "UARTs" under the PRU Subsystem heading, implying that there is more than one.

My confusion comes from locating the signals/pin to access both of the UARTs in the PRUSS subsystem. In Section 6.3.21 of the datasheet, Table 6-50, I can see the signal descriptions of UART for PRUSS0. In Table 6-51, however, I cannot see descriptions of UART for PRUSS1.

Does this family of processors support two UARTs in the PRUSS subsystem? Where may I find the needed information to interface with it?

Thanks for your time.

  • +1
    TI__Guru** 101910 points

    Hello Paul,

    That is a typo in the TRM chapter, probably from copying over from AM64x which has two PRU subsystems, where each PRU subsystem has a single hardware UART module. The AM62x only has one PRUSS instance. That PRU subsystem contains two PRU cores, but only one hardware UART. I'll file a bug against the TRM.

    I assume you are looking to control the PRU Hardware UART from Linux? There is a requirement for that driver to be ported to AM62x, but it does not look like the driver has been ported yet as of SDK 9.1. I am double-checking on the expected timeframe.

    There is also the option of using the PRU cores to manually generate a UART interface - we call that "soft UART". At this point in time our developers do not have concrete plans to port the AM335x soft UART code to AM62x, but that is absolutely something that you could implement if you have the need for multiple additional UARTs and the development cycles: https://software-dl.ti.com/processor-sdk-linux/esd/AM335X/09_01_00_001/exports/docs/linux/Foundational_Components/PRU-ICSS/Linux_Drivers/pru-sw-uart.html

    Regards,

    Nick

  • 0
    TI__Guru** 101910 points

    Hello Paul,

    I haven't heard back from the developer yet. I'm pinging again to see if we can get a tentative timeframe for enabling PRU Hardware UART to be controlled from Linux.

    Regards,

    Nick

  • 0 in reply to Nick Saulnier
    Prodigy 75 points

    Hi Nick,

    Thanks for the follow up!

    In recent days our customer informed us that they are relaxing their initial requirements for the Serial Comms, so at the end of the day the extra PRUSS UART channel most likely will not be needed. In light of that I circled back here to at least "close the thread" just so it wouldn't get left open forever.

    Please keep me posted, however, as the information may be useful to others!

    Kind Regards,

    Paul

  • 0 in reply to Paul Stamm II
    TI__Guru** 101910 points

    Hello Paul,

    I appreciate that, thanks for circling back. I'll have a strategy chat with the developer sometime in the next couple weeks to work out our execution plan for the coming months, and I'll update the thread after that sync.

    Regards,

    Nick