mirror of https://github.com/ArduPilot/ardupilot
225 lines
6.5 KiB
C++
225 lines
6.5 KiB
C++
/*
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GPS_MTK.cpp - Ublox GPS library for Arduino
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Code by Jordi Muñoz and Jose Julio. DIYDrones.com
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This code works with boards based on ATMega168/328 and ATMega1280/2560 (Serial port 1)
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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GPS configuration : Costum protocol
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Baud rate : 38400
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Methods:
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Init() : GPS Initialization
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Read() : Call this funcion as often as you want to ensure you read the incomming gps data
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Properties:
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Lattitude : Lattitude * 10,000,000 (long value)
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Longitude : Longitude * 10,000,000 (long value)
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Altitude : Altitude * 100 (meters) (long value)
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Ground_speed : Speed (m/s) * 100 (long value)
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Ground_course : Course (degrees) * 100 (long value)
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NewData : 1 when a new data is received.
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You need to write a 0 to NewData when you read the data
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Fix : 0: GPS NO FIX or 2D FIX, 1: 3D FIX.
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*/
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#include "GPS_MTK.h"
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#include <avr/interrupt.h>
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#include "WProgram.h"
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// Constructors ////////////////////////////////////////////////////////////////
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GPS_MTK_Class::GPS_MTK_Class()
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{
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}
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// Public Methods //////////////////////////////////////////////////////////////
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void GPS_MTK_Class::Init(void)
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{
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delay(200);
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ck_a=0;
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ck_b=0;
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UBX_step=0;
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NewData=0;
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Fix=0;
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PrintErrors=0;
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GPS_timer=millis(); //Restarting timer...
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// Initialize serial port
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#if defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
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Serial1.begin(38400); // Serial port 1 on ATMega1280/2560
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#else
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Serial.begin(38400);
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#endif
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Serial1.print("$PGCMD,16,0,0,0,0,0*6A\r\n");
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//Serial.println("sent config string");
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}
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// optimization : This code don´t wait for data, only proccess the data available
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// We can call this function on the main loop (50Hz loop)
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// If we get a complete packet this function calls parse_ubx_gps() to parse and update the GPS info.
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void GPS_MTK_Class::Read(void)
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{
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static unsigned long GPS_timer=0;
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byte data;
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int numc;
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#if defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__) // If AtMega1280/2560 then Serial port 1...
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numc = Serial1.available();
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#else
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numc = Serial.available();
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#endif
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if (numc > 0)
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for (int i=0;i<numc;i++) // Process bytes received
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{
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#if defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
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data = Serial1.read();
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#else
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data = Serial.read();
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#endif
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switch(UBX_step) //Normally we start from zero. This is a state machine
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{
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case 0:
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if(data==0xB5) // UBX sync char 1
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UBX_step++; //OH first data packet is correct, so jump to the next step
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break;
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case 1:
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if(data==0x62) // UBX sync char 2
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UBX_step++; //ooh! The second data packet is correct, jump to the step 2
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else
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UBX_step=0; //Nop, is not correct so restart to step zero and try again.
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break;
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case 2:
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UBX_class=data;
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ubx_checksum(UBX_class);
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UBX_step++;
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break;
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case 3:
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UBX_id=data;
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UBX_step=4;
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UBX_payload_length_hi=26;
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UBX_payload_length_lo=0;
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UBX_payload_counter=0;
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ubx_checksum(UBX_id);
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break;
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case 4:
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if (UBX_payload_counter < UBX_payload_length_hi) // We stay in this state until we reach the payload_length
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{
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UBX_buffer[UBX_payload_counter] = data;
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ubx_checksum(data);
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UBX_payload_counter++;
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if (UBX_payload_counter==UBX_payload_length_hi)
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UBX_step++;
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}
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break;
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case 5:
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UBX_ck_a=data; // First checksum byte
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UBX_step++;
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break;
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case 6:
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UBX_ck_b=data; // Second checksum byte
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// We end the GPS read...
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if((ck_a==UBX_ck_a)&&(ck_b==UBX_ck_b)) // Verify the received checksum with the generated checksum..
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parse_ubx_gps(); // Parse the new GPS packet
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else
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{
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if (PrintErrors)
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Serial.println("ERR:GPS_CHK!!");
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}
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// Variable initialization
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UBX_step=0;
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ck_a=0;
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ck_b=0;
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GPS_timer=millis(); //Restarting timer...
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break;
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}
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} // End for...
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// If we don´t receive GPS packets in 2 seconds => Bad FIX state
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if ((millis() - GPS_timer)>2000)
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{
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Fix = 0;
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if (PrintErrors)
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Serial.println("ERR:GPS_TIMEOUT!!");
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}
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}
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/****************************************************************
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*
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****************************************************************/
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// Private Methods //////////////////////////////////////////////////////////////
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void GPS_MTK_Class::parse_ubx_gps(void)
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{
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int j;
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//Verifing if we are in class 1, you can change this "IF" for a "Switch" in case you want to use other UBX classes..
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//In this case all the message im using are in class 1, to know more about classes check PAGE 60 of DataSheet.
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if(UBX_class==0x01)
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{
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switch(UBX_id)//Checking the UBX ID
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{
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case 0x05: //ID Custom
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j=0;
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Lattitude= join_4_bytes(&UBX_buffer[j]) * 10; // lon*10,000,000
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j+=4;
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Longitude = join_4_bytes(&UBX_buffer[j]) * 10; // lat*10000000
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j+=4;
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Altitude = join_4_bytes(&UBX_buffer[j]); // MSL
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j+=4;
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Ground_Speed = join_4_bytes(&UBX_buffer[j]);
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j+=4;
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Ground_Course = join_4_bytes(&UBX_buffer[j]) / 10000; // Heading 2D
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j+=4;
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NumSats=UBX_buffer[j];
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j++;
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Fix=UBX_buffer[j];
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if (Fix==3)
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Fix = 1;
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else
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Fix = 0;
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j++;
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Time = join_4_bytes(&UBX_buffer[j]);
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NewData=1;
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break;
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}
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}
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}
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/****************************************************************
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*
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****************************************************************/
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// Join 4 bytes into a long
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long GPS_MTK_Class::join_4_bytes(unsigned char Buffer[])
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{
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union long_union {
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int32_t dword;
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uint8_t byte[4];
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} longUnion;
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longUnion.byte[3] = *Buffer;
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longUnion.byte[2] = *(Buffer+1);
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longUnion.byte[1] = *(Buffer+2);
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longUnion.byte[0] = *(Buffer+3);
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return(longUnion.dword);
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}
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/****************************************************************
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*
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****************************************************************/
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// checksum algorithm
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void GPS_MTK_Class::ubx_checksum(byte ubx_data)
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{
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ck_a+=ubx_data;
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ck_b+=ck_a;
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}
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GPS_MTK_Class GPS; |