I²C-Software RTC (DS1307)

[Frederik P. (frederikp)]

Hallo und gutem Middach,

ich habe für meinen PIC16F721 der kein MSSP hat, versucht eine 
Softwareimplementierung des I²C-Masters für den DS1307 zu programmieren. 
Bisher funktioniert sie jedoch nicht so, wie ich will, die RTC scheint 
überhaupt nicht zu reagieren.

Kann jemand von euch vielleicht kurz über den Code schauen, ob es 
irgendwelche Fehler gibt?

Danke im Voraus,
  Frederik

Anhang:

#include <htc.h>

#define SDA PORTBbits.RB4
#define SCL PORTBbits.RB6
#define SDA_OUT TRISBbits.TRISB4 = 0
#define SDA_IN TRISBbits.TRISB4 = 1
#define rtc_w 0b11010000
#define rtc_r 0b11010001

void wait(void);
void i2c_start(void);
void i2c_stop(void);
void i2c_readbit(void);
void i2c_writebit(void);
unsigned char i2c_read_ack(void);
unsigned char i2c_read_nack(void);
void i2c_write(unsigned char byte);
unsigned char rtc_read(unsigned char adress);
void rtc_write(unsigned char adress, unsigned char byte);

typedef struct
{
    unsigned temp1 :1;
    unsigned temp2 :1;
}Bit;

Bit temp;

void wait(void)
{
    char i;
    for (i = 0; i < 100; i++)
    {
        // NOP
    }
}

void i2c_start(void)
{
    SCL = 1;
    wait();
    SDA = 1;
    wait();
    SDA = 0;
    wait();
    SCL = 0;
}

void i2c_stop(void)
{
    SDA = 0;
    wait();
    SCL = 1;
    wait();
    SDA = 1;
}

void i2c_readbit(void)
{
    SDA_IN;
    SCL = 1;
    wait();
    temp.temp1 = SDA;
    wait();
    SCL = 0;
}

void i2c_writebit(void)
{
    SDA_OUT;
    SDA = temp.temp2;
    SCL = 1;
    wait();
    SCL = 0;
}

unsigned char i2c_read_ack(void)
{
    unsigned char byte = 0x00;
    unsigned char k;

    for (k = 0; k < 8; k++)
    {
        i2c_readbit();
        byte << 1;
        if (temp.temp1 == 0b1)
        {
            byte |= 0x01;
        }
        else
        {
            byte |= 0x00;
        }
    }

    temp.temp2 = 0;
    i2c_writebit();

    return byte;
}

unsigned char i2c_read_nack(void)
{
    unsigned char byte = 0x00;
    unsigned char k;

    for (k = 0; k < 8; k++)
    {
        i2c_readbit();
        byte << 1;
        if (temp.temp1 == 0b1)
        {
            byte |= 0x01;
        }
        else
        {
            byte |= 0x00;
        }
    }

    temp.temp2 = 1;
    i2c_writebit();

    return byte;
}

void i2c_write(unsigned char byte)
{
    unsigned char k;

    for (k = 0; k < 8; k++)
    {
        temp.temp2 = byte & 0x01;
        i2c_writebit();
        byte >> 1;
    }

    i2c_readbit();
}

unsigned char rtc_read(unsigned char adress)
{
    unsigned char byte;
    
    i2c_start();
    i2c_write(rtc_w);
    i2c_write(adress);
    i2c_stop();
    i2c_start();
    i2c_write(rtc_r);
    byte = i2c_read_nack();
    i2c_stop();

    return byte;
}

void rtc_write(unsigned char adress, unsigned char byte)
{
    i2c_start();
    i2c_write(rtc_w);
    i2c_write(adress);
    i2c_write(byte);
    i2c_stop();
}

[holger (Gast)]

>        byte >> 1;

        byte >>= 1;

Weiter oben ist

        byte << 1;

falsch.

[Frederik P. (frederikp)]

holger schrieb:
> Weiter oben ist
>
>         byte << 1;
>
> falsch.

Inwiefern falsch? Wie kann ich den Fehler beheben?

Danke, Frederik