Serial port issues

pankaj13 · n00b Joined: 05 Sep 2019 Posts: 29

Hi,

I am trying to flash Tasmota on a Sonoff motherboard and managed to do that succefully. Thereafter I connected the device to my computer using USB to initiate a serial port session for further configuration.

Both "screen" and "cu" connects to the device as I can see the output from the motherboard but I am unable to type anything on the console for both screen and cu.

Any pointers on what I might be doing wrong here?
Thanks.

gentoo_ram · Posted: Tue Feb 09, 2021 6:00 pm Post subject:

I've had some simple devices that don't implement XON/XOFF which could cause issues. Also, you will want to make sure your character setting is correct. Is it 7-Bit? Is it 8-bit? Parity?

If it's 8-bit, try this:

screen /dev/ttyUSB0 115200,cs8,-ixon

Replace the 115200 with whatever baud rate you need.

NeddySeagoon · Posted: Tue Feb 09, 2021 8:44 pm Post subject:

pankaj13,

Disconnect the USB to serial pert converter from the Sonoff motherboard and connect its Tx and Rx wires together.

That's a loopback test. The serial port setting don't matter much as the PC can not support split baud rates.
8 bit, no parity, 1 stop bit is traditional. That's written 8n1.

If the loopback test fails, your converter is probably faulty.

Are you expecting the Sonoff motherboard to echo what you type?
No all systems do that. You need to enable local echo if yours does not.

minicom is a nice serial port terminal.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

pankaj13 · n00b Joined: 05 Sep 2019 Posts: 29

@gentoo_ram & @NeddySeagoon

Thanks for your input and suggestions, let me try these options and revert back.

Since things were not working for me with serial port, I used a Windows machine and moved on but I have several more devices and would prefer not to have to switch to Windows machine for flashing and configuring these motherboard.

pankaj13 · n00b Joined: 05 Sep 2019 Posts: 29

NeddySeagoon · Posted: Wed Feb 10, 2021 10:28 am Post subject:

The loopback test does what it says.

Everything going out of the Tx pin comes back on the Rx pin. You see whatever you type. If you have local echo on, you see it twice. Once due to the local echo and once due to the serial port working, sending and receiving characters.

Until loopback works, nothing else matters.

The signal is either 3.3v or 5v. Sowe bare wire connecting the Tx and RX pins is good enough.
A few rare people can feel 5v.

Is the Sonoff supposed to echo what it receives?
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.