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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 | /**
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47 | * @defgroup i2c I2C
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48 | *
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49 | * @brief Provides Inter-Interconnected-Communications (I2C)
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50 | *
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51 | * Initiates I2C functions on an ATMega128 which has a fully hardware Two Wire
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52 | * Interface (TWI) module. Any Atmel chip with this hardware should be able to
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53 | * use the software.
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54 | *
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55 | * This code will operate in a multi-master enviornment and can be either a
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56 | * slave or a master at any time (as long as they are not one or the other at
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57 | * the moment. You can queue up multiple transmission modes in the buffer up to
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58 | 78 | kwoo | * the buffer size. The buffer is implemented as a ring buffer.
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59 | 70 | kwoo | *
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60 | * It is implemented using callback functions. Whenever you want to send a packet
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61 | * you can call the built in send function (as a master) and it will send an array
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62 | 78 | kwoo | * of bytes. Master recieve and slave send/receive are all handled by the call back
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63 | 70 | kwoo | * functions. It is up to the end user to create functions that will handle the
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64 | * receiving of packets. Their functions will be called with every byte recieved
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65 | * so you must either buffer the inputs or handle each one separately.
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66 | *
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67 | * On errors we will simply flush the entire buffer.
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68 | *
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69 | * For information on how I2C operates, read the wikipedia article
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70 | * http://en.wikipedia.org/wiki/I2c
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71 | * for a good explanation of how it works.
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72 | * @{
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73 | */
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74 | |||
75 | /**
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76 | * @brief Set bit rate 12 = 100kbit/s (max speed setting is 10 for an
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77 | 54 | kwoo | * 8 MHz clock). It is a divider, so the lower the number the faster the speed.
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78 | */
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79 | #define I2C_BIT_RATE_DIVIDER 0x0C |
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80 | |||
81 | static int start_flag; |
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82 | |||
83 | static fun_mrecv_t master_recv_function;
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84 | static fun_srecv_t slave_recv_function;
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85 | static fun_send_t slave_send_function;
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86 | |||
87 | RING_BUFFER_NEW(i2c_buffer, 128, char, i2c_write_buff, i2c_addr_buff); |
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88 | |||
89 | 70 | kwoo | |
90 | /**
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91 | * @brief Initializes the i2c module.
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92 | *
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93 | * Initializes the I2C module to start listening on the i2c lines. If the callback functions
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94 | * are not set to null they will be called when that transmission mode is called. The address
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95 | * is your address that you will listen to when you are not the master.
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96 | *
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97 | * @param addr Your address on the I2C bus.
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98 | * @param master_recv The address of the function to call when you receive a byte when you are a
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99 | * master.
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100 | * @param slave_recv The address of the function to call when you are a slave you receive data
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101 | * from the master
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102 | * @param slave_send The address of the function to call when you are a slave and the master
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103 | * requests data from you.
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104 | 241 | bcoltin | *
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105 | * @return 0 for success, nonzero for failure
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106 | 70 | kwoo | **/
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107 | 54 | kwoo | int i2c_init(char addr, fun_mrecv_t master_recv, fun_srecv_t slave_recv, fun_send_t slave_send) { |
108 | 78 | kwoo | master_recv_function = master_recv; |
109 | slave_recv_function = slave_recv; |
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110 | slave_send_function = slave_send; |
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111 | 54 | kwoo | |
112 | 78 | kwoo | RING_BUFFER_CLEAR(i2c_write_buff); |
113 | RING_BUFFER_CLEAR(i2c_addr_buff); |
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114 | 54 | kwoo | |
115 | 78 | kwoo | /* enables twi interrupt, automatic ack sending, and all twi hardware */
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116 | TWCR = (_BV(TWEA) | _BV(TWEN) | _BV(TWIE)); |
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117 | 54 | kwoo | |
118 | 78 | kwoo | /* sets the bit rate of data transmission */
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119 | TWBR = I2C_BIT_RATE_DIVIDER; |
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120 | 54 | kwoo | |
121 | 78 | kwoo | /* sets the address (it is stored in the 7 most significant bits) and allows
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122 | * global messages to be accepted */
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123 | TWAR = (addr << 1) | 1; |
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124 | 54 | kwoo | |
125 | 78 | kwoo | return 0; |
126 | 54 | kwoo | } |
127 | |||
128 | 70 | kwoo | /**
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129 | * @brief Sends a byte array over I2C as a master
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130 | *
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131 | * Will perform a send over I2C to the destination from data for the ammount of
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132 | * bytes that bytes is.
