Bug#670804: Fwd: Bug#670804: Software flow control doesn't work correctly.

---------- Forwarded message ----------
From: Oscar Molin <oscarmolin@gmail.com>
Date: 2014/1/5
Subject: Re: Bug#670804: Software flow control doesn't work correctly.
To: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

Hi

Sorry but this was ages ago and I don't have access to this hardware anymore to try it. It's possible these other terminal programs had different tolerances with regards to stop bits etc and that the development board I was using at the time was actually too far out of sync in terms of baud rate. I seem to remember these MSP430s had a complicated clock system and it might have deviated too much from the baud rate used by the PC.

If you want to investigate these effects you might consider using some cheap embedded prototype board and set the clocks further and further away from the correct speed and see which terminal program stops working first.

In my use case, the data amounts were small so the xoff/xon appeared very often. Maybe they were mistaken for bits?

To clarify, the device I used was a Zolertia Z1, which is a wireless prototyping board with a MSP430 microcontroller and a rs232 to usb bridge chip, and it was connected to a PC using this usb connection.

If you think this would be an interesting line of inquiry, I actually have access to a wide range of embedded prototyping and evaluation boards for a wide range of microcontrollers as I'm now employed at an embedded compiler/ide company so I could test some devices with microcom and other terminal programs.

However I think the issue is general one so testing wouldn't really give any useful data. Microcom is/was for some reason more picky about having correct baud rate than other serial terminal programs like putty or nanocom etc.

As you probably know, these boards rarely have the special 4.13MHz(or whatever it is, it slips my mind at the moment) crystal for UART that most PCs have, so the clock used by the UART in microcontrollers usually deviate a few % from the clock in the host PC.

Best regards,
Oscar Molin

2014/1/4 Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

tags 670804 + moreinfo
thanks

Hello Oscar,

On Sun, Apr 29, 2012 at 08:46:20AM +0200, Oscar Molin wrote:
> Connecting to /dev/ttyUSB0 (CP210x) to a Zolertia Z1,
> software flow control setting doesn't work when enabled in the microcom menu.
> When typing characters into microcom, only some characters are
> received by the device at the other end.
> Equivalent settings tested in linux putty and nanocom work correctly.
With "software flow control" you mean you do "flow soft" in the microcom
menu?

Can you please provide the output of

stty -F /dev/ttyUSB0

once with microcom running with software flow control and once with
putty or nanocom. (So once with the broken state and once with the good
one.)

Best regards
Uwe