 Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me. |
Forum Index : Microcontroller and PC projects : GPS
Page 1 of 2   |
|||||
| Author | Message | ||||
| devigan Newbie  Joined: 11/08/2011 Location: AustraliaPosts: 26 |
Hi Guys, can anyone guide me with GPS interface and read and log to SD. Daven |
||||
Keith @ Senior Member  Joined: 19/06/2011 Location: AustraliaPosts: 167 |
Daven try this Microchip article as a starter ww1.microchip.com/downloads/en/AppNotes/01373A.pdf Keith The more we know, the more we know we don't know ! |
||||
| Keith @ Senior Member Joined: 19/06/2011 Location: AustraliaPosts: 167 |
Daven delete the back shed prefix from the URL when you get the 404 error Keith The more we know, the more we know we don't know ! |
||||
| devigan Newbie Joined: 11/08/2011 Location: AustraliaPosts: 26 |
thanks |
||||
| devigan Newbie Joined: 11/08/2011 Location: AustraliaPosts: 26 |
Hi guys, just got 2.5c working with the GPS, although I can see GPS data on buddy. Can someone help me with the code to extract Lat Long. Dave |
||||
| Talbit Senior Member Joined: 07/06/2011 Location: AustraliaPosts: 210 |
Dave, I need to do exactly the same. I was waiting for Geoff's serial to be completed. I'm OS at the moment. I haven't got my MM with me or any of my notes but it's a fairly easy task to "Parse" ie extract the info from the NMEA string. I've gone part the way but won't attempt a solution for you until I get back home and check my notes. Hopefully someone will have a heap of solutions for you soon and I'll be keen to see what they come up with. What do you mean by buddy? Trevor Talbit |
||||
| devigan Newbie Joined: 11/08/2011 Location: AustraliaPosts: 26 |
sorry what I meant was putty terminal |
||||
| Talbit Senior Member Joined: 07/06/2011 Location: AustraliaPosts: 210 |
Dave, I see no one has answered your request so I'll have a go from memory. First I assume your NMEA string looks something like this... $GGAXXXXXXXX22.1462S,196.8194EXXXXX First thing is to make it a string by saying something like String$="$GGAXXXXXXXX22.1462S,196.8194EXXXXX" Then you do something like LAT$=MID$(13, 8) The 13 is the position of the first LATITUDE character (2) and you select 8 characters. LAT$ should then be equal to 22.1462S You do the same for the LONGITUDE LONG$=MID$(22, 9) LONG$ should then be equal to 196.8194E Remember, I'm going by memory! Hopefully someone will come alone and clean up my attempt! Regards Trevor Talbit |
||||
sparkey Senior Member Joined: 15/06/2011 Location: AustraliaPosts: 819 |
there is better hex code avaliable go to the 2,5c thread and get an update of 2.5"f" its better than "c" regards sparkey its link is on page 8 of the maxi 2.5c i/o thread 2.5f.zip technicians do it with least resistance |
||||
| devigan Newbie Joined: 11/08/2011 Location: AustraliaPosts: 26 |
Hi guys, I have 2.5f loaded. But my problem to how do you grap the String$="$GGAXXXXXXXX22.1462S,196.8194EXXXXX" from all sentence the GPS is spitting out every hz. Dave |
||||
| sparkey Senior Member Joined: 15/06/2011 Location: AustraliaPosts: 819 |
find a data logging program you might try silicon chip web site or if you have some older sil chip mags u may find something there you might have to wait till otheres get back tonite they may have some ideas for you,...regards sparkey technicians do it with least resistance |
||||
trippyben Regular Member  Joined: 26/06/2011 Location: AustraliaPosts: 91 |
