Available serial ports on the UP

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P
P New Member Posts: 11 ✭
edited March 2017 in UP Board Linux
Dear all,

as I understand the documentation there are two serial ports on the UP: One via the 40-pin GPIO on pins 8 and 10 (named "UART") and one via the additional breakout cable for connector CN7 on pins 9 and 10 (named "UART0").
I assume they are not the same UART but different ones?
I read that the one via CN7 breakout cable is /dev/ttyS0 and also features the serial console of the UP. Is the one on the GPIO header also preoccupied by some special functions (like the serial console) or is this a plain vanilla serial port. Is that port on the GPIO then /dev/ttyS1?

Additional question: Due to graphics errors with the UP-kernel 4.4.0 on Lubuntu, I now use the HWE stack of Lubuntu 16.04.2 which features kernel 4.8. Are those serial ports also accessible under kernel 4.8, i.e., not using the custom UP-kernel?

Best regards
uppetite
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  • P
    P New Member Posts: 11 ✭
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    Bump!
    Is there no official information about that?
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  • Dan O'Donovan
    Dan O'Donovan Administrator, Moderator, Emutex Posts: 241 admin
    edited March 2017
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    uppetite wrote:
    as I understand the documentation there are two serial ports on the UP: One via the 40-pin GPIO on pins 8 and 10 (named "UART") and one via the additional breakout cable for connector CN7 on pins 9 and 10 (named "UART0").
    I assume they are not the same UART but different ones?
    Correct, these are different UARTs.
    uppetite wrote:
    I read that the one via CN7 breakout cable is /dev/ttyS0 and also features the serial console of the UP. Is the one on the GPIO header also preoccupied by some special functions (like the serial console) or is this a plain vanilla serial port. Is that port on the GPIO then /dev/ttyS1?
    Correct, the one on CN7 is a basic 3-wire serial port, intended mainly for serial console or debug use. Its baud rate is limited to 115200.

    The one on the 40-pin header is a "high-speed" UART (up to 3Mbps) and has RTS/CTS hardware flow control pins available as well. On ubilinux, this one is /dev/ttyS1. On other kernel versions, the number may differ due to different kernel configurations.

    uppetite wrote:
    Additional question: Due to graphics errors with the UP-kernel 4.4.0 on Lubuntu, I now use the HWE stack of Lubuntu 16.04.2 which features kernel 4.8. Are those serial ports also accessible under kernel 4.8, i.e., not using the custom UP-kernel?
    Unfortunately, at this time, you would need some drivers from the custom UP kernel to enable the UART (or any of the I/O features) on the 40-pin header. This is because there is a CPLD in the middle which performs voltage level-shifting on those signals and it is disabled at boot by default until configured and enabled by those drivers.
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  • P
    P New Member Posts: 11 ✭
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    Thank you for that really quick answer after the bump!
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  • Mirko
    Mirko New Member Posts: 2 ✭
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    Hello.
    Was someone able to communicate with UART1 (pin 8-10 40 pins GPIO) on Windows 10?
    The port is seen as COM1 but cannot communicate.
    Is some driver needed?
    Thanks.
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  • B&E antec
    B&E antec New Member Posts: 12 ✭
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    Yes, we have successfully established communication via UART1. We created a PCB to connect via 40 pin connector and have a MAX3232 on this PCB. Works perfectly.

    However we failed to set UART0 to UART function rather than debug console. Has any Windows user (win 10 IoT 32 Bit) already used UART0 ?
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  • cujometaldog
    cujometaldog New Member Posts: 1 ✭
    edited February 2022
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    I think I figured it out!

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