Hello,
As I'm playing around with an example from Ladyada (the gps logger pde that can be found here : GitHub - adafruit/SD-Basic-GPS-logger), I found some #if and some if but I don't get what is the difference when using one or the other
... I looked quickly in the search functionnality (searching #if, if, difference ... ) but I couldn't find an explanation. My appologies if this is basic beginner question
Here is the complete code :
// Ladyada's logger modified by Bill Greiman to use the SdFat library
// this is a generic logger that does checksum testing so the data written should be always good
// Assumes a sirf III chipset logger attached to pin 2 and 3
#include <SD.h>
#include <avr/sleep.h>
#include "GPSconfig.h"
// Make sure to install newsoftserial from Mikal Hart
// http://arduiniana.org/libraries/NewSoftSerial/
#include <NewSoftSerial.h>
// power saving modes
#define SLEEPDELAY 0
#define TURNOFFGPS 0
#define LOG_RMC_FIXONLY 0
// what to log
#define LOG_RMC 1 // RMC-Recommended Minimum Specific GNSS Data, message 103,04
#define LOG_GGA 0 // GGA-Global Positioning System Fixed Data, message 103,00
#define LOG_GLL 0 // GLL-Geographic Position-Latitude/Longitude, message 103,01
#define LOG_GSA 0 // GSA-GNSS DOP and Active Satellites, message 103,02
#define LOG_GSV 0 // GSV-GNSS Satellites in View, message 103,03
#define LOG_VTG 0 // VTG-Course Over Ground and Ground Speed, message 103,05
// Use pins 2 and 3 to talk to the GPS. 2 is the TX pin, 3 is the RX pin
NewSoftSerial gpsSerial = NewSoftSerial(2, 3);
// Set the GPSRATE to the baud rate of the GPS module. Most are 4800
// but some are 38400 or other. Check the datasheet!
#define GPSRATE 4800
// Set the pins used
#define powerPin 4
#define led1Pin 5
#define led2Pin 6
#define chipSelect 10
#define BUFFSIZE 90
char buffer[BUFFSIZE];
uint8_t bufferidx = 0;
uint8_t fix = 0; // current fix data
uint8_t i;
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) {
for (i=0; i<errno; i++) {
digitalWrite(led1Pin, HIGH);
digitalWrite(led2Pin, HIGH);
delay(100);
digitalWrite(led1Pin, LOW);
digitalWrite(led2Pin, LOW);
delay(100);
}
for (; i<10; i++) {
delay(200);
}
}
}
void setup() {
WDTCSR |= (1 << WDCE) | (1 << WDE);
WDTCSR = 0;
Serial.begin(9600);
Serial.println("\r\nGPSlogger");
pinMode(led1Pin, OUTPUT);
pinMode(led2Pin, OUTPUT);
pinMode(powerPin, OUTPUT);
digitalWrite(powerPin, LOW);
// 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)) {
Serial.println("Card init. failed!");
error(1);
}
strcpy(buffer, "GPSLOG00.TXT");
for (i = 0; i < 100; i++) {
buffer[6] = '0' + i/10;
buffer[7] = '0' + i%10;
// create if does not exist, do not open existing, write, sync after write
if (! SD.exists(buffer)) {
break;
}
}
logfile = SD.open(buffer, FILE_WRITE);
if( ! logfile ) {
Serial.print("Couldnt create "); Serial.println(buffer);
error(3);
}
Serial.print("Writing to "); Serial.println(buffer);
// connect to the GPS at the desired rate
gpsSerial.begin(GPSRATE);
Serial.println("Ready!");
gpsSerial.print(SERIAL_SET);
delay(250);
#if (LOG_DDM == 1)
gpsSerial.print(DDM_ON);
#else
gpsSerial.print(DDM_OFF);
#endif
delay(250);
#if (LOG_GGA == 1)
gpsSerial.print(GGA_ON);
#else
gpsSerial.print(GGA_OFF);
#endif
delay(250);
#if (LOG_GLL == 1)
gpsSerial.print(GLL_ON);
#else
gpsSerial.print(GLL_OFF);
#endif
delay(250);
#if (LOG_GSA == 1)
gpsSerial.print(GSA_ON);
#else
gpsSerial.print(GSA_OFF);
#endif
delay(250);
#if (LOG_GSV == 1)
gpsSerial.print(GSV_ON);
#else
gpsSerial.print(GSV_OFF);
#endif
delay(250);
#if (LOG_RMC == 1)
gpsSerial.print(RMC_ON);
#else
gpsSerial.print(RMC_OFF);
#endif
delay(250);
#if (LOG_VTG == 1)
gpsSerial.print(VTG_ON);
#else
gpsSerial.print(VTG_OFF);
#endif
delay(250);
#if (USE_WAAS == 1)
gpsSerial.print(WAAS_ON);
#else
gpsSerial.print(WAAS_OFF);
#endif
}
void loop() {
