In the RTClib.h there is an example program for DS1307 square wave output generator. I have this converted for DS3231.
However, the serial monitor shows the wrong messages: instead of the sequence "OFF", "1Hz", '1.024kHz", "4.096kHz", "8.192kHz" the monitor puts out the following:
"1Hz", 1Hz", "1Hz", "4.096kHz", "4.096kHz"
The actual frequencies put out however are correct.
Following is the example program, underneath is the actual (converted) program:
// SQW/OUT pin mode using a DS1307 RTC connected via I2C.
//
// According to the data sheet (http://datasheets.maxim-ic.com/en/ds/DS1307.pdf), the
// DS1307's SQW/OUT pin can be set to low, high, 1Hz, 4.096kHz, 8.192kHz, or 32.768kHz.
//
// This sketch reads the state of the pin, then iterates through the possible values at
// 5 second intervals.
//
// NOTE:
// You must connect a pull up resistor (~10kohm) from the SQW pin up to VCC. Without
// this pull up the wave output will not work!
#include <Wire.h>
#include "RTClib.h"
#if defined(ARDUINO_ARCH_SAMD)
// for Zero, output on USB Serial console, remove line below if using programming port to program the Zero!
#define Serial SerialUSB
#endif
RTC_DS1307 rtc;
int mode_index = 0;
Ds1307SqwPinMode modes[] = {OFF, ON, SquareWave1HZ, SquareWave4kHz, SquareWave8kHz, SquareWave32kHz};
void print_mode() {
Ds1307SqwPinMode mode = rtc.readSqwPinMode();
Serial.print("Sqw Pin Mode: ");
switch(mode) {
case OFF: Serial.println("OFF"); break;
case ON: Serial.println("ON"); break;
case SquareWave1HZ: Serial.println("1Hz"); break;
case SquareWave4kHz: Serial.println("4.096kHz"); break;
case SquareWave8kHz: Serial.println("8.192kHz"); break;
case SquareWave32kHz: Serial.println("32.768kHz"); break;
default: Serial.println("UNKNOWN"); break;
}
}
void setup () {
#ifndef ESP8266
while (!Serial); // for Leonardo/Micro/Zero
#endif
Serial.begin(57600);
if (! rtc.begin()) {
Serial.println("Couldn't find RTC");
while (1);
}
print_mode();
}
void loop () {
rtc.writeSqwPinMode(modes[mode_index++]);
print_mode();
if (mode_index > 5) {
mode_index = 0;
}
delay(5000);
}
Here is the converted program working with a DS3231 (included and enumerated in the RTClib.h library):
// https://github.com/adafruit/RTClib/blob/master/examples/ds1307SqwPin/ds1307SqwPin.ino
// Aangepast voor DS3231
// SQW/OUT pin mode using a DS3231 RTC connected via I2C.
//
// According to the data sheet (http://datasheets.maxim-ic.com/en/ds/DS1307.pdf), the
// DS1307's SQW/OUT pin can be set to low, 1Hz, 1.024kHz, 4.096kHz, 8.192kHz.
//
// This sketch reads the state of the pin, then iterates through the possible values at
// 5 second intervals.
//
#include <Wire.h>
#include "RTClib.h"
#if defined(ARDUINO_ARCH_SAMD)
// for Zero, output on USB Serial console, remove line below if using programming port to program the Zero!
#define Serial SerialUSB
#endif
RTC_DS3231 rtc;
int mode_index = 0;
Ds3231SqwPinMode modes[] = {DS3231_OFF, DS3231_SquareWave1Hz, DS3231_SquareWave1kHz, DS3231_SquareWave4kHz, DS3231_SquareWave8kHz};
const byte rtcTimerIntPin = 2;
volatile byte flag = false;
void setup () {
pinMode (LED_BUILTIN, OUTPUT);
pinMode (rtcTimerIntPin, INPUT_PULLUP);
attachInterrupt (digitalPinToInterrupt (rtcTimerIntPin), rtc_interrupt, CHANGE);
#ifndef ESP8266
while (!Serial); // for Leonardo/Micro/Zero
#endif
Serial.begin(57600);
if (! rtc.begin()) {
Serial.println("Couldn't find RTC");
while (1);
}
}
void rtc_interrupt ()
{
flag = true;
} // end of rtc_interrupt
void print_mode() {
Ds3231SqwPinMode mode = rtc.readSqwPinMode();
Serial.print("Sqw Pin Mode: ");
switch (mode) {
case DS3231_OFF: Serial.println("OFF"); break;
case DS3231_SquareWave1Hz: Serial.println("1Hz"); break;
case DS3231_SquareWave1kHz: Serial.println("1.024kHz"); break;
case DS3231_SquareWave4kHz: Serial.println("4.096kHz"); break;
case DS3231_SquareWave8kHz: Serial.println("8.192kHz"); break;
default: Serial.println("UNKNOWN"); break;
}
}
void loop () {
rtc.writeSqwPinMode(modes[mode_index++]);
print_mode();
if (mode_index > 4) {
mode_index = 0;
}
delay(5000);
}