The code is Jordi's new NMEA parser for the Locosys GPS. It's checksum verified, rocksolid, continuous, no delays, loop rate is about 32000hz. It uses pointers, so it's efficient.
You have to configure the Locosys for the first time you use it. It's very easy, you just need an FTDI cable. Be sure to connect the GPS to a 3.3 volt source. (We'll do this setup for you in the commercial version)
Instructions (please use the picture above as reference):
1-Run Realterminal and open the port @4800bps, you should see all the NMEA stuff, is not check the connections..
2-Now make sure you have checked the options marked with the green arrow... +CR +LF
3-Copy and paste this code: $PMTK251,38400*27 to the box indicated with the red arrow.
4-Then click the "Send ASCII" button indicated with the blue arrow..
5-Then the NMEA should disappear, and starting showing strange values. Go back to the "Port tab" (yellow arrow),
close the port, and choose the Baud "38400", and open the port again. You should the NMEA data again... =)
6- Then go back to the "Send" tab, and copy&paste this code: $PMTK314,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0*28 then click Send, this should turn Off all sentences except GGA and RMC
7-Copy&paste now this code: $PMTK220,200*2C This should increase the updates to 5hz... (WOW!!!)..
8- Now you are able to connect the GPS module to Arduino, (only connect the RX pin to the TX of the GPS)
9-Then upload the code above, and open the port monitor, you should see Lat, Lon, Course, Speed, Altitude, Fix Position... like this:
46024504 8050998 312 0 519 1 (and yes you now know the exact position of my Swiss Chalet =P)...
If you want other setup codes for this GPS, you can find them in this datasheet.
Code explanation
If you'd like to understand the NMEA parser code a bit better, here are some of the library functions that it calls (all from the standard C++ library):
- First of all pointers, which are very easy. They just give you the memory address where a variable is allocated in the ram: info
- Then the strncmp(), better know as String Comparator. We use it to compare the header of the NMEA string "$GPGGA": info
- Then strtl(), which means String to Long Variable. It converts a string number into a long variable: info
- Then the strtok(). This is the string tokens, which looks for tokens in a string, for example commas ",", the ones used to separate values in the NMEA sentence: info
- The atoi() will convert strings to integers: info
- If you want to know all the available functions, see the library called "strings.h", "stdlib.h": info and info
Comments
I'll roll back till it works lol
Dont have $150 for a new gps, I have too many already ;)
I'll test both of them with the current code and see if I can replicate your error.
Im having problems with my 406 GPS (I think) - seems to test ok but ardu wont get a lock, so ive got a spare locosys sitting here I want to use.
I followed the instructions in this thread, set the Loco to 5HZ, 38400 baud & changed the output stream to suit ardu- all good.
Tested the gps via the serial port with MiniGPS / realterm. It lock onto sat's very reliably. 36seconds from cold start was the best - COOL!
Yeah ok so I set the ardu code to NEMA and also my shield to the old red version but I cant seem to get ardu to get a solid blue light :(
Is there something special I need to do as this thread is very old and I suspect things have changed, im using the 2.5.3 code.
Thanks! :)
I notice the ardupilot can only function by using GPS module like EM406 or 5HZ type..Please advise me if the ardupilot is capable to control it by using other type of GPS i.e. not a programmable GPS but with display unit like iPAQ or Raymarine GPS's...All the best..
I would love the link to the code...
Thanks
If iyou need a copy, just shout....i will post a link to it.
by the way, if you get 5hz, let me know, not had anything over 4hz.....either way, compared to the trusty old EM406.....its pretty cool
regards,
Doc
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