On Wed, Apr 21, 2021 at 6:24 PM Peter Robinson <[email protected]> wrote:

> > I have an Nvidia Jetson Nano that I was gifted by the Fedora project to
> troubleshoot some arm specific packaging issues. That's done now so I
> decided to see what else I could do with it.
> >
> > I found NodeRED which had a module for the Raspberry Pi to control the
> GPIO. I have since forked that project and have made some progress porting
> it to the Nano.
>
> From a GPIO PoV you should look at libgpiod and related pieces for
> access to the GPIO, there's some threads about this on the mailing
> list so look at the archives as a starter.
>

That's essentially what I did, but I'm currently using the utilities
(gpioset, gpiomon) so I don't need python which reduces the number of
dependencies.



> > Now I want to see if I can get the serial header working. From what I
> can tell if running the linux OS provided by Nvidia there should be a
> serial device named /dev/ttyTHS1 but it's not getting detected AFAICT
> grepping through dmesg.
>
> The nano has two types of serial port, a traditional 8250 style UART,
> of which the driver is built into the kernel as it's needed for the
> serial console. The debug UART is the only one of those that is
> enabled by default but there is 4 of them, there's also the HS UART
> which is a high speed UART.
>

I'm guessing it's the latter, but yes, I want to use the serial on the J41
header in NodeRED.



> > I found the page for the serial-tegra that should be in the linux kernel
> but if I try:
> >
> > # modprobe serial-tegra
> >
> > Nothing happens, no output if I try adding "-v" as an option either. So
> does the module exist or not? If I try some random name in modprobe it
> gives an error which makes me think it's present, but it doesn't load and
> doesn't give me any helpful reason why.
>
> I don't see the hsuart in the device tree, but there's some notes
> there, I believe you need to configure one or the other but it will
> likely need changes to the device tree which is why you won't see it.
>

So serial-tegra is not the correct way to go?


I'm also not sure what the hsuart has to do with GPIO.
>

It doesn't directly, but pins 6, 8, & 10 of the J41 header (generically
referred to as the GPIO header) is for serial use.

Thanks,
Richard
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