I've only done it in assembly and C, but here's (basically) the steps I took. Use interrupts to trigger each time a character is received. 1) Sample and store each character in an array 2) When the $ character is found, reset the array pointer. 3) The NEMA strings are terminated by a CR and LF character. Detect either one, or both (whatever suits) and signal to external routines that the array is full and ready to be sampled. The main routine can loop around doing what ever is needed. When the array full flag is set, it can check the data in the array. 1) Test data string by comparing the GPGGA, GPGSV etc. 2) If the required string is in, further process the array. Be aware that the length of each string will vary depending on the sat lock status and that character counting functions won't work correctly as a result. The comma characters are place holders and are always present in the string even if the data between is missing. A more relaible way of getting the data you want is to count commas and then sample the data you need, terminated by the next comma. It may also be eaiser to turn off the unsued output strings during GPS module initialisation. There's a few on-line NEMA string checksum calcuators to help with getting the required checksum for your desired command string. 2011-09-06_203340_NMEA_commands.pdf |
||||
| devigan Newbie Joined: 11/08/2011 Location: AustraliaPosts: 26 |
Thanks for the info Trippy, Any progress with your GPS Project talbit. I am still at the gate. The GPS spits out data on the Console mode but nothing in the program mode. ie I hope to see something in the terminal but it is blank 100 OPEN "COM1:4800" AS #5 200 Print #5 "$PSRF103,4,0,1,1*21" ; 300 Data$ = Input$(50, #5) 400 Print Data$ 500 Data$ = "" 600 Goto 200 can anyone help Dave |
||||
| trippyben Regular Member Joined: 26/06/2011 Location: AustraliaPosts: 91 |
One thing to check: Make sure that the print command terminates the string with a CR and LF character so that the GPS module will receive it correcty. |
||||
| Talbit Senior Member Joined: 07/06/2011 Location: AustraliaPosts: 210 |
Dave, Trippyben has made some interresting points that I'll need to look at. I'm trying to download my program a friend has emailed me. Not an easy task in this location (Cocos Keeling Islands). But I was going to say to you to save the NMEA string as a String$ but it looks like you have tried that. If you can't print out the string then something is wrong somewhere. Almost there - My colleague is trying to get it from her laptop to mine so that I can do a cut and paste. There now !!! 10 ''''''''''' 29 July 2011''''''''''''' 1000 GOSUB 11000 'Initialise the LCD 1010 LCD_line1$ = " Waiting for " 1020 LCD_line2$ = " Satellite Fix " 1030 GOSUB 12000 ' Send to the LCD 1040 PAUSE 5000 ' Wait for 5 seconds 1050 t$ = "$GPRMC,235830,A,3520.6098,S,14909.4911,E,000.0,000.0,150711 ,012.4,E*6A" 1060 GOSUB 2000 'Set the PPS & Time Break pins 1070 GOSUB 2500 'Parse the time and date 1080 GOSUB 3000 'Update the time by 1 second 1100 IF PIN(17)=0 THEN 1120 'Wait for PPS to go low then send time to LCD 1110 GOTO 1100 'Loop back if it's not low 1120 ''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 1130 IF Day =1 THEN 1510 1140 IF Hour =1 THEN 1550 1150 IF Minute=1 THEN 1590 1200 GOSUB 12000 'Send to the LCD 1210 GOTO 1080 1220 END 1500 '''''''''''''''''Time Break Interupts''''''''''''' 1510 PIN(18)=1 'Day Time Break (6 seconds) 1520 SETTICK 6000,2250 1530 GOTO 1200 1540 ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 1550 PIN(18)=1 'Hour Time Break (4 seconds) 1560 SETTICK 4000,2250 1570 GOTO 1200 1580 '''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 1590 PIN(18)=1 'Minute Time Break (2 seconds) 1600 SETTICK 2000,2250 1610 GOTO 1200 2000 ''''''''''''Routine to set the PPS & Time Break pins'''''''''''' 2010 SETPIN 17,2 'Make Pin 17 a digital Input (PPS) 2020 SETPIN 18,8 'Make Pin 18 a digital output (Time Break) 2030 PIN(18)=0 'Make sure Pin 18 is low 2040 RETURN 2250 ''''''''''''''''''''''''''Reset Time Break''''''''''''''' 2260 PIN(18)=0 2270 SETTICK 0,0 2280 IRETURN 2500 '''''''''''''Parse Time & Date''''''''''''''''''''''''''' 2510 parse$ = MID$(t$, 1, 1) 'Get the first character 2520 parse6$ = MID$(t$, 6, 1) 'Get the sixth character 2530 IF parse$ <>"$" THEN 1640 'Test for $, stop if it's not 2540 IF