Are you sure everything is hooked up right?
PIC18 + GPS Help
- 27th November 2009 03:27 AM #1Toonzaka
PIC18 + GPS Help
Hello, I recently purchased a Garmin 18x LVC GPS unit to use with my micro controller. I am using a PIC18 with to communicate to the GPS unit and hyperterminal to see the data. Now I am running into some problems. For one, I am very new to GPS, this is actually the first time I am working with one and I have no idea if this unit is on or off because I am not receiving any data from the unit even after 5 minutes.
Now for the controller, as I said I am using a C-Stamp micro controller that uses a PIC18. I am not sure if anyone on this forum is familiar with that controller but it has its own syntax for sending/receiving info. I am using two simple lines that SHOULD receive any data from the GPS unit but it is not. I a, also using MATLAB and the C18 compiler.
I have a few questions now as well...
For the GPS Unit does anyone know if you have to initialize the system? I have been trying to send it a string of $PGRMC,0D0A which should echo back to me. I also read that I need to end each line with return and line feed and those are the corresponding hex values for that at the end.
Any help is welcome. I just need to get this working!
- 27th November 2009 03:30 AM #2birdman0_o 0
- 27th November 2009 04:00 AM #3Toonzaka
Yes, quadruple checked that. Right now I have an RS232 -> USB connection from the controller to my laptop. I also have the pins that use that connection hooked up to the GPS unit. I am thinking that maybe I cannot share the connection? Otherwise yes everything is connected correctly.
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- 27th November 2009 04:19 AM #4Pommie
You should be able to hook the GPS to your PC and see the data in hyperterminal. Most (I think all) GPS units default to outputting a position string every second and so you shouldn't have to send it any commands. To connect to a Pic you will need a MAX232 chip to invert and level shift the signal.
Mike.0
- 27th November 2009 04:35 AM #5Toonzaka
Would any old inverter do or do i need the MAX232 specifically?
0Last edited by Toonzaka; 27th November 2009 at 04:36 AM.
- 27th November 2009 04:40 AM #6Pommie
You could use Mike's method. Clicky.
Mike.0
- 27th November 2009 04:51 AM #7Toonzaka
Alright I tried connecting the GPS Directly to the RS232 cable to see if I can get anything on the hyper terminal, and there was nothing showing. I am uncertain as to what I am doing wrong...
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- 27th November 2009 05:08 AM #8birdman0_o
I don't think the GPS outputs +-12V, see mikes link.
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- 27th November 2009 05:20 AM #9Toonzaka
Does the db9f shell contain the BJT's or does one have to go out and make the circuit? Like can I go to radio shack tomorrow (oh god did I really say that when tomorrow is black friday!?!?) and buy one so then I can hook it up and have it working successfully? Also will a simple amp be good enough to boost the signal? I believe that the GPS outputs 5V.
Sorry for the stupid questions but like I said I am a programmer kinda guy, worked a little bit with circuitry so I know how to wire something up but when it comes to specifics... Well they just don't teach that that much in school
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- 27th November 2009 05:39 AM #10birdman0_o
You will need to get the BJT's (i think they are mosfets from the schematic) and i doubt radio shack will have that part number, worth a try though.
Or you could just use a max232 if you came across it and all the right parts.0
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