Reading PNA serial port - bytes are mixed?!

Question

0.00/5 (No votes)

See more:

VS2005

Hi everyone!

I'm working on a programme which uses the GPS data of my LG LN550 PNA.
I'm programming in VS2005 C++, and I've written my own serial handling functions, they work great,I've tested them.
But there's some problem. I can read about 1.7 kbytes of data from the serial port, looks like:

$GPRMC,223231.000,A,4708.0453,N,01926.0728,E,0.13,6.56,180710,,,A*6D

$GPGSA,A,2,11,03,19,,,,,,,,,,5.1,5.0,1.0*38

$GPRMC,223232.000,A,4708.0456,N,01926.0721,E,0.60,21.11,180710,,,A*50

$GPGSA,A,2,11,03,19,,,,,,,,,,5.1,5.0,1.0*38

$GPRMC,223233.000,A,4708.0461,N,01926.0715,E,0.00,,180710,,,A*79

$GPGGA,223234.000,4708.0461,N,01926.0715,E,1,03,5.0,44.0,M,40.7,M,,0000*68

That's good. I'm happy. BUT! After a few seconds, I receive:

GRC232.0,,7807,,12.71E00,101,,*9
GGAA21,91,,,,,3534103
$PM,23500A40.37N09602,,.0,870,A7
$PG,2360040.37N09602,,,3344.,,07M,006
$PS,,,11,6,,,,,.,.,.*C
GGV311,96,9,20,611,46,6,2,007*0
GGV321,65,6,1,712,82,5,71,1233*9
GGV331,20,1,82,608,60,9,92,534*E
GRC232.0,,7807,,12.71E00,101,,*B

You see, the NMEA sentences are totally mixed. If I close, and then open the port, it works for a few more seconds, but then it fails again. Closing and then opening the port all the time is not so good for me, because I need the GPRMC data in every second.
Any ideas?
Could anyone help me out of this problem?
Thank you very much!

Regards,
matu91

Posted 18-Jul-10 23:02pm

matu91

Add a Solution

Comments

Richard MacCutchan 20-Jul-10 9:02am

Closing and opening the port suggests it is resetting something in your code. Check your code a little more closely to see how you are dealing with the characters as they arrive.

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Alain Rist · Answer 1 · 2010-07-19T19:04:00

Solution 2

I've written my own serial handling functions, they work great,I've tested them.

Hmm, they don't seem to work that well :)

You need a listener thread filling some buffer with the incoming characters and signalling the main thread when a full sentence is ready.
The main thread should then read the sentence and restart or wake up the listener.

cheers,
AR

Posted 19-Jul-10 19:04pm

Alain Rist

Comments

matu91 9-Aug-10 12:00pm

Actually, I've tested them on PC. I write my programme both for PC and PNA, and when the PC version works, I write the PNA version, too.
Thanks for your answer, but it didn't help me. The results that I've copied here were made by my test programme, which writes the received characters immediately into a text file. So something else can be the problem. Maybe SirfStarIII internal buffer problem, or what? I have absolutely no idea what can be the problem. iGo works, my prog doesn't. :)

Alain Rist 10-Aug-10 2:09am

Unfortunately the IO routines are handled differently by WinCE and Windows. Check your device SDK IO support (it's not a Windows Mobile device and should have a matching SDK).
On a WinMobile 5 smartphone, I got that working with a reader thread reading 1 char at time until '$' signalling then a listener thread which would store the sentence post a message to the app main window, reset the read buffer and restart the reader thread. Worked OK for hours or days.
cheers