mirror of
https://github.com/qmk/qmk_firmware.git
synced 2024-11-22 11:29:26 +00:00
101 lines
2.8 KiB
C
Executable File
101 lines
2.8 KiB
C
Executable File
/* Library made by: g4lvanix
|
|
* Github repository: https://github.com/g4lvanix/I2C-slave-lib
|
|
*/
|
|
|
|
#include <avr/io.h>
|
|
#include <util/twi.h>
|
|
#include <avr/interrupt.h>
|
|
|
|
#include "i2c_slave.h"
|
|
|
|
void i2c_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_stop(void){
|
|
// clear acknowledge and enable bits
|
|
TWCR &= ~( (1<<TWEA) | (1<<TWEN) );
|
|
}
|
|
|
|
ISR(TWI_vect){
|
|
|
|
// temporary stores the received data
|
|
uint8_t data;
|
|
|
|
// own address has been acknowledged
|
|
if( (TWSR & 0xF8) == TW_SR_SLA_ACK ){
|
|
buffer_address = 0xFF;
|
|
// clear TWI interrupt flag, prepare to receive next byte and acknowledge
|
|
TWCR |= (1<<TWIE) | (1<<TWINT) | (1<<TWEA) | (1<<TWEN);
|
|
}
|
|
else if( (TWSR & 0xF8) == TW_SR_DATA_ACK ){ // data has been received in slave receiver mode
|
|
|
|
// save the received byte inside data
|
|
data = TWDR;
|
|
|
|
// check wether an address has already been transmitted or not
|
|
if(buffer_address == 0xFF){
|
|
|
|
buffer_address = data;
|
|
|
|
// clear TWI interrupt flag, prepare to receive next byte and acknowledge
|
|
TWCR |= (1<<TWIE) | (1<<TWINT) | (1<<TWEA) | (1<<TWEN);
|
|
}
|
|
else{ // if a databyte has already been received
|
|
|
|
// store the data at the current address
|
|
rxbuffer[buffer_address] = data;
|
|
|
|
// increment the buffer address
|
|
buffer_address++;
|
|
|
|
// if there is still enough space inside the buffer
|
|
if(buffer_address < 0xFF){
|
|
// clear TWI interrupt flag, prepare to receive next byte and acknowledge
|
|
TWCR |= (1<<TWIE) | (1<<TWINT) | (1<<TWEA) | (1<<TWEN);
|
|
}
|
|
else{
|
|
// Don't acknowledge
|
|
TWCR &= ~(1<<TWEA);
|
|
// clear TWI interrupt flag, prepare to receive last byte.
|
|
TWCR |= (1<<TWIE) | (1<<TWINT) | (1<<TWEN);
|
|
}
|
|
}
|
|
}
|
|
else if( (TWSR & 0xF8) == TW_ST_DATA_ACK ){ // device has been addressed to be a transmitter
|
|
|
|
// copy data from TWDR to the temporary memory
|
|
data = TWDR;
|
|
|
|
// if no buffer read address has been sent yet
|
|
if( buffer_address == 0xFF ){
|
|
buffer_address = data;
|
|
}
|
|
|
|
// copy the specified buffer address into the TWDR register for transmission
|
|
TWDR = txbuffer[buffer_address];
|
|
// increment buffer read address
|
|
buffer_address++;
|
|
|
|
// if there is another buffer address that can be sent
|
|
if(buffer_address < 0xFF){
|
|
// clear TWI interrupt flag, prepare to send next byte and receive acknowledge
|
|
TWCR |= (1<<TWIE) | (1<<TWINT) | (1<<TWEA) | (1<<TWEN);
|
|
}
|
|
else{
|
|
// Don't acknowledge
|
|
TWCR &= ~(1<<TWEA);
|
|
// clear TWI interrupt flag, prepare to receive last byte.
|
|
TWCR |= (1<<TWIE) | (1<<TWINT) | (1<<TWEN);
|
|
}
|
|
|
|
}
|
|
else{
|
|
// if none of the above apply prepare TWI to be addressed again
|
|
TWCR |= (1<<TWIE) | (1<<TWEA) | (1<<TWEN);
|
|
}
|
|
}
|