int main (void)
{
m_clockdivide(0);
twi_init(I2C_ADDR);
while(1)
{
if (receive_done)
{
process_command();
receive_done = false;
TWI_ACK();
}
}
}
void twi_overflow_irq(void)
#endif
{
#if INTERRUPTS
uint8_t sreg;
#endif
uint8_t buf = USIDR;
switch(twidriver.state){
case TWI_START:
/* clear overflow bit counter */
USISR &= ~((1<<USICNT0)|(1<<USICNT1)|(1<<USICNT2)|(1<<USICNT3));
twidriver.state = TWI_ADDR;
break;
case TWI_ADDR:
/* message for this device... */
if( ((buf & 0xfe) == twidriver.addr)
#if (BUILD_VERSION > 0)
||((buf & 0xfe) == TWIADDR_BROADCAST)
||( (twidriver.addr < TWIADDR_FLIGHT_START) &&
((buf & 0xfe) == (twidriver.addr+TWIADDR_FLIGHT_START)))
#endif
){
/* if reading, something needs to be ready in the buffer */
if(buf & 0x1){
#if (BUILD_VERSION > 0)
/* flight protocol */
if((buf & 0xfe) != twidriver.addr){
#if INTERRUPTS
USICR &= ~(1<<USISIE);
sreg = SREG;
sei();
#endif
usr_process();
#if INTERRUPTS
cli();
SREG = sreg;
USICR |= (1<<USISIE);
#endif
}
else
#endif
/* host protocol */
if(!twidriver.size){
TWI_NACK();
break;
}
}
/* remember cmd byte and zero the length counter */
twidriver.cmd = buf;
twidriver.inlen = twidriver.outlen = 0;
/* do an /ACK; */
TWI_ACK();
}
/* message for some other device */
else{
TWI_NACK();
}
break;
/* just read the ACK bit from master... */
case TWI_TX_ACK:
/* master did not /ACK */
if(twidriver.outlen && (buf & 0x1)){
TWI_NACK();
}
/* master /ACKed */
else{
TWI_DDR |= (1<<SDA_PIN);
/* load next byte or handle overflow */
if(twidriver.outlen < twidriver.size)
USIDR = twidriver.data[twidriver.outlen++];
else
USIDR = 0x55;
twidriver.state = TWI_TX;
}
break;
/* just sent the ACK bit to master... */
case TWI_RX_ACK:
TWI_DDR &= ~(1<<SDA_PIN);
twidriver.state = TWI_RX;
break;
/* master is writing to the buffer */
case TWI_RX:
/* buffer if there is space */
if(twidriver.inlen < TWI_BUFSIZE){
twidriver.data[twidriver.inlen++] = buf;
TWI_ACK();
}
/* give up if master overruns */
else{
TWI_NACK();
}
break;
/* master is reading from the buffer */
case TWI_TX:
TWI_GET_ACK();
break;
default:
break;
}
USISR |= (1<<USIOIF); /* clear overflow flag */
}
