dgadee
Well-Known Member
GPS puck getting a signal but GX2100 vhf isn't getting that input (I think). Three wires go from/to radio and it was all working yesterday. Is there some way to tell if there is a signal going to the VHF on those wires?
Is there an NMEA signal on my wires?
- Thread starter dgadee
- Start date
prv
Well-Known Member
Yes, if you have a PC with a serial port (or more likely nowadays, a serial to USB adapter). Connect the transmit (from the GPS) line to pin 2 and the ground line to pin 5, then open the serial port in some terminal program.
I just do screen /dev/ttyUSB0 9600 , but I imagine someone will come along shortly with a Windows equivalent.
You should then see NMEA sentences, probably three or four of them in a burst every second.
Pete
I just do screen /dev/ttyUSB0 9600 , but I imagine someone will come along shortly with a Windows equivalent.
You should then see NMEA sentences, probably three or four of them in a burst every second.
Pete
rogerthebodger
Well-Known Member
A breakout box is what I use.
Or I connect it to my PC using Navmonpc that gas an NMEA message display function and a GPS position display.
Or I connect it to my PC using Navmonpc that gas an NMEA message display function and a GPS position display.
prv
Well-Known Member
Do you just look for flashes on the RxD LED to see that "something" is happening?
Once it's connected to a PC, dedicated software like Navmonpc might be convenient if you already have it, but it's not necessary just to see if data is being received. NMEA0183 is just text, you can see it in any simple tool that can open the serial port.
Pete
Once it's connected to a PC, dedicated software like Navmonpc might be convenient if you already have it, but it's not necessary just to see if data is being received. NMEA0183 is just text, you can see it in any simple tool that can open the serial port.
Pete
rogerthebodger
Well-Known Member
Yes the LED will flash if signals are found.
I built one that also looks to the + and - voltage signals and over +3 and -3. Just remembered I had 1 red and one green for the different voltage levels. Of cause not all devices are true RS 232 and also NMEA is more like RS 422 if I remember correctly.
Any terminal emulator can be used to read what comes in the RS232 once you get the speed correct.
NMEA GPS will mainly be 4800 bps but a we know AIS is 38400 bps
dgadee
Well-Known Member
Just remembered I have a spare one of Angus' YAPPs (which may be the problem). I will change it over and then look at the NMEA - don't have a pc on that boat. Thanks for the suggestions.
Rocksteadee
Well-Known Member
Easy quick check if there is an output
Volt meter, 3.5 to 4 volt dc flash every few seconds
Volt meter, 3.5 to 4 volt dc flash every few seconds
oldgit
Well-Known Member
rogerthebodger
Well-Known Member
Here a diagram of a basic RS232 display box.
You dont need all the pins connected its really only the Tx and Rx pin you need
You dont need all the pins connected its really only the Tx and Rx pin you need
Refueler
Well-Known Member
A breakout box is what I use.
Or I connect it to my PC using Navmonpc that gas an NMEA message display function and a GPS position display.
Seaclear a simple Charting program has full IN / Out NMEA sentence display ... free to download.
Problem with Terminal progs - windows since 95 - is not so easy ... the old DOS terminal progs were simple .. Yes I come from that era !!
Refueler
Well-Known Member
Tried that years ago ... signal is so low power - never saw any results ..
Refueler
Well-Known Member
Here a diagram of a basic RS232 display box.
You dont need all the pins connected its really only the Tx and Rx pin you need
Even RS232 and NMEA need a common ground. I used to wire up 'gps' feed networks on pals boats after they saw my use of 'telephone' plugs / sockets and multiwire cables.
rogerthebodger
Well-Known Member
Windows dos not like RS232 that why i recommended NavmonPC whih is also free download and like Seaclear can display incoming messages.
rogerthebodger
Well-Known Member
Pin 5 is the RS232 signal ground an a DB9 plug top pin on upper connectors.
On a DB25 if i remember it's pin 20
prv
Well-Known Member
So why can those programs display RS232 (ish) traffic but a terminal program can't?
Pete
noelex
Well-Known Member
A good digital multimeter will show the voltage pulse. About +3v to 0 or slightly minus is typical.
A fault, or no signal transmission will give a steady state voltage. A steady +3v often indicates a device is connected, but not transmitting any data.
A fault, or no signal transmission will give a steady state voltage. A steady +3v often indicates a device is connected, but not transmitting any data.
Refueler
Well-Known Member
As a person who grew up with BBS ... DOS ... Terminal ... etc. - I can support RS comment.
When Windows displays NMEA sentences via TERMINAL based on RS232 communication ... notice the screen it is displayed on ... it is usually the DOS emulator screen that Windows uses when such is called.
Its usually easier to use a GPS Plotter program to do all that for you ....
Refueler
Well-Known Member
I am not saying you are wrong ... but when I tried in past to test signal - I have had no indication on any meter digital or other. The NMEA signal itself is so weak that it does not register.
If you are saying RS232 ... then that is a different ball game as that has a definite voltage and has to comply with the No-Damage requirement of the RS232 standards.
rogerthebodger
Well-Known Member
A terminal program can display incoming ASCII data
Not sure if windows still includes a ASCII terminal emulator.
I wrote a VT100 terminal emulator back under Dos 3.? when I used to tight in 8088 assembler, but never used one under windows 7 and above.
Sometimes I would select DOS mode under early windows and use my VT100 but non since most PC's did not have RS232 s standard and I used to address the port directly as the DOS did not any any interrupt control for thee RS232.
Do you have a user friendly terminal emulator running under windows 10 reading a standard RS232 port.