[Dclug] USB Serial Port Problem

[Zebrowski, Zak]

FWIW - Another random shot in the dark - try an intermediate level solution like ser2net which is an application that allows you to "telnet" into a device.  You can specifiy some  connection options in /etc/ser2net.conf ...

From: dclug-bounces at calypso.tux.org [mailto:dclug-bounces at calypso.tux.org] On Behalf Of James Ewing Cottrell 3rd
Sent: Thursday, July 08, 2010 4:13 PM
To: David C Niemi
Cc: 'dclug at tux.org'
Subject: Re: [Dclug] USB Serial Port Problem

It all depends on what the device wants, but serial communication is typically 10 bits...one start bit (a space), 8 data (low bit first), and one stop bit (mark). Sounds like your first stop bit is being treated as the 8th bit and will be seen as a one. Most devices either want a specific parity (odd or even), but many will take space parity. Mark parity means that the device will specifically have to ignore the high bit. You may be feeding the device characters it doesn't know about, and it it is streaming them, you may get framing errors.

JIM

Two stop bits are used on 110 baud, but nowhere else that I know of.

One possibility is that you might want to do something like "sleep 99999 < /dev/ttyxx" just to keep the device open. It's not clear that you aren't resetting it between characters, altho that's a longshot.

On 6/19/2010 4:21 PM, David C Niemi wrote:

On Sat, 19 Jun 2010, Klosowski, Przemek wrote:





It is possible that the Problem is that the port is too fast eg shooting

characters back to back instead one char at a time perhaps in the old

driver. I have seen simple serial ports getting confused by such fast

incoming data--i think they couldn't synch to start bit immediately

following a stop bit w/o mark space delay. To check this try outputing

one char at a time maybe even with few ms delay





I'm only sending an occasional carriage return at 1200 baud, 7 bits, 2

stop bits.



Another change, I think, is that there is a second delay after every

character sent, but it's possible that was always the case.



+-----------------------------------------------------------+

| David C Niemi  (Reston, VA, USA)  niemi at tuxers dot net |

+-----------------------------------------------------------+

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