Schaltung:
http://ourworld.compuserve.com/homepages/Dominique_CHARLET/8051.gif
(i2c - im Bild links unten)
habs auch ohne widerstände versucht.... keine Chance etwas
einzulesen... kein ACK, nix...
Source:
#ifndef READ
#define READ 1
#endif
#ifndef WRITE
#define WRITE 0
#endif
#ifndef I2CCLK
#define I2CCLK 0xA0
#endif
#ifndef SCL
static bit SCL @ 0x96;
#endif
#ifndef SDA
static bit SDA @ 0x97;
#endif
unsigned char _i2c_error; // bit array of error types
void _I2CBitDly(void);
void _I2CSCLHigh(void);
void I2CSendAddr(unsigned char addr, unsigned char rd);
void I2CSendByte(unsigned char bt);
unsigned char _I2CGetByte(unsigned char lastone);
void I2CSendStop(void);
#define I2CGetByte() _I2CGetByte(0)
#define I2CGetLastByte() _I2CGetByte(1)
void _I2CBitDly(void) // wait 4.7uS, or thereabouts
{ // tune to xtal. This works at
11.0592MHz
asm(" NOP"); // delay is 5.4uS, only 4.3uS without
return;
}
void _I2CSCLHigh(void) // set SCL high, and wait for it to go
high
{
register int err;
SCL = 1;
while (! SCL)
{
err++;
if (!err)
{
_i2c_error &= 0x02; // SCL stuck, something's holding it
down
return;
}
}
}
void I2CSendAddr(unsigned char addr, unsigned char rd)
{
SCL = 1;
_I2CBitDly();
SDA = 0; // generate start
_I2CBitDly();
SCL = 0;
_I2CBitDly();
I2CSendByte(addr+rd); // send address byte
}
void I2CSendByte(unsigned char bt)
{
register unsigned char i;
for (i=0; i<8; i++)
{
if (bt & 0x80) SDA = 1; // send each bit, MSB first
else SDA = 0;
_I2CSCLHigh();
_I2CBitDly();
SCL = 0;
_I2CBitDly();
bt = bt << 1;
}
SDA = 1; // listen for ACK
_I2CSCLHigh();
_I2CBitDly();
if (SDA)
_i2c_error &= 0x01; // ack didn't happen, may be nothing
out there
SCL = 0;
_I2CBitDly();
}
unsigned char _I2CGetByte(unsigned char lastone) // lastone == 1 for
last byte
{
register unsigned char i, res;
res = 0;
for (i=0;i<8;i++) // each bit at a time, MSB first
{
_I2CSCLHigh();
_I2CBitDly();
res *= 2;
if (SDA) res++;
SCL = 0;
_I2CBitDly();
}
SDA = lastone; // send ACK according to 'lastone'
_I2CSCLHigh();
_I2CBitDly();
SCL = 0;
SDA = 1;
_I2CBitDly();
return(res);
}
void I2CSendStop(void)
{
SDA = 0;
_I2CBitDly();
_I2CSCLHigh();
_I2CBitDly();
SDA = 1;
_I2CBitDly();
}
// test code
//void main(void)
//{
// unsigned char b;
// I2CSendAddr(1,WRITE);
// I2CSendByte(0);
// I2CSendStop();
// I2CSendAddr(1,READ);
// b = I2CGetByte();
// b = I2CGetLastByte();
// I2CSendStop();
//}
/
