4 #include <avr/interrupt.h>
8 #include "split_flags.h"
10 // Limits the amount of we wait for any one i2c transaction.
11 // Since were running SCL line 100kHz (=> 10μs/bit), and each transactions is
12 // 9 bits, a single transaction will take around 90μs to complete.
14 // (F_CPU/SCL_CLOCK) => # of μC cycles to transfer a bit
15 // poll loop takes at least 8 clock cycles to execute
16 #define I2C_LOOP_TIMEOUT (9+1)*(F_CPU/SCL_CLOCK)/8
18 #define BUFFER_POS_INC() (slave_buffer_pos = (slave_buffer_pos+1)%SLAVE_BUFFER_SIZE)
20 volatile uint8_t i2c_slave_buffer[SLAVE_BUFFER_SIZE];
22 static volatile uint8_t slave_buffer_pos;
23 static volatile bool slave_has_register_set = false;
25 // Wait for an i2c operation to finish
27 void i2c_delay(void) {
29 while(!(TWCR & (1<<TWINT)) && lim < I2C_LOOP_TIMEOUT)
32 // easier way, but will wait slightly longer
36 // Setup twi to run at 100kHz
37 void i2c_master_init(void) {
40 // Set TWI clock frequency to SCL_CLOCK. Need TWBR>10.
41 // Check datasheets for more info.
42 TWBR = ((F_CPU/SCL_CLOCK)-16)/2;
45 // Start a transaction with the given i2c slave address. The direction of the
46 // transfer is set with I2C_READ and I2C_WRITE.
47 // returns: 0 => success
49 uint8_t i2c_master_start(uint8_t address) {
50 TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTA);
54 // check that we started successfully
55 if ( (TW_STATUS != TW_START) && (TW_STATUS != TW_REP_START))
59 TWCR = (1<<TWINT) | (1<<TWEN);
63 if ( (TW_STATUS != TW_MT_SLA_ACK) && (TW_STATUS != TW_MR_SLA_ACK) )
64 return 1; // slave did not acknowledge
70 // Finish the i2c transaction.
71 void i2c_master_stop(void) {
72 TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO);
75 while(!(TWCR & (1<<TWSTO)) && lim < I2C_LOOP_TIMEOUT)
79 // Write one byte to the i2c slave.
80 // returns 0 => slave ACK
82 uint8_t i2c_master_write(uint8_t data) {
84 TWCR = (1<<TWINT) | (1<<TWEN);
88 // check if the slave acknowledged us
89 return (TW_STATUS == TW_MT_DATA_ACK) ? 0 : 1;
92 uint8_t i2c_master_write_data(void *const TXdata, uint8_t dataLen) {
94 uint8_t *data = (uint8_t *)TXdata;
97 for (int i = 0; i < dataLen; i++) {
98 err = i2c_master_write(data[i]);
108 // Read one byte from the i2c slave. If ack=1 the slave is acknowledged,
109 // if ack=0 the acknowledge bit is not set.
110 // returns: byte read from i2c device
111 uint8_t i2c_master_read(int ack) {
112 TWCR = (1<<TWINT) | (1<<TWEN) | (ack<<TWEA);
118 void i2c_reset_state(void) {
122 void i2c_slave_init(uint8_t address) {
123 TWAR = address << 0; // slave i2c address
125 // TWEA - enable address acknowledgement
126 // TWINT - twi interrupt flag
127 // TWIE - enable the twi interrupt
128 TWCR = (1<<TWIE) | (1<<TWEA) | (1<<TWINT) | (1<<TWEN);
137 // this device has been addressed as a slave receiver
138 slave_has_register_set = false;
142 // this device has received data as a slave receiver
143 // The first byte that we receive in this transaction sets the location
144 // of the read/write location of the slaves memory that it exposes over
145 // i2c. After that, bytes will be written at slave_buffer_pos, incrementing
146 // slave_buffer_pos after each write.
147 if(!slave_has_register_set) {
148 slave_buffer_pos = TWDR;
149 // don't acknowledge the master if this memory loctaion is out of bounds
150 if ( slave_buffer_pos >= SLAVE_BUFFER_SIZE ) {
152 slave_buffer_pos = 0;
155 slave_has_register_set = true;
157 i2c_slave_buffer[slave_buffer_pos] = TWDR;
159 if ( slave_buffer_pos == I2C_BACKLIT_START) {
160 BACKLIT_DIRTY = true;
161 } else if ( slave_buffer_pos == (I2C_RGB_START+3)) {
171 // master has addressed this device as a slave transmitter and is
173 TWDR = i2c_slave_buffer[slave_buffer_pos];
177 case TW_BUS_ERROR: // something went wrong, reset twi state
182 // Reset everything, so we are ready for the next TWI interrupt
183 TWCR |= (1<<TWIE) | (1<<TWINT) | (ack<<TWEA) | (1<<TWEN);