[En-Nut-Discussion] TWI / I2C and DS1307

[Douglas Pearless]

Thanks to the people who have sent me code...

I have persevered with the TWI code that is part of NUTO/S

I have:

#define RTC_I2C_ADDRESS 0x68 // this is first 7 bits the address of the 
// remembering it gets shifted one bit to the left to make it 0xD0
//for the maxim DS1307 RTC

...

      TwInit(128);
	fprintf(uart0, "\n\rTwInit RC = %d\n", TwMasterError());
      fflush(uart0);
	TWI_speed = 100000;
	TwIOCtl(TWI_SETSPEED,&TWI_speed);
	fprintf(uart0, "\n\rTWI_SETSPEED RC = %u\n", TwMasterError());
      fflush(uart0);
	// init RTC
	initRTC((u_char)RTC_I2C_ADDRESS);
	fprintf(uart0, "\n\rinitrtc RC = %d\n", TwMasterError());
      fflush(uart0);
	NutDelay(2000);
	getRTCtime((u_char)RTC_I2C_ADDRESS);
 	fprintf(uart0, "\n\rgetRTCtime RC = %d\n", TwMasterError());
      fflush(uart0);

and

int readRTC(u_char sla,u_int addr,void *rxxdata,u_short len)
{

   u_char adata[1];

   adata[0] = (u_char) addr;
   return TwMasterTransact(sla, adata, 1,rxxdata, len, 0);
}

int writeRTC(u_char sla,u_int addr,void *txdata,u_short len)
{  
   u_char data[17];

   data[0] = (u_char)(addr);
   memcpy(&data[1],txdata,len);
   return TwMasterTransact(sla, data,len+1, 0, 0, 0);
}

int initRTC(u_char sla)
{
   /* DS1307
	*/
	u_char data[12];  //yes an array of 1 is redundant, but I want
consistency
	int rc;
	
	data[0] = 0b00000000; //bit =0 to start oscillator, zero minutes
	data[1] = 0b00000000; // zero minutes
	data[2] = 0b00100000; //24hour mode, 8pm
	data[3] = 0b00000100; //day 6 (Saturday)
	data[4] = 0b00000001; //1st
	data[5] = 0b00000001; //January
	data[6] = 0b00000101; //2005
    data[7] = 0b00010000; //turn on the square wave
	data[8] = 'A';
	data[9] = 'B';
	data[10]= 'C';
	data[11]='D';
	rc = writeRTC(sla,0,data,12);
    return rc;
}

int getRTCtime(u_char sla)
{
    u_char data[12];
	int rc;
	
	data[0] = 0b00000000;
	data[1] = 0b00000000;
	data[2] = 0b00000000;
	data[3] = 0b00000000;
	data[4] = 0b00000000;
	data[5] = 0b00000000;
	data[6] = 0b00000000;
    data[7] = 0b00000000;
    data[8] = 0b00000000;
    data[9] = 0b00000000;
    data[10] = 0b00000000;
    data[11] = 0b00000000;
	rc = readRTC(sla,0,&data,12);
   return rc;
}

On UART0 I get:

TwInit RC = 0
TWI_SETSPEED RC = 0
initrtc RC = 0
getRTCtime RC = 0

and in AVRStudio, the getRTCtime always returns "data" as being:

data[0] = 0x00
data[1] = 0x80
data[2] = 0x00
data[3] = 0x82
data[4] = 0x88
data[5] = 0x0C
data[6] = 0x40
data[7] = 0x80
data[8] = 0x20
data[9] = 0x00
data[10] = 0x12
data[11] = 0x00


I can see pulses on the SDA and SCL lines, but I always get the same garbage
back.

Note that data[8] through data[11] are RAM locations.

Any ideas??

Cheers Douglas


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