1 /* Library made by: g4lvanix
2 * Github repository: https://github.com/g4lvanix/I2C-slave-lib
7 #include <avr/interrupt.h>
10 #include "i2c_slave.h"
12 void i2c_init(uint8_t address){
13 // load address into TWI address register
14 TWAR = (address << 1);
15 // set the TWCR to enable address matching and enable TWI, clear TWINT, enable TWI interrupt
16 TWCR = (1 << TWIE) | (1 << TWEA) | (1 << TWINT) | (1 << TWEN);
20 // clear acknowledge and enable bits
21 TWCR &= ~((1 << TWEA) | (1 << TWEN));
26 // temporary stores the received data
31 // The device is now a slave receiver
32 slave_has_register_set = false;
36 // This device is a slave receiver and has received data
37 // First byte is the location then the bytes will be writen in buffer with auto-incriment
38 if(!slave_has_register_set){
39 buffer_address = TWDR;
41 if (buffer_address >= RX_BUFFER_SIZE){ // address out of bounds dont ack
45 slave_has_register_set = true; // address has been receaved now fill in buffer
47 rxbuffer[buffer_address] = TWDR;
54 // This device is a slave transmitter and master has requested data
55 TWDR = txbuffer[buffer_address];
60 // We got an error, reset i2c
66 // Reset i2c state mahcine to be ready for next interrupt
67 TWCR |= (1 << TWIE) | (1 << TWINT) | (ack << TWEA) | (1 << TWEN);