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Old 13-02-2012, 21:11   #1
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NMEA Signal Lost When Using USB to RS232 Converter

Hi,


Currently I am using an old notebook for chart plotting. NMEA Data is coming from a Garmin GPS and received by the RS 232 port of the notebook. The NMEA data is also shared with the VHF and SSB (for DSC).
I would like to upgrade the notebook but the new notebooks does not have RS 232 port.
So I bought an USB to RS232 converter.

Unfortunately the converter can not pick up the signal of the GPS. I am testing it using a terminal emulating software. It only picks up curly braces.
On the converter there is a led indicating communication and it blinks weakly.
I tried to connect the converter to my Nexus NX2 server (which acts as an NMEA repeater), it blinks strongly and I can receive the NMEA sentences. However this is not an option because through the server I cannot send routes back to the GPS.

So I bought another converter - a different brand. Same problem.

A possible solution would be an RS232 amplifier, but I would like to avoid it becuse of complexity and extra electric consumption.

I am thinking about getting an industrial grade USB to Serial converter but I am concerned that it will be expensive and it won't work anyway.

Ideas?
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Old 13-02-2012, 21:18   #2
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Re: NMEA signal lost when using USB to RS232 converter

Perhaps try a different converter?

This one is working for me on three different USB ports (three NMEA 0183 sources going into the nav computer).

Amazon.com: IOGEAR USB 2.0 to Serial/PDA Converter Cable GUC232A: Electronics

You have to go to their website and download the drivers specific to your operating system.

Your drivers are working correctly, right? You do not have a yellow markers in Device Manager?

If you have a Windows XP machine you can use Hyperterminal to troubleshoot. In Windows 7 go to Programs and Features, Turn Windows features on or off and select the Telnet Client. Or you can install Hyperterminal into Windows 7. Hilgraeve Products - Hilgraeve Or google search HTPE63.exe

You are using pins 2 (input),3 (output) and 5 (ground) on your db9 connector?
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Old 13-02-2012, 21:20   #3
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Re: NMEA signal lost when using USB to RS232 converter

Quote:
Originally Posted by rotorman View Post
Hi,


Currently I am using an old notebook for chart plotting. NMEA Data is coming from a Garmin GPS and received by the RS 232 port of the notebook. The NMEA data is also shared with the VHF and SSB (for DSC).
I would like to upgrade the notebook but the new notebooks does not have RS 232 port.
So I bought an USB to RS232 converter.

Unfortunately the converter can not pick up the signal of the GPS. I am testing it using a terminal emulating software. It only picks up curly braces.
On the converter there is a led indicating communication and it blinks weakly.
I tried to connect the converter to my Nexus NX2 server (which acts as an NMEA repeater), it blinks strongly and I can receive the NMEA sentences. However this is not an option because through the server I cannot send routes back to the GPS.

So I bought another converter - a different brand. Same problem.

A possible solution would be an RS232 amplifier, but I would like to avoid it becuse of complexity and extra electric consumption.

I am thinking about getting an industrial grade USB to Serial converter but I am concerned that it will be expensive and it won't work anyway.

Ideas?
Yes, I know a Keyspan converter will convert it if the GPS is still okay. Try to connect just the GPS to the converter, without VHF and SSB. If that does work then it might be something else in the cabling involved.

ciao!
Nick.
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Old 13-02-2012, 21:38   #4
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Re: NMEA signal lost when using USB to RS232 converter

Why dont you pick up bu353 for $28 on Amazon. Still have to use the usb to db9 to tie other things in, but it should solve your gps problems.

I use laptop with bu353 and usb to db9 for auto pilot.
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Old 13-02-2012, 22:52   #5
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Re: NMEA signal lost when using USB to RS232 converter

What operating system is the computer using? Vista and W7 left a lot of cheap converters unsupported.
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Old 14-02-2012, 09:10   #6
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Re: NMEA Signal Lost When Using USB to RS232 Converter

First and foremost, have you installed the drivers on your computer for the USB to Serial converter? Next, have you assigned whatever program you are running the correct serial port that the converter is using? Chuck
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Old 14-02-2012, 09:53   #7
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Re: NMEA Signal Lost When Using USB to RS232 Converter

An easier solution might be to change your Garmin GPS for a Garmin GPS USB reciever. Puck style.
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Old 14-02-2012, 18:10   #8
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Re: NMEA Signal Lost When Using USB to RS232 Converter

Quote:
Originally Posted by familycruisers View Post
Why dont you pick up bu353 for $28 on Amazon. Still have to use the usb to db9 to tie other things in, but it should solve your gps problems.

I use laptop with bu353 and usb to db9 for auto pilot.
Quote:
Originally Posted by Lancerbye View Post
An easier solution might be to change your Garmin GPS for a Garmin GPS USB reciever. Puck style.
I don't know what the Garmin unit costs, but I can recommend the bu353 too and report it is 100% compatible with Apple mac.

ciao!
Nick.
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Old 14-02-2012, 18:32   #9
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Re: NMEA Signal Lost When Using USB to RS232 Converter

"Curly braces" sounds like the USB driver is fine but the bit rate is set to the wrong speed, or perhaps the NMEA input is connected backwards. The proper NMEA output is balanced, with two mirror-image outputs. You need to connect the right output (usually the "+") to the serial input and then probably connect a ground to the serial ground pin. There can be difficulties when you run a balanced NMEA signal to the unbalanced RS232 input, but it usually works just fine.

The usual GPS bit rate is 4800. If that doesn't work, use the opposite NMEA outpit wire. If it still doesn't work, try setting the USB adaptor bit rate to 38400 and try again.
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Old 14-02-2012, 19:16   #10
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Re: NMEA Signal Lost When Using USB to RS232 Converter

Quote:
Originally Posted by familycruisers View Post
Why dont you pick up bu353 for $28 on Amazon. Still have to use the usb to db9 to tie other things in, but it should solve your gps problems.
I am using the Gramin handheld as a fixed GPS in the cockpit (I upload routes from the PC and then shut down the PC). So I need a handheld. But thanks for the tip.

Quote:
Originally Posted by donradcliffe View Post
What operating system is the computer using? Vista and W7 left a lot of cheap converters unsupported.
Tried both with W7 and IOS. I have converter which works with both system. I can read the NMEA signal with them through the NMEA repeater. It just does not work directly.

Quote:
Originally Posted by Paul Elliott View Post
"Curly braces" sounds like the USB driver is fine but the bit rate is set to the wrong speed, or perhaps the NMEA input is connected backwards. The proper NMEA output is balanced, with two mirror-image outputs. You need to connect the right output (usually the "+") to the serial input and then probably connect a ground to the serial ground pin. There can be difficulties when you run a balanced NMEA signal to the unbalanced RS232 input, but it usually works just fine.

The usual GPS bit rate is 4800. If that doesn't work, use the opposite NMEA outpit wire. If it still doesn't work, try setting the USB adaptor bit rate to 38400 and try again.
Thanks for the tip. The bit rate is set up fine. However maybe the wiring is connected backwards, will check tonight.
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Old 15-02-2012, 14:26   #11
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Re: NMEA Signal Lost When Using USB to RS232 Converter

Ok, found the problem.

The ground pin of the cable from the NMEA bus to the PC was only connected to the cable shield and not to the NMEA (boat) ground.
On my old PC's serial port the shield and the ground were connected so it was working. With the new PC on the serial to USB converter they are not connected.
Connecting the pin to ground solved the problem.

Thanks for all the advice!
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