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1 | 241 | bcoltin | /**
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2 | * Copyright (c) 2007 Colony Project
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3 | *
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4 | * Permission is hereby granted, free of charge, to any person
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5 | * obtaining a copy of this software and associated documentation
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6 | * files (the "Software"), to deal in the Software without
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7 | * restriction, including without limitation the rights to use,
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8 | * copy, modify, merge, publish, distribute, sublicense, and/or sell
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9 | * copies of the Software, and to permit persons to whom the
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10 | * Software is furnished to do so, subject to the following
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11 | * conditions:
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12 | *
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13 | * The above copyright notice and this permission notice shall be
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14 | * included in all copies or substantial portions of the Software.
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15 | *
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16 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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17 | * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
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18 | * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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19 | * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
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20 | * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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21 | * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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22 | * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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23 | * OTHER DEALINGS IN THE SOFTWARE.
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24 | **/
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25 | |||
26 | |||
27 | /**
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28 | * @file i2c.c
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29 | * @brief Implemenation of I2C communications protocol
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30 | *
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31 | 54 | kwoo | * In the case where you have master sends and then a master request to the same
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32 | * address, you will not give up control of the line because the send and
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33 | 78 | kwoo | * request addresses are seen as different addresses. In between it will send a
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34 | 54 | kwoo | * restart but will not give up the line.
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35 | *
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36 | 78 | kwoo | * @author CMU Robotics Club, Kevin Woo, Sursh Nidhiry
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37 | 54 | kwoo | * @bug Not tested.
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38 | */
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39 | |||
40 | #include <avr/interrupt.h> |
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41 | #include <util/twi.h> |
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42 | |||
43 | #include "i2c.h" |
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44 | #include "ring_buffer.h" |
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45 | |||
46 | 70 | kwoo | |
47 | /**
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48 | * @brief Set bit rate 12 = 100kbit/s (max speed setting is 10 for an
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49 | 54 | kwoo | * 8 MHz clock). It is a divider, so the lower the number the faster the speed.
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50 | */
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51 | #define I2C_BIT_RATE_DIVIDER 0x0C |
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52 | |||
53 | static int start_flag; |
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54 | |||
55 | static fun_mrecv_t master_recv_function;
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56 | static fun_srecv_t slave_recv_function;
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57 | static fun_send_t slave_send_function;
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58 | |||
59 | RING_BUFFER_NEW(i2c_buffer, 128, char, i2c_write_buff, i2c_addr_buff); |
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60 | |||
61 | 70 | kwoo | |
62 | 54 | kwoo | int i2c_init(char addr, fun_mrecv_t master_recv, fun_srecv_t slave_recv, fun_send_t slave_send) { |
63 | 78 | kwoo | master_recv_function = master_recv; |
64 | slave_recv_function = slave_recv; |
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65 | slave_send_function = slave_send; |
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66 | 54 | kwoo | |
67 | 78 | kwoo | RING_BUFFER_CLEAR(i2c_write_buff); |
68 | RING_BUFFER_CLEAR(i2c_addr_buff); |
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69 | 54 | kwoo | |
70 | 78 | kwoo | /* enables twi interrupt, automatic ack sending, and all twi hardware */
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71 | TWCR = (_BV(TWEA) | _BV(TWEN) | _BV(TWIE)); |
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72 | 54 | kwoo | |
73 | 78 | kwoo | /* sets the bit rate of data transmission */
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74 | TWBR = I2C_BIT_RATE_DIVIDER; |
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75 | 54 | kwoo | |
76 | 78 | kwoo | /* sets the address (it is stored in the 7 most significant bits) and allows
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77 | * global messages to be accepted */
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78 | TWAR = (addr << 1) | 1; |
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79 | 54 | kwoo | |
80 | 78 | kwoo | return 0; |
81 | 54 | kwoo | } |
82 | |||
83 | int i2c_send(char dest, char *data, size_t bytes) { |
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84 | 78 | kwoo | int i;
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85 | 54 | kwoo | |
