Re: Serial (RS232) communication - failing to detect stop bit

OK...

I have come to the conclusion that there is something fishy about the
serial driver in Gentoo. Below I describe the tests that led me to
this conclusion.


I conducted a series of chat tests between 2 machines, PC-1 and PC-2,
using terminal software on both machines and connected the serial
ports of the PCs using an RS232 cross cable (this may be called a NULL
modem cable in some regions).

PC-1 has Gentoo Linux installed. PC-2 has 3 partitions: Windows XP,
Windows 2000, and Xandros Linux.

The terminal software used was Minicom on Gentoo, and HyperTerminal on
Windows.

The connection settings on both sides were as follows.
-------------------
Bit rate: 9600
Data size: 8 bit
Parity: none
Stop bits: 1
Flow control: none

In short form: 9600, 8N1
-------------------

I tested to see if text typed in the terminal of one machine properly
showed up in the other machine or not. I also made use of the
following Linux (Unix) command to view the number of bytes sent (tx)
and received (rx):
# cat /proc/tty/driver/serial


Here are my test results

(1) Gentoo Linux and Windows XP
PC-1: Ran Gentoo Linux off HDD, used Minicom
PC-2: Ran Windows XP off HDD partition, used HyperTerminal

Results:
FAILURE :(
Text typed on PC-1 is correctly displayed on PC-2. However text typed
on PC-2 is NOT displayed on PC-1.
Using # cat /proc/tty/driver/serial on PC-1, I could see that the
number of received bytes was increasing correctly. So the bytes from
PC-2 are being received, just not showing up in Minicom.


(2) Gentoo Linux and Windows 2000
PC-1: Ran Gentoo Linux off HDD, used Minicom
PC-2: Ran Windows 2000 off HDD partition, used HyperTerminal

Results:
FAILURE :(
Exactly the same results as in test (1).


(3) Gentoo Linux and Xandros Linux
PC-1: Ran Gentoo Linux off HDD, used Minicom
PC-2: Ran Xandros Linux off HDD partition, used Minicom

Results:
FAILURE :(
Exactly the same results as in test (1).


.... Now at this point, if you are starting to suspect a hardware issue
on PC-1, this is where things get interesting and I prove this is not
the case!


(4) Knoppix Linux and Xandros Linux
PC-1: Ran Knoppix Linux off a live CD, used Minicom
PC-2: Ran Xandros Linux off HDD partition, used Minicom

Results:
SUCCESS!!! :)
Everything typed on one machine shows up in the other machine's
terminal. This indicates that the hardware on PC-1 is fine.


(5) Ubuntu Linux and Xandros Linux
PC-1: Ran Ubuntu Linux off a live CD, used Minicom
PC-2: Ran Xandros Linux off HDD partition, used Minicom

Results:
SUCCESS!!! :)
Results identical to test (4) above.


.... Now, to make sure that it is not a problem with the way I have
installed Gentoo, I used a live CD version of Gentoo from the CD
enclosed in a recent book, Linux Bible 2007 Edition, which should have
much more credibility than my own installation (since I am a newbie,
and those guys are authors). In fact, here is the book:
http://www.amazon.com/Linux-Bible-2007-KNOPPIX-Distributions/dp/0470082798/

(5) Gentoo Linux from live CD and Xandros Linux
PC-1: Ran Gentoo Linux off a live CD, used Minicom
PC-2: Ran Xandros Linux off HDD partition, used Minicom

Results:
FAILURE :(
Results identical to test (1) above. So the live CD Gentoo is
behaving the same way as my own Gentoo installation.


(6) Gentoo Linux and Windows 2000, on seperate machines at my client's
site.
FAILURE :(
I asked my client to do exactly what I did in test (2) above, using
their machines. The results were exactly the same as my test (2)
results, which further reinforce the probability that I don't have a
hardware problem and that my Gentoo installation is not the problem.


So this leaves me with the conclusion that there is something flawed
in Gentoo itself.

I am not very knowledgeable about serial drivers. I would like to
compare the serial driver versions between my Gentoo machine and my
Xandros machine (as well as the versions of the serial drivers in the
live CD Knoppix and Ubuntu). Does anyone know what specific files I
need to look at and compare?

Also, does anyone have any idea as to how I should go about solving
this problem? I need to have proper serial data receive functionality
on my Gentoo machine, since that will be used to get data from a
measuring instrument.

Thanks!


.

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