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I'm not sure whether we are at cross understanding, or I'm displaying my ignorance. I have read the current time from the RTC and created displayTime(), which writes the result to the serial monitor. What I'm seeking is some way to 'extract' the contents of displayTime() into a string.
If you wrote displayTime then you should know how to use the data already.
BTW, the rtc time is less accurate than the system time. It is only used to set the system time at boot, after which it is updated independently. When the system shuts down, the rtc is reset to what the system has.
In addition, most systems are using NTP (or equivalent) to keep the system time even more accurately. Thus the rtc only serves as an initial "guess" after which NTP is used to get the clock to the correct time. Again, the rtc is really an inaccurate clock as it gains/loses time just due to environment changes.
af7567, your suggestion returned: 164:18: error: void value not ignored as it ought to be (164:18 was the "=")
Here is the complete Arduino sketch:
Code:
#include "Wire.h"
#include <SPI.h>
#include <SD.h>
const int chipSelect = 10; //added
#define DS3231_I2C_ADDRESS 0x68
// Convert normal decimal numbers to binary coded decimal
byte decToBcd(byte val)
{
return( (val/10*16) + (val%10) );
}
// Convert binary coded decimal to normal decimal numbers
byte bcdToDec(byte val)
{
return( (val/16*10) + (val%16) );
}
void setup()
{
Wire.begin();
Serial.begin(9600);
while (!Serial) {
; // wait for serial port to connect. Needed for native USB port only
}
// Serial.print("Initializing SD card...");
// see if the card is present and can be initialized:
if (!SD.begin(chipSelect)) {
Serial.println("Card failed, or not present");
// don't do anything more:
return;
}
// Serial.println("card initialized.");
}
void readDS3231time(byte *second,
byte *minute,
byte *hour,
byte *dayOfWeek,
byte *dayOfMonth,
byte *month,
byte *year)
{
Wire.beginTransmission(DS3231_I2C_ADDRESS);
Wire.write(0); // set DS3231 register pointer to 00h
Wire.endTransmission();
Wire.requestFrom(DS3231_I2C_ADDRESS, 7);
// request seven bytes of data from DS3231 starting from register 00h
*second = bcdToDec(Wire.read() & 0x7f);
*minute = bcdToDec(Wire.read());
*hour = bcdToDec(Wire.read() & 0x3f);
*dayOfWeek = bcdToDec(Wire.read());
*dayOfMonth = bcdToDec(Wire.read());
*month = bcdToDec(Wire.read());
*year = bcdToDec(Wire.read());
}
void displayTime()
{
byte second, minute, hour, dayOfWeek, dayOfMonth, month, year;
// retrieve data from DS3231
readDS3231time(&second, &minute, &hour, &dayOfWeek, &dayOfMonth, &month, &year);
// send it to the serial monitor
Serial.print(" ");
Serial.print(dayOfMonth, DEC);
Serial.print("/");
Serial.print(month, DEC);
Serial.print("/");
Serial.print("20");
Serial.print(year, DEC);
Serial.print(" ");
Serial.print(hour, DEC);
// convert the byte variable to a decimal number when displayed
Serial.print(":");
if (minute<10)
{
Serial.print("0");
}
Serial.print(minute, DEC);
Serial.print(":");
if (second<10)
{
Serial.print("0");
}
Serial.print(second, DEC);
Serial.print(" "); // Serial.print(" Day of week: ");
switch(dayOfWeek){
case 1:
Serial.println("Sunday");
break;
case 2:
Serial.println("Monday");
break;
case 3:
Serial.println("Tuesday");
break;
case 4:
Serial.println("Wednesday");
break;
case 5:
Serial.println("Thursday");
break;
case 6:
Serial.println("Friday");
break;
case 7:
Serial.println("Saturday");
break;
}
}
void loop()
{
// make a string for assembling the data to log:
String dataString = "";
// read three sensors and append to the string:
for (int analogPin = 0; analogPin < 3; analogPin++) {
int sensor = analogRead(analogPin);
dataString += String(sensor);
if (analogPin < 2) {
dataString += ",";
}
}
// open the file.
File dataFile = SD.open("datalog.txt", FILE_WRITE);
// if the file is available, write to it:
if (dataFile) {
dataFile.println(dataString);
dataFile.close();
// print to the serial port too:
Serial.print(dataString);
// Serial.println(displayTime);
// displayTime(); // display the real-time clock data on the Serial Monitor,
displayTime();
delay(10000); // every second
}
}
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