DS1307 and writing problem into 56 internal ram

retrolefty · March 5, 2013, 1:00am

Here are some simple functions I wrote to read and write the DS1307 RAM.

#define DS1307_ADDR 0x68
#define RAM_OFFSET 8         //map logical ram addresses (0-55) to physical addresses (8-63)

//write to DS1307 RAM where addr>=0 and addr<56
void dsSramWrite(byte addr, byte *values, byte nBytes)
{
    Wire.beginTransmission(DS1307_ADDR);
    Wire.write(addr + RAM_OFFSET);
    for (byte i=0; i<nBytes; i++) Wire.write(values[i]);
    Wire.endTransmission();    
}

//read from DS1307 RAM where addr>=0 and addr<56
void dsSramRead(byte addr, byte *values, byte nBytes)
{
    Wire.beginTransmission(DS1307_ADDR);
    Wire.write(addr + RAM_OFFSET);
    Wire.endTransmission();  
    Wire.requestFrom( (uint8_t)DS1307_ADDR, nBytes );
    for (byte i=0; i<nBytes; i++) values[i] = Wire.read();
}

//is the DS1307 oscillator running?
boolean dsIsRunning(void)
{
    byte secRegister;        //seconds register, bit 7 is clock halt (CH) bit
    
    Wire.beginTransmission(DS1307_ADDR);
    Wire.write(0x00);        //seconds register is address zero
    Wire.endTransmission();  
    Wire.requestFrom( DS1307_ADDR, 1 );
    secRegister = Wire.read();
    
    return !(secRegister & 0x80);
}

Neat functions. What is the purpose of the isrunning function? Must the RTC clock be stopped to write (or read) into the scratch pad ram locations?

Lefty

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DS1307 and writing problem into 56 internal ram

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