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133 | *
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134 | * @param dest Destination address of the data on the I2C bus.
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135 | * @param data The pointer to the byte array of data
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136 | * @param bytes The amount of bytes long that the byte array is. This is how
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137 | * many bytes from the array that the function will send.
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138 | 241 | bcoltin | *
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139 | * @return zero for success, nonzero for failure
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140 | 70 | kwoo | **/
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141 | 54 | kwoo | int i2c_send(char dest, char *data, size_t bytes) { |
142 | 78 | kwoo | int i;
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143 | 54 | kwoo | |
144 | 78 | kwoo | /* adding data to be sent to ring buffers is not atomic,
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145 | * so disable interrupts */
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146 | cli(); |
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147 | for(i = 0; i < bytes; i++) { |
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148 | if(RING_BUFFER_FULL(i2c_write_buff)) {
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149 | sei(); |
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150 | return -1; |
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151 | } |
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152 | |||
153 | RING_BUFFER_ADD(i2c_write_buff, data[i]); |
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154 | RING_BUFFER_ADD(i2c_addr_buff, dest << 1);
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155 | 54 | kwoo | } |
156 | |||
157 | 78 | kwoo | /* re-enable the interrupts */
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158 | sei(); |
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159 | |||
160 | /* send the start bit, only if this device is not currently master */
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161 | if(!start_flag) {
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162 | start_flag = 1;
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163 | TWCR |= _BV(TWSTA); |
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164 | TWCR |= _BV(TWINT); |
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165 | } |
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166 | 54 | kwoo | |
167 | 78 | kwoo | return 0; |
168 | 54 | kwoo | } |
169 | |||
170 | 70 | kwoo | /**
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171 | * @brief Send a master request to the destination
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172 | *
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173 | * Sends a request of data from the target address and calls
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174 | * the callback function to handle data as it comes in. This function will
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175 | * not work if the slave has not informationt to send or has nothing implemented
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176 | * to send it.
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177 | *
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178 | * @param dest The destination that we want to receive information from.
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179 | 241 | bcoltin | *
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180 | * @return 0 for success, nonzero for failure
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181 | 70 | kwoo | **/
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182 | 54 | kwoo | int i2c_request(char dest) { |
183 | 78 | kwoo | if(RING_BUFFER_FULL(i2c_write_buff))
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184 | return -1; |
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185 | 54 | kwoo | |
186 | 78 | kwoo | RING_BUFFER_ADD(i2c_write_buff, 0);
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187 | RING_BUFFER_ADD(i2c_addr_buff, (dest << 1) | 1); |
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188 | 54 | kwoo | |
189 | 78 | kwoo | if(!start_flag) {
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190 | start_flag = 1;
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191 | TWCR |= _BV(TWSTA); |
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192 | TWCR |= _BV(TWINT); |
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193 | } |
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194 | 54 | kwoo | |
195 | 78 | kwoo | return 0; |
196 | 54 | kwoo | } |
197 | 241 | bcoltin | |
198 | /** @} **/
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199 | 54 | kwoo | |
200 | 70 | kwoo | /**
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201 | * @brief Interrupt to handle I2C interrupts from the I2C hardware.
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202 | *
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203 | * Uses the status codes from the I2C register to handle the events
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204 | * needed to advance in I2C stages. For instance, you will get a bit for
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205 | * receiving a start ack, then a address ack, then a data ack, etc.
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206 | 78 | kwoo | * The events are handled in each switch case. The status codes are defined
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207 | * by avr-gcc in /util/twi.h but are the same codes as the Atmel documentation.
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208 | *
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209 | 70 | kwoo | * Bytes are sent by popping off the ring buffer. It also will keep track
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210 | * of what modes the send is in.
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211 | 78 | kwoo | *
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212 | 70 | kwoo | * Errors are handled here as well.
