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Serial port = lack of hair!

David_W
Rising Star
Posts: 2,293
Thanks: 29
Registered: 19-07-2007

Serial port = lack of hair!

My PC doesn't have a serial port, nor does my laptop so to get my console cable for my Cisco working I needed an adapter which I have, a USB to RS232 adapter, that is plugged in to my USB port at 9,600, 8, N, 1, None.  So far so good, I plug in the Cisco serial>console cable into the serial side and the console side, fire up putty and nothing, so I figure it's Windows 7.
I reboot into Ubuntu and download cutemon (I liked the name) and gtkterm, Ubuntu finds the device as a Prolific PL-2303 (though I believe it's the 2303X) and assigns it to ttyUSB0 so in cutemon/gtkterm/putty I connect to ttyUSB0 and the result is either garbled nonsense (gtkterm) or 0x00 (cutemon).  I'm pulling my hair out in frustration, I want to get my Cisco 857w working but DCHP isn't on so it won't assign an IP address and forcing it with the gateway at 10.10.10.1 or 10.0.0.1 or 192.168.0.1 or 192.168.10.1 doesn't let me log in to the router (assuming of course that HTTPD is on).
So, can anyone think of a reason why I'd get 0x00 from cutemon, putty shows nothing (or maybe a lot of pppppppp's) and I'm basically unable to connect to the router via the console cable?
9 REPLIES
Community Veteran
Posts: 6,607
Thanks: 209
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Registered: 16-02-2009

Re: Serial port = lack of hair!

Sounds like wrong baud rate or handshake issues, does it need hardware h/s or xon on none?
David_W
Rising Star
Posts: 2,293
Thanks: 29
Registered: 19-07-2007

Re: Serial port = lack of hair!

The Cisco *should* be 9,600, 8 data bits, no parity, 1 stop bits, no flow control (which is what I've set it up to).  I've tried every possible speed cutemon offered to no avail.  I've been at it since about 2pm, so yeah, I really wish I had a serial port right now.
Community Veteran
Posts: 5,472
Thanks: 288
Fixes: 4
Registered: 11-08-2007

Re: Serial port = lack of hair!

Try doing this on the RS232 connector on your adaptor - WITHOUT the Cisco plugged in.
Connect your RS232 terminal adaptor.
Run your RS232 terminal emulator program and run it in VT100 mode if possible.
Type a few characters, and see if anything is echoed to the screen.
Connect the RS232 "TX" to "RX"  together (usually pins 2 and 3) - easy to do with a metal screwdriver !.
Type some more characters and see if the echoed characters have changed.
This test will check if you can at least transmit something, by effectively listening to your own output.
If that fails then you might not be transmitting because of hardware handshaking.
This time wire the RTS and CTS lines together (pins depend on connector type ! - so you need your handbook)
Repeat the previous TX/RX test.
Hopefully now your TX has been unblocked.
You need to get to a point where you are getting exactly one correct echo for every character typed - BEFORE connecting the Cisco
Good luck
David_W
Rising Star
Posts: 2,293
Thanks: 29
Registered: 19-07-2007

Re: Serial port = lack of hair!

Unplugged from the Cisco I fired up putty, started a session and couldn't type anything, a blank screen so I guess the adapter is faulty?
Community Veteran
Posts: 5,472
Thanks: 288
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Registered: 11-08-2007

Re: Serial port = lack of hair!

Have you tried a different software terminal program ?
I used to use "HyperTerminal" for this sort of RS232 work.
You should be able to download the latest free 30 day trial version, from a simple google.
I don't know about Windows-7, but Windows-XP used to come with an ancient version of "HyperTerminal" (start->Accessories->Communications->),  I seem to remember form years ago that this version was not that great (but I was doing major RS232 debugging) - but if it is already on your machine, then it might be enough to get you going.
David_W
Rising Star
Posts: 2,293
Thanks: 29
Registered: 19-07-2007

Re: Serial port = lack of hair!

I've tried Hpyerterminal, cutemon, gktterm and putty.
With nothing plugged in I get no response, if I plug in the console cable with the Cisco turned off, no response, if I turn on the Cisco I get \0x00 so something is being fed to the device?  Well, there is lot's of traffic now but it's all jibberish.  It's not as though I have any other serial device to check if it's the serial cable either.
So, there does seem to be traffic coming from my router but somewhere along the line it's being corrupted, could it be the serial side is miswired?
/edit - in a terminal window I typed cp /dev/ttyUSB0 /dev/tty which outputs the result of ttyUSB0 apparently, and in a new terminal window typed echo test_message > /dev/ttyUSB0 which *should* have displayed it on terminal window 1, but that remained blank.
Community Veteran
Posts: 6,607
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Registered: 16-02-2009

Re: Serial port = lack of hair!

Have you bridged the tx/rx lines this is needed for a test like this. (pin 2+3 on the serial connector, a crocodile clip or similar between them)
Check the settings for handshaking settings as well.
Do you have an old serial modem lying around that would be best to test it on?
Community Veteran
Posts: 5,472
Thanks: 288
Fixes: 4
Registered: 11-08-2007

Re: Serial port = lack of hair!

Have you installed the Windows-7 driver as per the instructions here - http://www.prolific.com.tw/support/files/%5CIO%20Cable%5CPL-2303%5CDoc%5CUser%20Manual%5Cum_pl2303_D...
David_W
Rising Star
Posts: 2,293
Thanks: 29
Registered: 19-07-2007

Re: Serial port = lack of hair!

Aye, with 2_3 shorted I still can't input any characters in Hyperterminal.
I've installed the Win7 drivers but not the latest, the latest give me a silly Cannot start 10 error so I have to use 1.20 rather than 1.30, Linux though the drivers are built into the kernel now.
/edit - I've ordered a Belkin USB to Serial which uses the same chipset (joy!) but is a "branded" product, and got a refund on the faulty one.  It was either that or make my own serial cable and plug it into the headers on my motherboard which would have resulted in a whole new "oh, I broke my motherboard..." thread  Crazy