I am using an Arduino Uno and Adafruit datalogging shield. I need to be able to log all the data to an SD card every millisecond. How do i incorporate buffers into my code so I can write data to the card from one buffer while the data is constantly being collected to the other buffer?
Here is my code
#include <SD.h>
#include <Wire.h>
#include "RTClib.h"
#include "DHT.h"
// A simple data logger for the Arduino analog pins
// how many milliseconds between grabbing data and logging it. 1000 ms is once a second
#define LOG_INTERVAL 10 // mills between entries (ECG)
#define SYNC_INTERVAL (1) // mills between calls to flush() - to write data to the card
uint32_t syncTime = 0; // time of last sync()
#define ECHO_TO_SERIAL 0 // echo data to serial port
#define WAIT_TO_START 0 // Wait for serial input in setup()
// the digital pins that connect to the LEDs
#define DHTPin 3 // what pin we're connected to
#define DHTTYPE DHT22
// The analog pins that connect to the sensors
#define ecgPin 0
#define C02Pin 1
DHT dht(DHTPin, DHTTYPE);
RTC_DS1307 RTC; // define the Real Time Clock object
// for the data logging shield, we use digital pin 10 for the SD cs line
const int chipSelect = 10;
// the logging file
File logfile;
void error(char *str)
{
Serial.print("error: ");
Serial.println(str);
while(1);
}
void setup(void)
{
Serial.begin(9600);
Serial.println();
dht.begin();
#if WAIT_TO_START
Serial.println("Type any character to start");
while (!Serial.available());
#endif //WAIT_TO_START
// initialize the SD card
Serial.print("Initializing SD card...");
// 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)) {
error("Card failed, or not present");
}
Serial.println("card initialized.");
// create a new file
char filename[] = "LOGGER00.CSV";
for (uint8_t i = 0; i < 100; i++) {
filename[6] = i/10 + '0';
filename[7] = i%10 + '0';
if (! SD.exists(filename)) {
// only open a new file if it doesn't exist
logfile = SD.open(filename, FILE_WRITE);
break; // leave the loop!
}
}
if (! logfile) {
error("couldnt create file");
}
Serial.print("Logging to: ");
Serial.println(filename);
// connect to RTC
Wire.begin();
if (!RTC.begin()) {
logfile.println("RTC failed");
#if ECHO_TO_SERIAL
Serial.println("RTC failed");
#endif //ECHO_TO_SERIAL
}
logfile.println("millis,stamp,datetime,ecg,C02,rh,temp_c,temp_f,sat_vapor_density,vapor_density");
#if ECHO_TO_SERIAL
Serial.println("millis,stamp,datetime,ecg,C02,rh,temp_c,temp_f,sat_vapor_density,vapor_density");
#endif //ECHO_TO_SERIAL
}
// If you want to set the aref to something other than 5v
//analogReference(EXTERNAL);
void loop(void)
{
DateTime now;
// delay for the amount of time we want between readings
delay((LOG_INTERVAL -1) - (millis() % LOG_INTERVAL));
String dataString = "";
// log milliseconds since starting
uint32_t m = millis();
logfile.print(m); // milliseconds since start
logfile.print(", ");
#if ECHO_TO_SERIAL
Serial.print(m); // milliseconds since start
Serial.print(", ");
#endif
// fetch the time
now = RTC.now();
// log time
logfile.print(now.unixtime()); // seconds since 1/1/1970
logfile.print(", ");
logfile.print('"');
logfile.print(now.year(), DEC);
logfile.print("/");
logfile.print(now.month(), DEC);
logfile.print("/");
logfile.print(now.day(), DEC);
logfile.print(" ");
logfile.print(now.hour(), DEC);
logfile.print(":");
logfile.print(now.minute(), DEC);
logfile.print(":");
logfile.print(now.second(), DEC);
logfile.print('"');
#if ECHO_TO_SERIAL
Serial.print(now.unixtime()); // seconds since 1/1/1970
Serial.print(", ");
Serial.print('"');
Serial.print(now.year(), DEC);
Serial.print("/");
Serial.print(now.month(), DEC);
Serial.print("/");
Serial.print(now.day(), DEC);
Serial.print(" ");
Serial.print(now.hour(), DEC);
Serial.print(":");
Serial.print(now.minute(), DEC);
Serial.print(":");
Serial.print(now.second(), DEC);
Serial.print('"');
#endif //ECHO_TO_SERIAL
analogRead(ecgPin);
delay(0);
int ecgReading = analogRead(ecgPin);
analogRead(C02Pin);
delay(0);
int C02Reading = analogRead(C02Pin);
logfile.print(", ");
logfile.print(ecgReading);
logfile.print(", ");
logfile.print(C02Reading);
logfile.print(", ");
#if ECHO_TO_SERIAL
logfile.print(", ");
logfile.print(ecgReading);
logfile.print(", ");
logfile.print(C02Reading);
logfile.print(", ");
#endif //ECHO_TO_SERIAL
// Reading temperature or humidity takes about 250 milliseconds!
// Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
float h = dht.readHumidity(); // relative humidity, %
float t_c = dht.readTemperature(); // air temp, degC
float t_f = t_c*9.0/5.0 + 32.0; // air temp, degF
float svd; // saturation vapor density, g/m3
float vd; // vapor density, g/m3
// check if returns are valid, if they are NaN (not a number) then something went wrong!
if (isnan(t_c) || isnan(h)) {
Serial.println("Failed to read from DHT");
} else {
svd = 5.018 + 0.32321t_c + 8.1847e-3pow(t_c,2) + 3.1243e-4pow(t_c,3);
vd = h/100svd;
logfile.print(",");
logfile.print(h, 2);
logfile.print(",");
logfile.print(t_c, 2);
logfile.print(",");
logfile.print(t_f, 2);
logfile.print(",");
logfile.print(svd, 4);
logfile.print(",");
logfile.print(vd, 4);
#if ECHO_TO_SERIAL
Serial.print(",");
Serial.print(h, 2);
Serial.print(",");
Serial.print(t_c, 2);
Serial.print(",");
Serial.print(t_f, 2);
Serial.print(",");
Serial.print(svd, 4);
Serial.print(",");
Serial.print(vd, 4);
#endif //ECHO_TO_SERIAL
}
logfile.println();
#if ECHO_TO_SERIAL
Serial.println();
#endif // ECHO_TO_SERIAL
// Now we write data to disk! Don't sync too often - requires 2048 bytes of I/O to SD card
// which uses a bunch of power and takes time
if ((millis() - syncTime) < SYNC_INTERVAL) return;
syncTime = millis();
logfile.flush();
}
