I have a DS1307 & AT24C32 chip combination on a small RTC board bought via eBay. This is billed as "version 2" and has a slightly smaller crystal than most of the others on sale from China.
I had to add edge connectors - no problem, but because of the battery overlapping the solder pads, the battery had to be removed to solder the connectors. Connections were then made to the Mega 2560, powered by the USB: +5V and Gnd to the same pins on the 2560; SDA and SCL again to the equivalent pins in the "Communication" connectors.
I have tried a number of programs, including ones with specific libraries, but have been unable to get this board to function properly. For the purposes of describing this problem here I have reverted to the simplest possible code, first to set the time and secondly to read the time. This code is from here: http://bildr.org/2011/03/ds1307-arduino/
The code to set the time is here:
//Arduino 1.0+ Only
//Arduino 1.0+ Only
#include "Wire.h"
#define DS1307_ADDRESS 0x68
byte zero = 0x00; //workaround for issue #527
void setup(){
Wire.begin();
Serial.begin(9600);
setDateTime(); //MUST CONFIGURE IN FUNCTION
}
void loop(){
printDate();
delay(1000);
}
void setDateTime(){
byte second = 00; //0-59
byte minute = 57; //0-59
byte hour = 18; //0-23
byte weekDay = 1; //1-7
byte monthDay = 15; //1-31
byte month = 7; //1-12
byte year = 12; //0-99
Wire.beginTransmission(DS1307_ADDRESS);
Wire.write(zero); //stop Oscillator
Wire.write(decToBcd(second));
Wire.write(decToBcd(minute));
Wire.write(decToBcd(hour));
Wire.write(decToBcd(weekDay));
Wire.write(decToBcd(monthDay));
Wire.write(decToBcd(month));
Wire.write(decToBcd(year));
Wire.write(zero); //start
Wire.endTransmission();
}
byte decToBcd(byte val){
// Convert normal decimal numbers to binary coded decimal
return ( (val/10*16) + (val%10) );
}
byte bcdToDec(byte val) {
// Convert binary coded decimal to normal decimal numbers
return ( (val/16*10) + (val%16) );
}
void printDate(){
// Reset the register pointer
Wire.beginTransmission(DS1307_ADDRESS);
Wire.write(zero);
Wire.endTransmission();
Wire.requestFrom(DS1307_ADDRESS, 7);
int second = bcdToDec(Wire.read());
int minute = bcdToDec(Wire.read());
int hour = bcdToDec(Wire.read() & 0b111111); //24 hour time
int weekDay = bcdToDec(Wire.read()); //0-6 -> sunday - Saturday
int monthDay = bcdToDec(Wire.read());
int month = bcdToDec(Wire.read());
int year = bcdToDec(Wire.read());
//print the date EG 3/1/11 23:59:59
Serial.print(month);
Serial.print("/");
Serial.print(monthDay);
Serial.print("/");
Serial.print(year);
Serial.print(" ");
Serial.print(hour);
Serial.print(":");
Serial.print(minute);
Serial.print(":");
Serial.println(second);
}
This code is compiled and downloaded ONCE just 10 seconds before the due time (approximately the time taken to transfer). This is a crude - but for testing purposes, acceptable approximation to real world time.
Without disconnecting or resetting or anything else, the following READ code is compiled and sent to the 2560:
//Arduino 1.0+ Only
//Arduino 1.0+ Only
#include "Wire.h"
#define DS1307_ADDRESS 0x68
void setup(){
Wire.begin();
Serial.begin(9600);
}
void loop(){
printDate();
delay(1000);
}
byte bcdToDec(byte val) {
// Convert binary coded decimal to normal decimal numbers
return ( (val/16*10) + (val%16) );
}
void printDate(){
// Reset the register pointer
Wire.beginTransmission(DS1307_ADDRESS);
byte zero = 0x00;
Wire.write(zero);
Wire.endTransmission();
Wire.requestFrom(DS1307_ADDRESS, 7);
int second = bcdToDec(Wire.read());
int minute = bcdToDec(Wire.read());
int hour = bcdToDec(Wire.read() & 0b111111); //24 hour time
int weekDay = bcdToDec(Wire.read()); //0-6 -> sunday - Saturday
int monthDay = bcdToDec(Wire.read());
int month = bcdToDec(Wire.read());
int year = bcdToDec(Wire.read());
//print the date EG 3/1/11 23:59:59
Serial.print(month);
Serial.print("/");
Serial.print(monthDay);
Serial.print("/");
Serial.print(year);
Serial.print(" ");
Serial.print(hour);
Serial.print(":");
Serial.print(minute);
Serial.print(":");
Serial.println(second);
}
This should ensure the setting of the RTC time occurs only once and that, from then on, reading the RTC should give a reasonable approximation to real-world time.
The problem that I have is that the clock starts from 7/15/12 18:57:00 and increments every second to 7/15/12 18:57:19 it then resets back to 7/15/12 18:57:00. When the RTC is unplugged from the Arduino or the Arduino is powered down the time always starts from 7/15/12 18:57:00 and resets again at 7/15/12 18:57:19, never getting beyond this time. If I set a different time the same kind of thing happens, resetting after a certain interval, not necessarily 19 seconds, but always resetting at an interval less than 5 minutes.
I have removed the battery to reset the RTC (the read then shows 0/0/0 0:0:80). I have replaced the battery just in case. I have downloaded the read program twice (in another, different example, the author reported that two sends were required to get the RTC to start properly).
I am left with the thought that a) there is some register set somewhere that is causing the RTC to act more as an interval timer than a RTC (but have found no documentation for such a register) or b) the RTC board is duff.
Before I contact the supplier has anyone any further thoughts as to anything I may have missed?
Regards,
Ric
I should add that the board is fitted with R2 and R3 which appear to be the required pull-up resistors for SDA and SCL. If I add additional 4K7 pull-ups the result is the same as without them. In other words: I don't think the pull-ups is the issue here.
