blob: 3edf85b12b4da79c991cc4f48eff27c8c5c124d5 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
|
/* 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);
}
}
|