86 | 78 | kwoo | /* adding data to be sent to ring buffers is not atomic,
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87 | * so disable interrupts */
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88 | cli(); |
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89 | for(i = 0; i < bytes; i++) { |
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90 | if(RING_BUFFER_FULL(i2c_write_buff)) {
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91 | sei(); |
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92 | return -1; |
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93 | } |
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94 | |||
95 | RING_BUFFER_ADD(i2c_write_buff, data[i]); |
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96 | RING_BUFFER_ADD(i2c_addr_buff, dest << 1);
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97 | 54 | kwoo | } |
98 | |||
99 | 78 | kwoo | /* re-enable the interrupts */
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100 | sei(); |
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101 | |||
102 | /* send the start bit, only if this device is not currently master */
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103 | if(!start_flag) {
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104 | start_flag = 1;
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105 | TWCR |= _BV(TWSTA); |
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106 | TWCR |= _BV(TWINT); |
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107 | } |
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108 | 54 | kwoo | |
109 | 78 | kwoo | return 0; |
110 | 54 | kwoo | } |
111 | |||
112 | int i2c_request(char dest) { |
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113 | 78 | kwoo | if(RING_BUFFER_FULL(i2c_write_buff))
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114 | return -1; |
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115 | 54 | kwoo | |
116 | 78 | kwoo | RING_BUFFER_ADD(i2c_write_buff, 0);
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117 | RING_BUFFER_ADD(i2c_addr_buff, (dest << 1) | 1); |
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118 | 54 | kwoo | |
119 | 78 | kwoo | if(!start_flag) {
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120 | start_flag = 1;
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121 | TWCR |= _BV(TWSTA); |
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122 | TWCR |= _BV(TWINT); |
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123 | } |
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124 | 54 | kwoo | |
125 | 78 | kwoo | return 0; |
126 | 54 | kwoo | } |
127 | 241 | bcoltin | |
128 | /** @} **/
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129 | 54 | kwoo | |
130 | 70 | kwoo | /**
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131 | * @brief Interrupt to handle I2C interrupts from the I2C hardware.
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132 | *
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133 | * Uses the status codes from the I2C register to handle the events
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134 | * needed to advance in I2C stages. For instance, you will get a bit for
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135 | * receiving a start ack, then a address ack, then a data ack, etc.
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136 | 78 | kwoo | * The events are handled in each switch case. The status codes are defined
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137 | * by avr-gcc in /util/twi.h but are the same codes as the Atmel documentation.
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138 | *
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139 | 70 | kwoo | * Bytes are sent by popping off the ring buffer. It also will keep track
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140 | * of what modes the send is in.
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141 | 78 | kwoo | *
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142 | 70 | kwoo | * Errors are handled here as well.
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143 | **/
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144 | 54 | kwoo | ISR(TWI_vect) { |
145 | 78 | kwoo | static char data_to_send; |
146 | static char addr_to_send = -1; |
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147 | char addr, statusCode;
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148 | 54 | kwoo | |
149 | 78 | kwoo | //Get status code (only upper 5 bits)
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150 | statusCode = (TWSR & 0xF8);
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151 | 54 | kwoo | |
152 | 78 | kwoo | switch (statusCode) {
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153 | //Start sent successfully
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154 | case TW_START:
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155 | case TW_REP_START:
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156 | /* Send address and write
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157 | * ring_buffer will not be empty */
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158 | RING_BUFFER_REMOVE(i2c_addr_buff, addr_to_send); |
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159 | RING_BUFFER_REMOVE(i2c_write_buff, data_to_send); |
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160 | |||
161 | /* first send the address */
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162 | TWDR = addr_to_send; |
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163 | |||
164 | //Turn off start bits
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165 | TWCR &= ~_BV(TWSTA); |
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166 | break;
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167 | |||
168 | //Master Transmit - Address sent succesfully
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169 | case TW_MT_SLA_ACK:
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170 | //Send byte
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171 | TWDR = data_to_send; |
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172 | PORTG &= ~_BV(PG2); |
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173 | break;
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174 | |||
175 | //Master Transmit - Data sent succesfully
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176 | case TW_MT_DATA_ACK:
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177 | //If there is still data to send
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178 | if(!RING_BUFFER_EMPTY(i2c_write_buff)) {
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179 | RING_BUFFER_PEEK(i2c_addr_buff, addr); |
