GoodOldJack12
Posts: 16
Joined: Tue Nov 29, 2016 9:39 pm

Serial connection with dumb terminal

Sun Sep 03, 2017 3:21 pm

Hello!

I'm trying to make a serial connection between the Pi3 and an Alcatel Minitel, but I'm having some issues.
I realize that there are a lot of guides on this, but those are all from before the Pi3 or before /etc/inittab was removed. Additionally,
my minitel is apparently a different, but similar model, so I had a lot of experimenting to do (and I still dont know when a certain key combinaton actually worked)

So the minitel, as far as I know, supports these baud rates: 300;1200;4800.
I have a logic converter between them, because the minitel doesnt use 3.3V.
I'm using 8 data, no parity and 1 stop bit, since I came to understand that the pi does not support parity.

I tried making a test connection with both minicom and screen. In the moments that I got the minitel config and Pi config somewhat lined up, the only output I got from both sides was garbage. (not the same characters, strange characters etc). But there IS a connection (yay).
When the pi boots, I do get something on my minitel (and a 'beep' sometimes, which is cool). But as I said, completely incomprehensible.

I've tried all the different baud rates with minicom and screen, but I cant get this to work.
I hoped to get some advice or answers here, for example:
what baud rate I should try / how to find out which one to use,
wether or not I need to swap the miniUART with the bluetooth one,
wether or not and how I should change the encoding of my terminal
or any advice at all.

Thanks in advance.

epoch1970
Posts: 5596
Joined: Thu May 05, 2016 9:33 am
Location: Paris, France

Re: Serial connection with dumb terminal

Mon Sep 04, 2017 9:08 am

I've always thought Minitels were using an asymmetric serial speed of 1200 bauds down, 75 up?
"S'il n'y a pas de solution, c'est qu'il n'y a pas de problème." Les Shadoks, J. Rouxel

GoodOldJack12
Posts: 16
Joined: Tue Nov 29, 2016 9:39 pm

Re: Serial connection with dumb terminal

Mon Sep 04, 2017 1:39 pm

The default is 1200. I dont know about the up speed. The manual gives me key combinations to set the baud rate, but unlike the other ones that I figured out, I'm not getting a physical confirmation that it worked

dgordon42
Posts: 792
Joined: Tue Aug 13, 2013 6:55 pm
Location: Dublin, Ireland

Re: Serial connection with dumb terminal

Tue Sep 05, 2017 4:32 pm

How are you setting the baud value on the Pi?

I know nothing about the Minitel, but assuming that the both the Tx and Rx baud is 1200, trying changing the phrase "console=serial0,115200" to "console=serial0,1200" in the '/boot/cmdline.txt' file.

Note 1: '/boot/cmdline.txt' must only contain 1 line. Do not split the line when editing, or try to add comments.
Note 2: Setting the Console to 1200 baud may slow down your boot time a bit.

Hope this helps,
Dave.

GoodOldJack12
Posts: 16
Joined: Tue Nov 29, 2016 9:39 pm

Re: Serial connection with dumb terminal

Sun Sep 10, 2017 1:33 pm

Hi dave,

For now I've been testing with the minicom utility. But I will try that.
I was also wondering how the stop bits and parity are handled when using the serial console

dgordon42
Posts: 792
Joined: Tue Aug 13, 2013 6:55 pm
Location: Dublin, Ireland

Re: Serial connection with dumb terminal

Sun Sep 10, 2017 2:32 pm

You can read and/or set Serial Port parameters with the 'stty' command. There is a lot of information on it's man page.

Hope this helps,
Dave.

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