universal software i2c for microcontrollers

softi2c.c

// example for xmega256d3

// bit delay
static void delay(void) {
    __no_operation();
    __no_operation();
    __no_operation();
    __no_operation();
    __no_operation();
    __no_operation();
    __no_operation();
    __no_operation();
    __no_operation();
    __no_operation();   
}

// Basefunctions

// set SDA Pin to value (0 or 1)
static void setSDA(uint8_t value) {
    if (value)
        PORTE.OUTSET =  1;
    else
        PORTE.OUTCLR =  1;
}

// set SCL Pin to value (0 or 1)
static void setSCL(uint8_t value) {
    if (value)
        PORTE.OUTSET =  2;
    else
        PORTE.OUTCLR =  2;
}

// configure SDA Pin as Input
static void setREAD(void) {
    PORTE.DIRCLR = 1;
    PORTE.OUTCLR = 1;
}

// configure SDA Pin as OUTPUT
static void setWRITE(void) {
    PORTE.DIRSET = 1;
}

// read SDA Pin
static uint8_t readSDA(void) {
    return PORTE.IN & 1;
}

// higher level functions

// send Startcondition
void i2cSoft_Start() {
     setSDA(1);
     setWRITE();
     setSCL(1);
     delay();
     setSDA(0);
     delay();
     setSCL(0);
     delay();
}

// send Stopcondition
void i2cSoft_Stop() {
     setWRITE();
     setSCL(0);
     setSDA(0);
     delay();
     setSCL(1);
     delay();
     delay();
     setSDA(1);
     delay();
     setREAD();
}

// write ic2 address or data and returns a recieved ack
uint8_t i2cSoft_Write(uint8_t data) {
    uint8_t index;
    setWRITE();
    for (index = 0; index < 8; index++) {
        setSCL(0);
        setSDA(data & 0x80);
        delay(); 
        setSCL(1);
        delay();
        data <<= 1;
    }
    setSCL(0);
    delay();
    setREAD();
    __no_operation();
    __no_operation();
    setSCL(1);
    delay();
    index = readSDA();
    __no_operation();
    __no_operation();
    setSCL(0);    
    return index;
}

// read ic2 data with or without acknoglege depending on ack
uint8_t i2cSoft_Read(uint8_t ack) {
  uint8_t i;
  uint16_t data = 0;  
  setREAD();
  setSDA(0);
  for (i = 0; i < 8; i++) {
     setSCL(1);
     data <<= 1;
     data |= readSDA();
     delay();
     setSCL(0);
     delay();
  }
  setWRITE();
  setSDA(!ack);
  __no_operation();
  __no_operation(); 
  setSCL(1);
  delay();
  setSCL(0);
  delay();
  setSDA(0);
  return data;
}