How to enable CN8 UART RTS(on GPIO4)?

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pna
pna New Member Posts: 7 ✭
edited January 2023 in UP Squared V2 Linux

Hello,

I am using Ubuntu 22.04 and is testing the UART on CN8 (mapped to /dev/ttyS6). However, I can't get the UART RTS to work. Is there anything I need to configure to get this working?

Thanks.

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  • Wilbert
    Wilbert New Member Posts: 168 ✭✭✭
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    Hi Sir,

    Can you provide BIOS version?

    Best Regards,
    Wilbert Lee

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  • Wilbert
    Wilbert New Member Posts: 168 ✭✭✭
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    Hi Sir,

    We have UART/COM on our board, can both not be used? Or only UART on HAT40 can't be used?

    Best Regards,
    Wilbert Lee

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  • pna
    pna New Member Posts: 7 ✭
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    Hello @Wilbert ,

    Sorry for the late reply. The BIOS-version is USEHAM10. The UART on the HAT40 works fine (I am able to send and receive data on this port), however, I am not getting the hardware flow control signals to work (RTS and CTS). Is there anything in BIOS that must be configured? I have gone through the BIOS as admin to check, but I could not find anything that seemed related.

    Thanks.

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  • Wilbert
    Wilbert New Member Posts: 168 ✭✭✭
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    Hi Sir,

    May I ask what tool you use? Have you adjusted the corresponding settings?
    Generally, the BIOS only chooses to enable or disable UART, and does not independently set whether to support RTS/CTS. Beaause this can be adjusted through the tool.

    Best Regards,
    Wilbert Lee.

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  • pna
    pna New Member Posts: 7 ✭
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    Hello @Wilbert,

    Thank you for the answer. I have tested with both minicom and picocom. I have enabled hardware flow control in both, but this did not have any effect.

    Thanks.

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  • Wilbert
    Wilbert New Member Posts: 168 ✭✭✭
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    Hi Sir,

    Sorry for replying to this question so late.
    How did you test it? IO wiring method?
    My actual measurement here is to use the R1.0 version of the BIOS without modifying any BIOS settings, install Ubuntu 20.04, Kernel 5.15.0-46, and use minicom.
    The test result is PASS. I directly shorted TX/RX and RTS/CTS, and it can be transmitted normally. When the RTS/CTS is disconnect, it cannot be recived.
    Using an oscilloscope to measure, you can see that when transmission is required, RTS will turn to Low. (At this time, RTS and CTS are disconnected and there is no connection)

    Best Regards,
    Wilbert Lee

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