/* Library made by: g4lvanix * Github repository: https://github.com/g4lvanix/I2C-slave-lib */ #include #include #include #include #include "i2c_slave.h" volatile uint8_t i2c_slave_reg[I2C_SLAVE_REG_COUNT]; static volatile uint8_t buffer_address; static volatile bool slave_has_register_set = false; void i2c_slave_init(uint8_t address){ // load address into TWI address register TWAR = (address << 1); // set the TWCR to enable address matching and enable TWI, clear TWINT, enable TWI interrupt TWCR = (1 << TWIE) | (1 << TWEA) | (1 << TWINT) | (1 << TWEN); } void i2c_slave_stop(void){ // clear acknowledge and enable bits TWCR &= ~((1 << TWEA) | (1 << TWEN)); } ISR(TWI_vect){ uint8_t ack = 1; switch(TW_STATUS){ case TW_SR_SLA_ACK: // The device is now a slave receiver slave_has_register_set = false; break; case TW_SR_DATA_ACK: // This device is a slave receiver and has received data // First byte is the location then the bytes will be writen in buffer with auto-incriment if(!slave_has_register_set){ buffer_address = TWDR; if (buffer_address >= I2C_SLAVE_REG_COUNT) { // address out of bounds dont ack ack = 0; buffer_address = 0; } slave_has_register_set = true; // address has been receaved now fill in buffer } else { i2c_slave_reg[buffer_address] = TWDR; buffer_address++; } break; case TW_ST_SLA_ACK: case TW_ST_DATA_ACK: // This device is a slave transmitter and master has requested data TWDR = i2c_slave_reg[buffer_address]; buffer_address++; break; case TW_BUS_ERROR: // We got an error, reset i2c TWCR = 0; default: break; } // Reset i2c state machine to be ready for next interrupt TWCR |= (1 << TWIE) | (1 << TWINT) | (ack << TWEA) | (1 << TWEN); }