TM_GPS

GPS NMEA standard data parser for STM32Fxxx devices - http://stm32f4-discovery.net/2016/07/hal-library-35-gps-parser-stm32fxxx/. More...

Modules
	TM_GPS_Macros
	Library private defines without any sense for USER.
	TM_GPS_Typedefs
	Library Typedefs.
	TM_GPS_Functions
	Library Functions.

Detailed Description

GPS NMEA standard data parser for STM32Fxxx devices - http://stm32f4-discovery.net/2016/07/hal-library-35-gps-parser-stm32fxxx/.

This library parses response from GPS module, in NMEA statements format.

For more, how GPS returns data, look at link below:

http://aprs.gids.nl/nmea/

There is a lot of possible sentences, which can be returned from GPS. This library uses only 4. But some GPS don't returns all of this 4 sentences, so I made a possibility to disable them.

By default, these statements are in use and supported:

• GPGGA: Global Positioning System Fix Data
  • Latitude
  • Longitude
  • Altitude
  • Fix
  • Satellites in use
  • Time
• GPRMC: Recommended minimum specific GPS/Transit data
  • Date
  • Speed
  • Validity
  • Direction
• GPGSA: GPS DOP and Active Satellites
  • HDOP
  • VDOP
  • PDOP
  • FixMode
  • Id's of satellites in use
• GPGSV: GPS Satellites in view
  • Satellites in view
  • Description of all satellites in view
• Custom statements defined by user

By default, each of this data has to be detected in order to get "VALID" data. If your GPS does not return any of this statement, you can disable option. If you disable any of statements, then you will loose data, corresponding to statement.

Add lines below in your defines.h file and uncomment your settings

//Disable GPGGA statement
#define GPS_DISABLE_GPGGA
//Disable GPRMC statement
#define GPS_DISABLE_GPRMC 
//Disable GPGSA statement
#define GPS_DISABLE_GPGSA
//Disable GPGSV statement
#define GPS_DISABLE_GPGSV

Pinout

To communicate with GPS, USART is commonly used. By default, my library uses USART1, but if you want your own USARTx, add lines below in your defines.h file:

#define GPS_USART               USART1
#define GPS_USART_PINSPACK      TM_USART_PinsPack_2

With default pinout:

STM32F4xx TX = PB6
STM32F4xx RX = PB7

Note

Connect GPS's TX to STM32F4xx's RX and vice versa

Increase USART internal buffer

GPS library is based on USART library, which uses internal buffers to store data which are received but not read.

GPS receiver will send a lot of data at a time and if you are doing other stuff that time, it might happen that you will not so quickly update GPS data and buffer will overflow. Default buffer size is for my USART lib 32 bytes.

I recommend that you increase that memory. For further instructions how to do that, look at TM_USART module.

Distance and bearing

Distance between 2 points can not be provided from GPS receiver, so we have to calculate it. This is useful, if you have let’s say quadcopter and you want to know, how far you are from quad. First coordinate will be quad’s current position from GPS and second point will be set before you start with your flight.

If you want to make let’s say “Return home” function on quadcopter, bearing comes to be very useful. GPS module tells you your direction (included in library) where you are currently moving. Still, first coordinate is from quad’s GPS receiver, and second is where quad started with flight. When you activate “Return home” function, quad will know how far he is from “home” and in which direction (bearing) he has to move according to the north. Then, you just have to compare your calculated bearing with actual direction provided from GPS. And you will know, if he needs to go more left, right, etc. You can tune PID then according to values.

Custom GPS statements

Library supports by default 4 statements. It assumes that every GPS module should output these 4 statements. It may happen, that your module outputs data that you need, but are not available with my library by default.

Here is why custom GPS statements come handy. It is possible to define custom statements which will be parsed as strings from GPS receiver directly to user.

For example, let’s say that your module outputs $GPRMB sentence (navigation). From that statement, you want to get “Steering value”, which can be “L” or “R” for Left or Right. Steering value is part 3 inside GPRMB sentence. If you want to include this into your output, you can do this:

//Set variable
TM_GPS_Custom_t* GPRMB_3_Pointer;

//$GPRMB statement, term number 3 = Steering value
GPRMB_3_Pointer = TM_GPS_AddCustom(&GPS_Data, "$GPRMB", 3);

This statement is now added into main GPS_Data structure and also, pointer to small GPRMB.3 structure is returned.

Note

You have to make sure, that in this case, GPRMB statement is really returned from module. If module will not return this statement, you will not be able to read anything from library, because it will never happen that everything will be updated before new data are available.

Changelog

 Version 1.0
  - First release

Dependencies

 - STM32Fxxx HAL
 - defines.h
 - TM USART
 - TM GPIO
 - defines.h
 - math.h