GPS with microcontroller

hayee · Joined: 05 Sep 2007 Posts: 252

Hi,
Have anyone use GPS module (GT-310FA) with pic16f877a.
I want to send some instruction to the module and read time/date from the module.
Can anyone have idea how to do this?

bkamen · Posted: Fri Oct 16, 2009 9:35 am

I implemented a GPS2058 from DeLorme... Works great.

The GPS is the system clock source for the RTC. Once the RTC is set, the GPS is turned off.

I did my routine using a UART ISR that collects the string and on CR/LF parses it out.

Works great.

--- Additional:

Make sure you use a hardware UART for the GPS. Don't try to do any RS232 in software.

If you need more than 1 UART, get a PIC with 2 UARTs. The 18FxxJ11 series is the way to go for low pin-counts.

I used an 18F46J11 on a project recently and it's worked out nicely so far.
_________________
Dazed and confused? I don't think so. Just "plain lost" will do. :D

hayee · Joined: 05 Sep 2007 Posts: 252

Can anyone give me some c code examples how to send and receive data from GPS (specially for GT-310FA).

bkamen · Posted: Sat Oct 17, 2009 8:34 am

I'll PM my code for the DeLorme unit to you later -- just please don't redistribute. Have people come to me for a copy.

I'm just about to run out on some errands and then I'll be back.

I also used the same code slightly modified for a Garmin OEM GPS/16x.

All GPS's although NMEA will be a little different (shame on them! Goodbye standards).. but it's not hard to modify for your GPS.

-Ben
_________________
Dazed and confused? I don't think so. Just "plain lost" will do. :D

hayee · Joined: 05 Sep 2007 Posts: 252

Thanks bkamen.

I am getting RMC data on my hyper terminal like this:
-------------------------------------------------------------------------------------
$GPRMC,160612.00,A,2456.4010,N,06705.1067,E,000.1,083.8,191009,000.4,E,A*35
$GPRMC,160613.00,A,2456.4011,N,06705.1065,E,000.1,083.8,191009,000.4,E,A*37
$GPRMC,160614.00,A,2456.4012,N,06705.1063,E,000.1,083.8,191009,000.4,E,A*35
$GPRMC,160615.00,A,2456.4013,N,06705.1061,E,000.1,083.8,191009,000.4,E,A*37
$GPRMC,160616.00,A,2456.4013,N,06705.1060,E,000.0,083.8,191009,000.4,E,A*34
$GPRMC,160617.00,A,2456.4013,N,06705.1058,E,000.0,083.8,191009,000.4,E,A*3E
$GPRMC,160618.00,A,2456.4013,N,06705.1056,E,000.1,083.8,191009,000.4,E,A*3E
$GPRMC,160619.00,A,2456.4013,N,06705.1053,E,000.2,083.8,191009,000.4,E,A*39
$GPRMC,160620.00,A,2456.4013,N,06705.1050,E,000.1,083.8,191009,000.4,E,A*33
$GPRMC,160621.00,A,2456.4016,N,06705.1047,E,000.1,083.8,191009,000.4,E,A*31
$GPRMC,160622.00,A,2456.4016,N,06705.1045,E,000.1,083.8,191009,000.4,E,A*30
$GPRMC,160623.00,A,2456.4016,N,06705.1042,E,000.1,083.8,191009,000.4,E,A*36
-------------------------------------------------------------------------------------

Now I want to read that data in microcontroller and display it on the LCD.
Can anyone tell me how to do it

bkamen · Posted: Mon Oct 19, 2009 9:31 am

If you'll notice, the GPS information is stored in a structure of strings and variables.

You need to decide what you want to print but essentially you would have a line that says

printf(lcd_putc,"%s", string);
or
printf(lcd_putc,"%u or %c", variable, character);

Have fun!

-Ben
_________________
Dazed and confused? I don't think so. Just "plain lost" will do. :D

hayee · Joined: 05 Sep 2007 Posts: 252

Thanks bkamen,
In this sentence there are strings, integers and floating numbers are present. You may find this as a silly question but I don't know how to get all these data and what type of buffers are used to store it.
Can you generate a code for me?

bkamen · Posted: Tue Oct 20, 2009 5:49 pm

hayee · Joined: 05 Sep 2007 Posts: 252

bkamen I didn't see your code. That's why I reply. I got your code and seeing how you done it.
Anyways thanks alot for your cooperation.

hayee · Joined: 05 Sep 2007 Posts: 252

I saw your code. Can I read data without using interrupt?
I don't wanna use interrupt.

bkamen · Posted: Wed Oct 21, 2009 6:02 am

the interrupts are really nice..

while I suppose you could do it without, if your project has any other tasks going on, this would make everything run more consistently rather than stalling out "polling" for GPS sentences.

Why don't you want to use interrupts?

-ben
_________________
Dazed and confused? I don't think so. Just "plain lost" will do. :D

hayee · Joined: 05 Sep 2007 Posts: 252

You are right I have another tasks, I am also using two more interrupts(External).
Can you explain in wordings about the steps required in reading the data from GPS module.
I have found a code by searching the forum. Will this code work? This code is using GPGGA format. I ran it by doing some changes according but it is not working. Original code is as follows.
http://www.ccsinfo.com/forum/viewtopic.php?t=36043

hayee · Joined: 05 Sep 2007 Posts: 252

Thanks bkamen.
I understand the RDA interrupt service routine and implement it and got the data in the microcontroller from GPS module without any error.
It is displaying on hyper terminal and on LCD.
Now the remaining part is that I have to separate time and date from the received sentence, and display it on the LCD.
Can you help me how to convert these data's in integer format because right now data is in string format.

bkamen · Posted: Sat Oct 24, 2009 11:40 am

hayee · Joined: 05 Sep 2007 Posts: 252

Ya I have to separate the time and date because I will use time and date parameter in my program to store some data according to time and date.
In the time I only want (hhmmss) only not the remaining (.ss) part so I think I have to use atoi() function instead of atof().
I am doing like this way in my code