parse6$<>"C" THEN 1640 'Test for $PGRMC, stop if it's not 2550 hh$ = MID$(t$, 8, 2) 'Get the hours 2560 mm$ = MID$(t$, 10, 2) 'Get the minutes 2570 ss$ = MID$(t$, 12, 2) 'Get the seconds 2580 dd$ = MID$(t$, 54, 2) 'Get the days 2590 ll$ = MID$(t$, 56, 2) 'Get the months (ll=months) 2600 yy$ = MID$(t$, 58, 2) 'Get the years 2610 ss = VAL(ss$) 'Change time to an integer 2620 mm = VAL(mm$) 2630 hh = VAL(hh$) 2640 RETURN That's the best I can give you at the moment. The rest is probably not of any interrest to you. Ignore most of the program because it's only at testing stage. But I start with a dummy NMEA string at 1050. I check to see it's the correct string at 2500 then I Parse the time and date then display it on the LCD on the GPS PPS. If you can work out how to get the NMEA string so that you can manipulate it then you should be half way there. I'm keen to know what you come up with. Hope this is of some help. I'm 3.5 hours behind Sydney time. Trevor Talbit |
||||
| Talbit Senior Member Joined: 07/06/2011 Location: AustraliaPosts: 210 |
I presume your line 200 is setting the GPS up to output a particular NMEA sentence. You should only need to do this once after startup. So maybe you should loop back to line 300 instead of 200. Also , in Geoff's example he has a comma after the Print #5 so line 200 should be 200 Print #5, "$PSRF103,4,0,1,1*21" ; What's the ; at the end of line 200 for? And is line 500 to reset Data$ to blank? I'm not sure if you need to do this. Try and simplify it by doing just one read... 100 OPEN "COM1:4800" AS #5 200 Print #5, "$PSRF103,4,0,1,1*21" 250 Pause 2000 'wait 2 seconds 300 Data$ = Input$(50, #5) 350 Close #5 'Close the port 400 Print Data$ 'See if it's there. 500 End If you succeed in seeing the NMEA string at line 400, then you are almost there. I'm itching to get home and get mine going. Trevor Talbit |
||||
| devigan Newbie Joined: 11/08/2011 Location: AustraliaPosts: 26 |
Tried your code I am getting a blank line. how about you |
||||
| devigan Newbie Joined: 11/08/2011 Location: AustraliaPosts: 26 |
I tried even with line 200 remove still the same |
||||
| Talbit Senior Member Joined: 07/06/2011 Location: AustraliaPosts: 210 |
I can't try anything because my MM is 6000klm away. I'm going on my general knowledge with nothing to try it on. Sorry. I'm amazed that you haven't been swamped with offers of help. Come on guys. Help this bloke out !!! Talbit Talbit |
||||
| Talbit Senior Member Joined: 07/06/2011 Location: AustraliaPosts: 210 |
Dave, I've had a closer read of Geoffs notes on the serial. The way I understand it, when you open the serial port it accepts anything that comes along and puts it in the buffer. Then you read the buffer with data$ = input$(50, #5). Then to look at it you Print Data$ So when you do data$ = input$(50, #5) you're not actually looking at the port, but you are extracting data from the buffer. But the program you have tried below should wait for some data to be in the buffer but as you have said you still can't see anything. Can you try the EOF() command to see if there is actually anything there? See Geoffs notes. 100 OPEN "COM1:4800" AS #5 250 Pause 2000 'wait 2 seconds 300 Data$ = Input$(50, #5) 350 Close #5 'Close the port 400 Print Data$ 'See if it's there. 500 End I'm assuming you have your GPS connected to pin 15. It can't be any higher than 5 volts. But check that you are allowed to go as high as 5 volts or does it need to be 3.5volts. I hope you haven't zapped pin 15. Next thing to try is to invert the NMEA stream before you feed it into pin 15. Next you can try this routine... 100 OPEN "COM1:4800, 100, 10000, 50" AS #5 300 print data$ 400 end 10000 close #5 10100 data$ = input$(50, #5) 10200 Ireturn This uses an interrupt but it should only branch to the interrupt if it receives 50 characters into the port. Trevor Talbit |
||||
| Page 1 of 2 |
|||||
 Print this page |
