Hello,I am using an adafruit ultimate GPS logger shield with an Arduino Uno. I am running the example shield_sdlog sketch from the downloaded adafruit GPS library. I'm trying to modify the example program to log some other data side-by-side with the GPS NMEA sentences (literally side by side--I want the log file to contain a NMEA sentence, then several other values on the same line separated by semicolons, then another sentence on a new line). I have identified the part of the code that actually does the logging, and now I am trying to modify it, but I find that I don't even understand it well enough to do that.
Here is the full code of the example sketch:
#include <SPI.h>
#include <Adafruit_GPS.h>
#include <SoftwareSerial.h>
#include <SD.h>
#include <avr/sleep.h>
// Ladyada's logger modified by Bill Greiman to use the SdFat library
//
// This code shows how to listen to the GPS module in an interrupt
// which allows the program to have more 'freedom' - just parse
// when a new NMEA sentence is available! Then access data when
// desired.
//
// Tested and works great with the Adafruit Ultimate GPS Shield
// using MTK33x9 chipset
// ------> http://www.adafruit.com/products/
// Pick one up today at the Adafruit electronics shop
// and help support open source hardware & software! -ada
// Fllybob added 10 sec logging option
SoftwareSerial mySerial(8, 7);
Adafruit_GPS GPS(&mySerial);
// Set GPSECHO to 'false' to turn off echoing the GPS data to the Serial console
// Set to 'true' if you want to debug and listen to the raw GPS sentences
#define GPSECHO true
/* set to true to only log to SD when GPS has a fix, for debugging, keep it false */
#define LOG_FIXONLY false
// this keeps track of whether we're using the interrupt
// off by default!
boolean usingInterrupt = false;
void useInterrupt(boolean); // Func prototype keeps Arduino 0023 happy
// Set the pins used
#define chipSelect 10
#define ledPin 13
File logfile;
// read a Hex value and return the decimal equivalent
uint8_t parseHex(char c) {
if (c < '0')
return 0;
if (c <= '9')
return c - '0';
if (c < 'A')
return 0;
if (c <= 'F')
return (c - 'A')+10;
}
// blink out an error code
void error(uint8_t errno) {
/*
if (SD.errorCode()) {
putstring("SD error: ");
Serial.print(card.errorCode(), HEX);
Serial.print(',');
Serial.println(card.errorData(), HEX);
}
*/
while(1) {
uint8_t i;
for (i=0; i<errno; i++) {
digitalWrite(ledPin, HIGH);
delay(100);
digitalWrite(ledPin, LOW);
delay(100);
}
for (i=errno; i<10; i++) {
delay(200);
}
}
}
void setup() {
// for Leonardos, if you want to debug SD issues, uncomment this line
// to see serial output
//while (!Serial);
// connect at 115200 so we can read the GPS fast enough and echo without dropping chars
// also spit it out
Serial.begin(115200);
Serial.println("\r\nUltimate GPSlogger Shield");
pinMode(ledPin, OUTPUT);
// make sure that the default chip select pin is set to
// output, even if you don't use it:
pinMode(10, OUTPUT);
// see if the card is present and can be initialized:
//if (!SD.begin(chipSelect, 11, 12, 13)) {
if (!SD.begin(chipSelect)) { // if you're using an UNO, you can use this line instead
Serial.println("Card init. failed!");
error(2);
}
char filename[15];
strcpy(filename, "GPSLOG00.TXT");
for (uint8_t i = 0; i < 100; i++) {
filename[6] = '0' + i/10;
filename[7] = '0' + i%10;
// create if does not exist, do not open existing, write, sync after write
if (! SD.exists(filename)) {
break;
}
}
logfile = SD.open(filename, FILE_WRITE);
if( ! logfile ) {
Serial.print("Couldnt create ");
Serial.println(filename);
error(3);
}
Serial.print("Writing to ");
Serial.println(filename);
// connect to the GPS at the desired rate
GPS.begin(9600);
// uncomment this line to turn on RMC (recommended minimum) and GGA (fix data) including altitude
GPS.sendCommand(PMTK_SET_NMEA_OUTPUT_RMCGGA);
// uncomment this line to turn on only the "minimum recommended" data
//GPS.sendCommand(PMTK_SET_NMEA_OUTPUT_RMCONLY);
// For logging data, we don't suggest using anything but either RMC only or RMC+GGA
// to keep the log files at a reasonable size
// Set the update rate
GPS.sendCommand(PMTK_SET_NMEA_UPDATE_1HZ); // 100 millihertz (once every 10 seconds), 1Hz or 5Hz update rate
// Turn off updates on antenna status, if the firmware permits it
GPS.sendCommand(PGCMD_NOANTENNA);
// the nice thing about this code is you can have a timer0 interrupt go off
// every 1 millisecond, and read data from the GPS for you. that makes the
// loop code a heck of a lot easier!
