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 volatile uint8_t i2c_slave_reg[I2C_SLAVE_REG_COUNT];
14 static volatile uint8_t buffer_address;
15 static volatile bool slave_has_register_set = false;
17 void i2c_slave_init(uint8_t address){
18 // load address into TWI address register
20 // set the TWCR to enable address matching and enable TWI, clear TWINT, enable TWI interrupt
21 TWCR = (1 << TWIE) | (1 << TWEA) | (1 << TWINT) | (1 << TWEN);
24 void i2c_slave_stop(void){
25 // clear acknowledge and enable bits
26 TWCR &= ~((1 << TWEA) | (1 << TWEN));
34 // The device is now a slave receiver
35 slave_has_register_set = false;
39 // This device is a slave receiver and has received data
40 // First byte is the location then the bytes will be writen in buffer with auto-incriment
41 if(!slave_has_register_set){
42 buffer_address = TWDR;
44 if (buffer_address >= I2C_SLAVE_REG_COUNT) { // address out of bounds dont ack
48 slave_has_register_set = true; // address has been receaved now fill in buffer
50 i2c_slave_reg[buffer_address] = TWDR;
57 // This device is a slave transmitter and master has requested data
58 TWDR = i2c_slave_reg[buffer_address];
63 // We got an error, reset i2c
69 // Reset i2c state machine to be ready for next interrupt
70 TWCR |= (1 << TWIE) | (1 << TWINT) | (ack << TWEA) | (1 << TWEN);