101 lines
2.8 KiB
C
101 lines
2.8 KiB
C
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/* Library made by: g4lvanix
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* Github repository: https://github.com/g4lvanix/I2C-slave-lib
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*/
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#include <avr/io.h>
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#include <util/twi.h>
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#include <avr/interrupt.h>
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#include "i2c_slave.h"
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void i2c_init(uint8_t address){
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// load address into TWI address register
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TWAR = (address << 1);
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// set the TWCR to enable address matching and enable TWI, clear TWINT, enable TWI interrupt
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TWCR = (1<<TWIE) | (1<<TWEA) | (1<<TWINT) | (1<<TWEN);
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}
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void i2c_stop(void){
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// clear acknowledge and enable bits
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TWCR &= ~( (1<<TWEA) | (1<<TWEN) );
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}
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ISR(TWI_vect){
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// temporary stores the received data
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uint8_t data;
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// own address has been acknowledged
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if( (TWSR & 0xF8) == TW_SR_SLA_ACK ){
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buffer_address = 0xFF;
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// clear TWI interrupt flag, prepare to receive next byte and acknowledge
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TWCR |= (1<<TWIE) | (1<<TWINT) | (1<<TWEA) | (1<<TWEN);
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}
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else if( (TWSR & 0xF8) == TW_SR_DATA_ACK ){ // data has been received in slave receiver mode
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// save the received byte inside data
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data = TWDR;
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// check wether an address has already been transmitted or not
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if(buffer_address == 0xFF){
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buffer_address = data;
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// clear TWI interrupt flag, prepare to receive next byte and acknowledge
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TWCR |= (1<<TWIE) | (1<<TWINT) | (1<<TWEA) | (1<<TWEN);
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}
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else{ // if a databyte has already been received
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// store the data at the current address
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rxbuffer[buffer_address] = data;
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// increment the buffer address
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buffer_address++;
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// if there is still enough space inside the buffer
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if(buffer_address < 0xFF){
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// clear TWI interrupt flag, prepare to receive next byte and acknowledge
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TWCR |= (1<<TWIE) | (1<<TWINT) | (1<<TWEA) | (1<<TWEN);
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}
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else{
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// Don't acknowledge
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TWCR &= ~(1<<TWEA);
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// clear TWI interrupt flag, prepare to receive last byte.
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TWCR |= (1<<TWIE) | (1<<TWINT) | (1<<TWEN);
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}
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}
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}
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else if( (TWSR & 0xF8) == TW_ST_DATA_ACK ){ // device has been addressed to be a transmitter
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// copy data from TWDR to the temporary memory
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data = TWDR;
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// if no buffer read address has been sent yet
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if( buffer_address == 0xFF ){
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buffer_address = data;
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}
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// copy the specified buffer address into the TWDR register for transmission
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TWDR = txbuffer[buffer_address];
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// increment buffer read address
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buffer_address++;
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// if there is another buffer address that can be sent
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if(buffer_address < 0xFF){
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// clear TWI interrupt flag, prepare to send next byte and receive acknowledge
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TWCR |= (1<<TWIE) | (1<<TWINT) | (1<<TWEA) | (1<<TWEN);
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}
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else{
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// Don't acknowledge
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TWCR &= ~(1<<TWEA);
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// clear TWI interrupt flag, prepare to receive last byte.
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TWCR |= (1<<TWIE) | (1<<TWINT) | (1<<TWEN);
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}
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}
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else{
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// if none of the above apply prepare TWI to be addressed again
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TWCR |= (1<<TWIE) | (1<<TWEA) | (1<<TWEN);
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}
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}
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