//Serial.println(Serial.available(), DEC);
char c;
uint8_t sum;
// read one 'line'
if (gpsSerial.available()) {
c = gpsSerial.read();
//Serial.print(c, BYTE);
if (bufferidx == 0) {
while (c != '
I understand this section is to choose which mode you want to see activated in the gps :
// what to log
#define LOG_RMC 1 // RMC-Recommended Minimum Specific GNSS Data, message 103,04
#define LOG_GGA 0 // GGA-Global Positioning System Fixed Data, message 103,00
#define LOG_GLL 0 // GLL-Geographic Position-Latitude/Longitude, message 103,01
#define LOG_GSA 0 // GSA-GNSS DOP and Active Satellites, message 103,02
#define LOG_GSV 0 // GSV-GNSS Satellites in View, message 103,03
#define LOG_VTG 0 // VTG-Course Over Ground and Ground Speed, message 103,05
... and this is where is activates it or not (in the setup())
#if (LOG_DDM == 1)
gpsSerial.print(DDM_ON);
#else
gpsSerial.print(DDM_OFF);
#endif
delay(250);
#if (LOG_GGA == 1)
gpsSerial.print(GGA_ON);
#else
gpsSerial.print(GGA_OFF);
#endif
delay(250);
#if (LOG_GLL == 1)
gpsSerial.print(GLL_ON);
#else
gpsSerial.print(GLL_OFF);
#endif
delay(250);
#if (LOG_GSA == 1)
gpsSerial.print(GSA_ON);
#else
gpsSerial.print(GSA_OFF);
#endif
delay(250);
#if (LOG_GSV == 1)
gpsSerial.print(GSV_ON);
#else
gpsSerial.print(GSV_OFF);
#endif
delay(250);
#if (LOG_RMC == 1)
gpsSerial.print(RMC_ON);
#else
gpsSerial.print(RMC_OFF);
#endif
delay(250);
#if (LOG_VTG == 1)
gpsSerial.print(VTG_ON);
#else
gpsSerial.print(VTG_OFF);
#endif
delay(250);
#if (USE_WAAS == 1)
gpsSerial.print(WAAS_ON);
#else
gpsSerial.print(WAAS_OFF);
#endif
... So why is there #if and not the usual if
)
c = gpsSerial.read(); // wait till we get a $
}
buffer[bufferidx] = c;
//Serial.print(c, BYTE);
if (c == '\n') {
//putstring_nl("EOL");
//Serial.print(buffer);
buffer[bufferidx+1] = 0; // terminate it
if (buffer[bufferidx-4] != '') {
// no checksum?
Serial.print('', BYTE);
bufferidx = 0;
return;
}
// get checksum
sum = parseHex(buffer[bufferidx-3]) * 16;
sum += parseHex(buffer[bufferidx-2]);
// check checksum
for (i=1; i < (bufferidx-4); i++) {
sum ^= buffer[i];
}
if (sum != 0) {
//putstring_nl("Cxsum mismatch");
Serial.print('~', BYTE);
bufferidx = 0;
return;
}
// got good data!
if (strstr(buffer, "GPRMC")) {
// find out if we got a fix
char *p = buffer;
p = strchr(p, ',')+1;
p = strchr(p, ',')+1; // skip to 3rd item
if (p[0] == 'V') {
digitalWrite(led1Pin, LOW);
fix = 0;
} else {
digitalWrite(led1Pin, HIGH);
fix = 1;
}
}
if (LOG_RMC_FIXONLY) {
if (!fix) {
Serial.print('_', BYTE);
bufferidx = 0;
return;
}
}
// rad. lets log it!
Serial.print(buffer);
Serial.print('#', BYTE);
digitalWrite(led2Pin, HIGH); // sets the digital pin as output
// Bill Greiman - need to write bufferidx + 1 bytes to getCR/LF
bufferidx++;
logfile.write((uint8_t ) buffer, bufferidx);
logfile.flush();
/
if( != bufferidx) {
putstring_nl("can't write!");
error(4);
}
*/
digitalWrite(led2Pin, LOW);
bufferidx = 0;
// turn off GPS module?
if (TURNOFFGPS) {
digitalWrite(powerPin, HIGH);
}
sleep_sec(SLEEPDELAY);
digitalWrite(powerPin, LOW);
return;
}
bufferidx++;
if (bufferidx == BUFFSIZE-1) {
Serial.print('!', BYTE);
bufferidx = 0;
}
} else {
}
}
void sleep_sec(uint8_t x) {
while (x--) {
// set the WDT to wake us up!
WDTCSR |= (1 << WDCE) | (1 << WDE); // enable watchdog & enable changing it
WDTCSR = (1<< WDE) | (1 <<WDP2) | (1 << WDP1);
WDTCSR |= (1<< WDIE);
set_sleep_mode(SLEEP_MODE_PWR_DOWN);
sleep_enable();
sleep_mode();
sleep_disable();
}
}
SIGNAL(WDT_vect) {
WDTCSR |= (1 << WDCE) | (1 << WDE);
WDTCSR = 0;
}
/* End code */
I understand this section is to choose which mode you want to see activated in the gps :
§DISCOURSE_HOISTED_CODE_1§
... and this is where is activates it or not (in the **setup()**)
§DISCOURSE_HOISTED_CODE_2§
... So why is there **#if** and not the usual **if**