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use 20kHz as I2C frequency
[rsbs2] / bmc / i2c.c
1 #include <util/twi.h>
2 #include <avr/interrupt.h>
3 #include <stdio.h>
4 #include "i2c.h"
5 #include "bmc.h"
6 #include "ipmb.h"
7
8 #define TWCR_ACK TWCR = (1<<TWEN)|(1<<TWIE)|(1<<TWINT)|(1<<TWEA)|(0<<TWSTA)|(0<<TWSTO)|(0<<TWWC);
9 #define TWCR_NACK TWCR = (1<<TWEN)|(1<<TWIE)|(1<<TWINT)|(0<<TWEA)|(0<<TWSTA)|(0<<TWSTO)|(0<<TWWC);
10 #define TWCR_RESET TWCR = (1<<TWEN)|(1<<TWIE)|(1<<TWINT)|(1<<TWEA)|(0<<TWSTA)|(1<<TWSTO)|(0<<TWWC);
11
12 volatile unsigned char i2c_databuf[24];
13 volatile uint8_t i2c_len = 0x00;
14 static volatile uint8_t i2c_pos = 0x00;
15 volatile uint8_t i2c_done = 0x00;
16
17 #define I2C_FREQ 20000UL
18
19 void i2c_init()
20 {
21 /* SCLf = F_CPU / (16 + 2 * TWBR * 4^TWPS)
22 * TWPS is 0 =>
23 * TWBR = (F_CPU/(2 * SCL)) - 8
24 */
25 TWBR = (F_CPU/(2*I2C_FREQ))-8;
26 TWAR = BMC_ADDR & 0xfe;
27 TWDR = 0x00;
28 TWCR &= ~((1<<TWSTA) | (1<<TWSTO));
29 TWCR |= ((1<<TWEA) | (1<<TWEN) | (1<<TWIE));
30 #ifdef __AVR_ATmega16__
31 PORTC = 0x03;
32 #else
33 #error "Don't know how to set pullups for this chip, please add support"
34 #endif
35 }
36
37 void i2c_send(unsigned char *buf, int len)
38 {
39 uint8_t old_TWCR = TWCR;
40 uint8_t old_SREG = SREG;
41 int i;
42
43 cli();
44
45 TWCR = ((1<<TWINT) | (1<<TWSTA) | (1<<TWEN)); /* Send start */
46
47 while(!(TWCR & (1<<TWINT))) {}
48 if (TW_STATUS != TW_START) {
49 #ifdef DEBUG
50 printf("I2C: error sending START\n");
51 #endif
52 goto out;
53 }
54
55 TWDR = buf[0]; /* SLA_W */
56 TWCR = ((1<<TWINT) | (1<<TWEN));
57
58 while(!(TWCR & (1<<TWINT))) {}
59 if (TW_STATUS != TW_MT_SLA_ACK) {
60 #ifdef DEBUG
61 printf("I2C: error sending SLA_W\n");
62 #endif
63 goto out2;
64 }
65
66 for(i = 1; i < len; i++) {
67 TWDR = buf[i]; /* Send Data */
68 TWCR = ((1<<TWINT) | (1<<TWEN));
69
70 while(!(TWCR & (1<<TWINT))) {}
71 if (TW_STATUS != TW_MT_DATA_ACK) {
72 #ifdef DEBUG
73 printf("I2C: error sending DATA byte %d\n", i);
74 #endif
75 goto out2;
76 }
77 }
78
79 #ifdef DEBUG
80 printf("I2C Data sent\n");
81 #endif
82
83 out2:
84 TWCR = ((1<<TWINT) | (1<<TWEN) | (1<<TWSTO));
85 while(TWCR & (1<<TWSTO)) {}
86
87 out:
88 SREG = old_SREG;
89 TWCR = old_TWCR | (1<<TWINT);
90 }
91
92 ISR (TWI_vect, ISR_BLOCK)
93 {
94 if (i2c_done)
95 TWCR_RESET;
96
97 switch (TW_STATUS) {
98 case TW_SR_SLA_ACK:
99 #ifdef DEBUG
100 printf("I2C: Slave 0x%02x adressed\n", TWDR);
101 #endif
102 i2c_pos = 0x00;
103 i2c_databuf[i2c_pos] = TWDR;
104 i2c_pos++;
105 TWCR_ACK;
106 break;
107
108 case TW_SR_DATA_ACK:
109 #ifdef DEBUG
110 printf("I2C: Data received: 0x%02x\n", TWDR);
111 #endif
112 if (i2c_pos >= sizeof(i2c_databuf)) {
113 TWCR_RESET;
114 i2c_pos = 0x00;
115 break;
116 }
117 i2c_databuf[i2c_pos] = TWDR;
118 i2c_pos++;
119 TWCR_ACK;
120 break;
121
122 case TW_SR_STOP:
123 #ifdef DEBUG
124 printf("I2C: STOP received\n");
125 #endif
126 i2c_len = i2c_pos;
127 i2c_pos = 0x00;
128 i2c_done = 0x01;
129 TWCR_RESET;
130 break;
131
132 case TW_NO_INFO:
133 #ifdef DEBUG
134 printf("I2C: TW_NO_INFO received status 0x%2x\n", TW_STATUS);
135 #endif
136 TWCR |= (1<<TWINT);
137 break;
138
139 default:
140 #ifdef DEBUG
141 printf("I2C: Unimplemented status 0x%02x\n", TW_STATUS);
142 #endif
143 TWCR_RESET;
144 break;
145 }
146 }
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