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-rw-r--r--quantum/split_common/i2c.c184
1 files changed, 0 insertions, 184 deletions
diff --git a/quantum/split_common/i2c.c b/quantum/split_common/i2c.c
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--- a/quantum/split_common/i2c.c
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1#include <util/twi.h>
2#include <avr/io.h>
3#include <stdlib.h>
4#include <avr/interrupt.h>
5#include <util/twi.h>
6#include <stdbool.h>
7#include "i2c.h"
8#include "split_flags.h"
9
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.
13//
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
17
18#define BUFFER_POS_INC() (slave_buffer_pos = (slave_buffer_pos+1)%SLAVE_BUFFER_SIZE)
19
20volatile uint8_t i2c_slave_buffer[SLAVE_BUFFER_SIZE];
21
22static volatile uint8_t slave_buffer_pos;
23static volatile bool slave_has_register_set = false;
24
25// Wait for an i2c operation to finish
26inline static
27void i2c_delay(void) {
28 uint16_t lim = 0;
29 while(!(TWCR & (1<<TWINT)) && lim < I2C_LOOP_TIMEOUT)
30 lim++;
31
32 // easier way, but will wait slightly longer
33 // _delay_us(100);
34}
35
36// Setup twi to run at 100kHz
37void i2c_master_init(void) {
38 // no prescaler
39 TWSR = 0;
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;
43}
44
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
48// 1 => error
49uint8_t i2c_master_start(uint8_t address) {
50 TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTA);
51
52 i2c_delay();
53
54 // check that we started successfully
55 if ( (TW_STATUS != TW_START) && (TW_STATUS != TW_REP_START))
56 return 1;
57
58 TWDR = address;
59 TWCR = (1<<TWINT) | (1<<TWEN);
60
61 i2c_delay();
62
63 if ( (TW_STATUS != TW_MT_SLA_ACK) && (TW_STATUS != TW_MR_SLA_ACK) )
64 return 1; // slave did not acknowledge
65 else
66 return 0; // success
67}
68
69
70// Finish the i2c transaction.
71void i2c_master_stop(void) {
72 TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO);
73
74 uint16_t lim = 0;
75 while(!(TWCR & (1<<TWSTO)) && lim < I2C_LOOP_TIMEOUT)
76 lim++;
77}
78
79// Write one byte to the i2c slave.
80// returns 0 => slave ACK
81// 1 => slave NACK
82uint8_t i2c_master_write(uint8_t data) {
83 TWDR = data;
84 TWCR = (1<<TWINT) | (1<<TWEN);
85
86 i2c_delay();
87
88 // check if the slave acknowledged us
89 return (TW_STATUS == TW_MT_DATA_ACK) ? 0 : 1;
90}
91
92uint8_t i2c_master_write_data(void *const TXdata, uint8_t dataLen) {
93
94 uint8_t *data = (uint8_t *)TXdata;
95 int err = 0;
96
97 for (int i = 0; i < dataLen; i++) {
98 err = i2c_master_write(data[i]);
99
100 if ( err )
101 return err;
102 }
103
104 return err;
105
106}
107
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
111uint8_t i2c_master_read(int ack) {
112 TWCR = (1<<TWINT) | (1<<TWEN) | (ack<<TWEA);
113
114 i2c_delay();
115 return TWDR;
116}
117
118void i2c_reset_state(void) {
119 TWCR = 0;
120}
121
122void i2c_slave_init(uint8_t address) {
123 TWAR = address << 0; // slave i2c address
124 // TWEN - twi enable
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);
129}
130
131ISR(TWI_vect);
132
133ISR(TWI_vect) {
134 uint8_t ack = 1;
135 switch(TW_STATUS) {
136 case TW_SR_SLA_ACK:
137 // this device has been addressed as a slave receiver
138 slave_has_register_set = false;
139 break;
140
141 case TW_SR_DATA_ACK:
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 ) {
151 ack = 0;
152 slave_buffer_pos = 0;
153 }
154
155 slave_has_register_set = true;
156 } else {
157 i2c_slave_buffer[slave_buffer_pos] = TWDR;
158
159 if ( slave_buffer_pos == I2C_BACKLIT_START) {
160 BACKLIT_DIRTY = true;
161 } else if ( slave_buffer_pos == (I2C_RGB_START+3)) {
162 RGB_DIRTY = true;
163 }
164
165 BUFFER_POS_INC();
166 }
167 break;
168
169 case TW_ST_SLA_ACK:
170 case TW_ST_DATA_ACK:
171 // master has addressed this device as a slave transmitter and is
172 // requesting data.
173 TWDR = i2c_slave_buffer[slave_buffer_pos];
174 BUFFER_POS_INC();
175 break;
176
177 case TW_BUS_ERROR: // something went wrong, reset twi state
178 TWCR = 0;
179 default:
180 break;
181 }
182 // Reset everything, so we are ready for the next TWI interrupt
183 TWCR |= (1<<TWIE) | (1<<TWINT) | (ack<<TWEA) | (1<<TWEN);
184}