useInterrupt(true);
Serial.println("Ready!");
}
// Interrupt is called once a millisecond, looks for any new GPS data, and stores it
SIGNAL(TIMER0_COMPA_vect) {
char c = GPS.read();
// if you want to debug, this is a good time to do it!
#ifdef UDR0
if (GPSECHO)
if (c) UDR0 = c;
// writing direct to UDR0 is much much faster than Serial.print
// but only one character can be written at a time.
#endif
}
void useInterrupt(boolean v) {
if (v) {
// Timer0 is already used for millis() - we'll just interrupt somewhere
// in the middle and call the "Compare A" function above
OCR0A = 0xAF;
TIMSK0 |= _BV(OCIE0A);
usingInterrupt = true;
}
else {
// do not call the interrupt function COMPA anymore
TIMSK0 &= ~_BV(OCIE0A);
usingInterrupt = false;
}
}
void loop() {
if (! usingInterrupt) {
// read data from the GPS in the 'main loop'
char c = GPS.read();
// if you want to debug, this is a good time to do it!
if (GPSECHO)
if (c) Serial.print(c);
}
// if a sentence is received, we can check the checksum, parse it...
if (GPS.newNMEAreceived()) {
// a tricky thing here is if we print the NMEA sentence, or data
// we end up not listening and catching other sentences!
// so be very wary if using OUTPUT_ALLDATA and trying to print out data
// Don't call lastNMEA more than once between parse calls! Calling lastNMEA
// will clear the received flag and can cause very subtle race conditions if
// new data comes in before parse is called again.
char *stringptr = GPS.lastNMEA();
if (!GPS.parse(stringptr)) // this also sets the newNMEAreceived() flag to false
return; // we can fail to parse a sentence in which case we should just wait for another
// Sentence parsed!
Serial.println("OK");
if (LOG_FIXONLY && !GPS.fix) {
Serial.print("No Fix");
return;
}
// Rad. lets log it!
Serial.println("Log");
uint8_t stringsize = strlen(stringptr);
if (stringsize != logfile.write((uint8_t *)stringptr, stringsize)) //write the string to the SD file
error(4);
if (strstr(stringptr, "RMC") || strstr(stringptr, "GGA")) logfile.flush();
Serial.println();
}
}
/* End code */
Here is just the part that I am trying to understand/modify:
uint8_t stringsize = strlen(stringptr);
if (stringsize != logfile.write((uint8_t *)stringptr, stringsize)) //write the string to the SD file
error(4);
if (strstr(stringptr, "RMC") || strstr(stringptr, "GGA")) logfile.flush();
Serial.println();
Basically I'm trying to remove whatever part of that code puts each sentence on a new line, so that I can add in my data and my own new line statement. However, as I mentioned, I am very confused here. First, understand why these statements seem to contain the actual logging part within an if statement (it was my previous understanding that if statements only decided what sections of other code to run, that they could do things by themselves). Second, I don't understand where the new lines are coming from, because I tried commenting out the Serial.println() statement, and the sentences still appear on different lines (and I'm sure I have the right section because when I comment it out entirely, no logging happens).
So does anyone know what's going in this section? Thanks in advance