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Author Topic: COM1 Issue  (Read 559 times)
W5UV
Member

Posts: 19




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« on: January 23, 2009, 06:58:28 PM »

I have an unusual problem that has me baffled.  I am using a Dell Laptop with XP Pro.  The laptop has one serial port and one USB port (challenging to say the least!).  In my vehicle I am running a Kenwood TS-B2000 using the RC-2000 remote head.  When I connect the laptop to the radio (using com 1), I am unable to turn the radio on using the remote head (I can reach back and turn the radio on at the switch on the front of the box and all of the other functions of the RC-2000 work just fine).  However if I have a CAT program running when I try to turn the rig on, no problems! I used this exact same laptop and cables with a TS-480 and have no problems at all.  I decided to try to use a USB/Serial adapter and use a different com port, and no problem turning the rig on or off - with or without a CAT program running. Seems that there is something about com 1.  I have tried to change about every adjustment to com 1 but nothing seems to help.  Any ideas what might be causing this issue??  Thanks

73, Dennis W5UV
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KB1NXE
Member

Posts: 363




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« Reply #1 on: January 28, 2009, 08:27:44 AM »

It could be COM1 - being a native port on the PC - may be pulling one of the lines to ground while not in use (like Clear to Send [CTS]).  This may be shared with the internal logic as the 'ground to turn off' signal.  When you activate software, the pin is pulled and held high.

Through the USB <-> Serial adapter, this condition does not exist.  Different hardware, different result.

All of this is conjecture, and would take some testing and pouring through the rig's software and schematics to verify.  But it makes sense (I've been working in the computer field for 33 years and the current job that pays for Radios is Senior Network Engineer for the 10th largest private company in the US).  

If you want to dig into this, you'd need a logic probe or Break out Box with line status indicators to see state changes of the various control lines.  Then observe the states of those control lines before and after software activation.  After that, you could experiment with lifting those lines (if using the BoB) to see what condition changes the fault you are observing.

Or, you could replace the cable with a 3 wire cable (TXD, RXD and GND) between the rig and PC.  Might also resolve the issue.
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W5UV
Member

Posts: 19




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« Reply #2 on: January 28, 2009, 09:07:10 AM »

Thanks Jim.  That is what I suspect as well.  Your idea of the custom cable between the rig and the pc is probably more in line with my expertise.  I may give that a try and see if it does the trick.  I appreciate your sage advice!

73, Dennis W5UV
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AA4PB
Member

Posts: 12992




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« Reply #3 on: January 28, 2009, 03:53:15 PM »

I expect the computer is deactivating the DTR (Data Terminal Ready) pin when no programs are accessing the port.
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