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213 | **/
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214 | 54 | kwoo | ISR(TWI_vect) { |
215 | 78 | kwoo | static char data_to_send; |
216 | static char addr_to_send = -1; |
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217 | char addr, statusCode;
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218 | 54 | kwoo | |
219 | 78 | kwoo | //Get status code (only upper 5 bits)
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220 | statusCode = (TWSR & 0xF8);
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221 | 54 | kwoo | |
222 | 78 | kwoo | switch (statusCode) {
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223 | //Start sent successfully
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224 | case TW_START:
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225 | case TW_REP_START:
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226 | /* Send address and write
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227 | * ring_buffer will not be empty */
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228 | RING_BUFFER_REMOVE(i2c_addr_buff, addr_to_send); |
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229 | RING_BUFFER_REMOVE(i2c_write_buff, data_to_send); |
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230 | |||
231 | /* first send the address */
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232 | TWDR = addr_to_send; |
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233 | |||
234 | //Turn off start bits
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235 | TWCR &= ~_BV(TWSTA); |
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236 | break;
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237 | |||
238 | //Master Transmit - Address sent succesfully
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239 | case TW_MT_SLA_ACK:
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240 | //Send byte
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241 | TWDR = data_to_send; |
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242 | PORTG &= ~_BV(PG2); |
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243 | break;
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244 | |||
245 | //Master Transmit - Data sent succesfully
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246 | case TW_MT_DATA_ACK:
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247 | //If there is still data to send
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248 | if(!RING_BUFFER_EMPTY(i2c_write_buff)) {
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249 | RING_BUFFER_PEEK(i2c_addr_buff, addr); |
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250 | 54 | kwoo | |
251 | 78 | kwoo | //Still data for this address
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252 | if (addr == addr_to_send) {
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253 | RING_BUFFER_REMOVE(i2c_addr_buff, addr); |
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254 | RING_BUFFER_REMOVE(i2c_write_buff, TWDR); |
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255 | break;
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256 | //No more data for this address, data for another address -> resend start
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257 | } else {
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258 | TWCR |= _BV(TWSTA); |
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259 | break;
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260 | } |
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261 | } |
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262 | /* there are no bytes to send */
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263 | TWCR |= _BV(TWSTO); |
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264 | start_flag = 0;
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265 | break;
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266 | |||
267 | //Master Transmit - Slave sends a nack, transmit is done
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268 | case TW_MT_DATA_NACK:
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269 | PORTG |= _BV(PG2); |
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270 | TWCR |= _BV(TWSTO); |
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271 | start_flag = 0;
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272 | break;
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273 | |||
274 | //Master Receive - Address sent succesfully
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275 | case TW_MR_SLA_ACK:
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276 | PORTG |= _BV(PG2); |
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277 | break;
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278 | |||
279 | //Master Receive - Data received succesfully
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280 | case TW_MR_DATA_ACK:
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281 | if(master_recv_function) {
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282 | if(!master_recv_function(TWDR)) {
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283 | TWCR &= ~_BV(TWEA); |
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284 | } |
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285 | } |
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286 | break;
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287 | |||
288 | //Master Receive - Slave sends a nack, transmission is done
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289 | case TW_MR_DATA_NACK:
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290 | TWCR |= _BV(TWEA); |
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291 | 54 | kwoo | |
292 | 78 | kwoo | //If there is still data to send
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293 | if(!RING_BUFFER_EMPTY(i2c_write_buff)) {
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294 | TWCR |= _BV(TWSTA); |
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295 | break;
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296 | } |
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297 | 54 | kwoo | |
298 | 78 | kwoo | /* there are no bytes to send */
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299 | TWCR |= _BV(TWSTO); |
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300 | start_flag = 0;
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301 | break;
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302 | 54 | kwoo | |
303 | 78 | kwoo | //Slave Transmit - Address received
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304 | case TW_ST_SLA_ACK:
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305 | break;
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306 | 54 | kwoo | |
307 | 78 | kwoo | //Slave Transmit - Nack received, no data requsted
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308 | case TW_ST_DATA_NACK:
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309 | break;
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310 | |||
311 | //Slave Transmit - Data requested, ack received
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312 | case TW_ST_DATA_ACK:
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313 | if (slave_send_function) {
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314 | TWDR = slave_send_function(); |
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315 | } |
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316 | break;
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317 | |||
318 | //Slave Receive - Address received
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319 | case TW_SR_SLA_ACK:
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320 | break;
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321 | |||
322 | //Slave Receive - Data received, ack returned
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323 | case TW_SR_DATA_ACK:
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324 | if(slave_recv_function) {
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325 | slave_recv_function(TWDR); |
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326 | } |
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327 | |||
328 | break;
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329 | 54 | kwoo | |
330 | 78 | kwoo | //Stop sent
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331 | case TW_SR_STOP:
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332 | break;
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333 | |||
334 | //Problem on the bus, reset everything
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335 | default:
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336 | TWCR |= _BV(TWSTO); |
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337 | start_flag = 0;
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338 | RING_BUFFER_CLEAR(i2c_write_buff); |
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339 | RING_BUFFER_CLEAR(i2c_addr_buff); |
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340 | } |
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341 | 54 | kwoo | |
342 | /* Toggle TWINT so that it resets and executes the commands */
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343 | TWCR |= _BV(TWINT); |
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344 | } |