UARTing into RPi 2

UARTing into RPi 2

[Daniel Morandini]

Hi folks,
I recently flashed a microSD card with the official RPi image [1]. 

Connecting my Adafruit USB to TTL cable [2] to the right pins [3] and issuing a `cu -l /dev/<the cu device> -s 115200` gets me a terminal session on both FreeBSD and Raspbian (these are the ones I used), but it does not happen with plan9 unfortunately.

I hacked just one thing after this first attempt (which did not work though): I added the “enable_uart=1” line to the config.txt file.

I’m wondering if there is someone in this community that could enlighten me on these issue. There is a certain level of “naivity” from my side here, but I’m very curious and interested. plan9’s concepts look game changing to me!

Ciao,
Daniel

[1] https://9p.io/sources/contrib/miller/9pi.img.gz
[2] https://www.adafruit.com/product/954
[3] https://pinout.xyz/pinout/uart#
[4] https://www.raspberrypi.org/documentation/configuration/device-tree.md#part4.6

Re: [9fans] UARTing into RPi 2

[Richard Miller]

Add to the end of the command line in cmdline.txt:
  console='0 b115200'
and you should see a shell prompt on the serial port when you reboot.

Setting up a serial port login (for an arbitrary user) would be
a bit more complicated...

Re: [9fans] UARTing into RPi 2

[David du Colombier]

You should add "console='0 b115200'" at the end of kernel boot
parameters in cmdline.txt.

Also ensure that you have "core_freq=250" set for pi3 and pi4
in config.txt, which should be already the case if you're using
Richard Miller's RPI image.

-- 
David du Colombier

Re: [9fans] UARTing into RPi 2

[Daniel Morandini]

Dear Richard and David,
Thank you for the prompt reply, I’ll check it out as soon as possible.

May I ask you why this line is required? What does it do?

> On 10 Apr 2020, at 10:45, Richard Miller <9fans@hamnavoe.com> wrote:
> 
> Add to the end of the command line in cmdline.txt:
>  console='0 b115200'
> and you should see a shell prompt on the serial port when you reboot.
> 
> Setting up a serial port login (for an arbitrary user) would be
> a bit more complicated...
> 
> 
> ------------------------------------------
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> On 10 Apr 2020, at 10:45, David du Colombier <0intro@gmail.com> wrote:
> 
> You should add "console='0 b115200'" at the end of kernel boot
> parameters in cmdline.txt.
> 
> Also ensure that you have "core_freq=250" set for pi3 and pi4
> in config.txt, which should be already the case if you're using
> Richard Miller's RPI image.
> 
> -- 
> David du Colombier
> 
> ------------------------------------------
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Re: [9fans] UARTing into RPi 2

[Aleksandar Kuktin]

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>On Fri, 10 Apr 2020 09:45:00 +0100
>Richard Miller <9fans@hamnavoe.com> wrote:
>
> Add to the end of the command line in cmdline.txt:
>   console='0 b115200'
> and you should see a shell prompt on the serial port when you reboot.

>On Fri, 10 Apr 2020 10:45:51 +0200
>"David du Colombier" <0intro@gmail.com> wrote:
>
> You should add "console='0 b115200'" at the end of kernel boot
> parameters in cmdline.txt.

Wow, you guys were literally seconds apart with your answers. What are
the odds? xD

--
You don't need an AI for a robot uprising.
Humans will do just fine.
--

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Re: [9fans] UARTing into RPi 2

[David du Colombier]

> Wow, you guys were literally seconds apart with your answers. What are
> the odds? xD

Haha! Seems like we're synchronized somehow :-)

-- 
David du Colombier

Re: [9fans] UARTing into RPi 2

[Richard Miller]

> Wow, you guys were literally seconds apart with your answers. What are
> the odds? xD

It's a conspiracy.

Re: [9fans] UARTing into RPi 2

[Richard Miller]

> May I ask you why this line is required? What does it do?
> 
>> On 10 Apr 2020, at 10:45, Richard Miller <9fans@hamnavoe.com> wrote:
>> 
>> Add to the end of the command line in cmdline.txt:
>>  console='0 b115200'

Try running
  man plan9.ini | p
for the whole story.

Cmdline.txt on a rpi plays the role of the plan9.ini file
on a pc, except that all the parameters are on a single line,
so the values must be quoted if they contain spaces.

Re: [9fans] UARTing into RPi 2

[Daniel Morandini]

Thank you guys!
Bye 👋

Daniel

> Il giorno 10 apr 2020, alle ore 15:50, Richard Miller <9fans@hamnavoe.com> ha scritto:
> 
> 
>> 
>> May I ask you why this line is required? What does it do?
>> 
>>>> On 10 Apr 2020, at 10:45, Richard Miller <9fans@hamnavoe.com> wrote:
>>> 
>>> Add to the end of the command line in cmdline.txt:
>>> console='0 b115200'
> 
> Try running
>  man plan9.ini | p
> for the whole story.
> 
> Cmdline.txt on a rpi plays the role of the plan9.ini file
> on a pc, except that all the parameters are on a single line,
> so the values must be quoted if they contain spaces.
> 
> 
> ------------------------------------------
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