[IGSTK-Developers] Loopback test

[David Gobbi]

Hi Luis,

The loopback that I have working on "beck" just has pins 2-3 shorted, it 
doesn't have any of the handshaking pins connected like you have for 
zion.  It works for me under both Linux and Windows. 

You really shouldn't be testing it by doing a "cat" to the /dev/ttyS0, 
because the state of the device is unknown unless you previously set its 
state using "tcsetattr".  It is much better to test it from within a 
terminal program, or from within a C program where you have used 
tcsetattr to put the serial port into a known state.  For instance, I 
think you see the buffering on your serial port because your serial port 
is set to "canonical" mode by default.  In canonical mode, it always 
buffers until until it receives a newline (and I suspect that the 
buffering you are seeing is on the input, not on the output -- the 
output buffer is only used when characters are sent to the serial port 
too fast for the baud rate to keep up).  The igstk::SerialCommunication 
class turns off canonical mode, so that characters can be received 
one-at-a-time instead of one line at a time.

Patrick: if you are using a Windows machine, then hyperterm is the right 
way to test the loopback.  Luis is right that, if you aren't seeing 
anything, you should try turning off flow control.  Also, to make sure 
that commands are getting out to the serial port, you can unplug the 
loopback and plug in an AURORA or POLARIS.  Then, if you do "INIT 
"<carriage return> "BEEP 2"<carriage return> it should beep for you.  If 
commands can get out to the AURORA but not back in through the loopback, 
you know the loopback has problems.

On my side, I'll make another loopback with the extra pins connected so 
that I can see what kind of different behavior it has compared to my 
single-wire loopback.

 - David

Luis Ibanez wrote:
> Hi Patrick,
>
> Here is the wiring that I'm using in
> the Loopback device installed in Zion:
>
> a)  1====4====6
> b)  2====3
> c)  7====8
>
> This looks the same as the one that you posted
> in your email.
>
> In  Linux we tested the device by just opening
> two terminals and doing:
>
>      a)   cat  /dev/ttyS0  (in one terminal)
>      b)   ls -R  /  > /dev/ttyS0  (on the other terminal)
>
> You should see text appearing in the first terminal.
>
>
> Notice that since the serial port is buffered, you may
> not see any output if you just send a couple of words.
> You may have to send more that some Kb of text to make
> sure that the serial port buffer if flushed and you
> actually see something in the other side.
>
> This being said. The IGSTK test is failing in Zion,
> and we have never been able to connect to the Polaris
> from the Linux machine.
>
> I just tested the same device on my Windows laptop,
> using the Hyperterminal test that you posted, and it
> works fine for me. That is, when the loopback device
> is connected, I see the text that I'm typing, and
> when the device is remove, I don't see the text that
> I'm typing.
>
> Did you selected "Flow control" to "None"  ??
>
>
>
>    Luis
>
>
>
> ---------------------
> Patrick Cheng wrote:
>> Hi everyone,
>>
>> I just made a loopback device and plug it into the windows machine 
>> here, and it turned out that the SerialCommunicationTest failed too.
>> http://public.kitware.com/IGSTK/Sites/build02.isis/Win32-IGSTK-VS71-Debug-Loopback/20060310-0430-Nightly/Test.html 
>>
>>
>> I followed the wiring instruction in the attached picture. and I try 
>> to use a windows program to test if this loopback device is working.
>>
>> Start -> All Programs -> Accessories -> Communications -> Hyper Terminal
>>
>> I followed the test under this link:
>> http://zone.ni.com/devzone/conceptd.nsf/webmain/D48BA43C59B60277862569EE000501FD 
>>
>>
>> Quote, "You will see the terminal window as shown below. If your 
>> serial port is working and the loopback cable is properly connected, 
>> the text you type appears in the window. If you remove the cable and 
>> type text, it should not appear in this window. If this test behaves 
>> differently than described here, see the troubleshooting advice at 
>> the end of this section. "
>>
>> I don't see the text when I am typing, so I guess the loopback is not 
>> being set up correctly, I don't know if this is the same situation on 
>> Zion-Loopback machine.
>>
>> Am I doing the wring right? or it's a contact miss problem?
>>
>> Patrick
>>
>> ------------------------------------------------------------------------
>>
>>
>> ------------------------------------------------------------------------
>>
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