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180 | 54 | kwoo | |
181 | 78 | kwoo | //Still data for this address
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182 | if (addr == addr_to_send) {
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183 | RING_BUFFER_REMOVE(i2c_addr_buff, addr); |
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184 | RING_BUFFER_REMOVE(i2c_write_buff, TWDR); |
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185 | break;
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186 | //No more data for this address, data for another address -> resend start
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187 | } else {
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188 | TWCR |= _BV(TWSTA); |
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189 | break;
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190 | } |
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191 | } |
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192 | /* there are no bytes to send */
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193 | TWCR |= _BV(TWSTO); |
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194 | start_flag = 0;
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195 | break;
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196 | |||
197 | //Master Transmit - Slave sends a nack, transmit is done
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198 | case TW_MT_DATA_NACK:
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199 | PORTG |= _BV(PG2); |
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200 | TWCR |= _BV(TWSTO); |
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201 | start_flag = 0;
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202 | break;
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203 | |||
204 | //Master Receive - Address sent succesfully
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205 | case TW_MR_SLA_ACK:
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206 | PORTG |= _BV(PG2); |
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207 | break;
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208 | |||
209 | //Master Receive - Data received succesfully
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210 | case TW_MR_DATA_ACK:
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211 | if(master_recv_function) {
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212 | if(!master_recv_function(TWDR)) {
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213 | TWCR &= ~_BV(TWEA); |
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214 | } |
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215 | } |
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216 | break;
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217 | |||
218 | //Master Receive - Slave sends a nack, transmission is done
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219 | case TW_MR_DATA_NACK:
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220 | TWCR |= _BV(TWEA); |
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221 | 54 | kwoo | |
222 | 78 | kwoo | //If there is still data to send
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223 | if(!RING_BUFFER_EMPTY(i2c_write_buff)) {
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224 | TWCR |= _BV(TWSTA); |
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225 | break;
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226 | } |
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227 | 54 | kwoo | |
228 | 78 | kwoo | /* there are no bytes to send */
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229 | TWCR |= _BV(TWSTO); |
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230 | start_flag = 0;
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231 | break;
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232 | 54 | kwoo | |
233 | 78 | kwoo | //Slave Transmit - Address received
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234 | case TW_ST_SLA_ACK:
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235 | break;
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236 | 54 | kwoo | |
237 | 78 | kwoo | //Slave Transmit - Nack received, no data requsted
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238 | case TW_ST_DATA_NACK:
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239 | break;
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240 | |||
241 | //Slave Transmit - Data requested, ack received
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242 | case TW_ST_DATA_ACK:
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243 | if (slave_send_function) {
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244 | TWDR = slave_send_function(); |
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245 | } |
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246 | break;
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247 | |||
248 | //Slave Receive - Address received
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249 | case TW_SR_SLA_ACK:
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250 | break;
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251 | |||
252 | //Slave Receive - Data received, ack returned
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253 | case TW_SR_DATA_ACK:
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254 | if(slave_recv_function) {
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255 | slave_recv_function(TWDR); |
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256 | } |
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257 | |||
258 | break;
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259 | 54 | kwoo | |
260 | 78 | kwoo | //Stop sent
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261 | case TW_SR_STOP:
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262 | break;
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263 | |||
264 | //Problem on the bus, reset everything
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265 | default:
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266 | TWCR |= _BV(TWSTO); |
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267 | start_flag = 0;
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268 | RING_BUFFER_CLEAR(i2c_write_buff); |
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269 | RING_BUFFER_CLEAR(i2c_addr_buff); |
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270 | } |
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271 | 54 | kwoo | |
272 | /* Toggle TWINT so that it resets and executes the commands */
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273 | TWCR |= _BV(TWINT); |
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274 | } |