root / arduino-1.0 / libraries / Wire / Wire.cpp @ 58d82c77
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1 | 58d82c77 | Tom Mullins | /*
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2 | TwoWire.cpp - TWI/I2C library for Wiring & Arduino
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3 | Copyright (c) 2006 Nicholas Zambetti. All right reserved.
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4 | |||
5 | This library is free software; you can redistribute it and/or
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6 | modify it under the terms of the GNU Lesser General Public
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7 | License as published by the Free Software Foundation; either
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8 | version 2.1 of the License, or (at your option) any later version.
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9 | |||
10 | This library is distributed in the hope that it will be useful,
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11 | but WITHOUT ANY WARRANTY; without even the implied warranty of
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12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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13 | Lesser General Public License for more details.
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14 | |||
15 | You should have received a copy of the GNU Lesser General Public
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16 | License along with this library; if not, write to the Free Software
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17 | Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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18 | */
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19 | |||
20 | extern "C" { |
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21 | #include <stdlib.h> |
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22 | #include <string.h> |
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23 | #include <inttypes.h> |
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24 | #include "twi.h" |
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25 | } |
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26 | |||
27 | #include "Wire.h" |
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28 | |||
29 | // Initialize Class Variables //////////////////////////////////////////////////
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30 | |||
31 | uint8_t TwoWire::rxBuffer[BUFFER_LENGTH]; |
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32 | uint8_t TwoWire::rxBufferIndex = 0;
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33 | uint8_t TwoWire::rxBufferLength = 0;
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34 | |||
35 | uint8_t TwoWire::txAddress = 0;
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36 | uint8_t TwoWire::txBuffer[BUFFER_LENGTH]; |
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37 | uint8_t TwoWire::txBufferIndex = 0;
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38 | uint8_t TwoWire::txBufferLength = 0;
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39 | |||
40 | uint8_t TwoWire::transmitting = 0;
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41 | void (*TwoWire::user_onRequest)(void); |
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42 | void (*TwoWire::user_onReceive)(int); |
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43 | |||
44 | // Constructors ////////////////////////////////////////////////////////////////
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45 | |||
46 | TwoWire::TwoWire() |
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47 | { |
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48 | } |
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49 | |||
50 | // Public Methods //////////////////////////////////////////////////////////////
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51 | |||
52 | void TwoWire::begin(void) |
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53 | { |
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54 | rxBufferIndex = 0;
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55 | rxBufferLength = 0;
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56 | |||
57 | txBufferIndex = 0;
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58 | txBufferLength = 0;
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59 | |||
60 | twi_init(); |
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61 | } |
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62 | |||
63 | void TwoWire::begin(uint8_t address)
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64 | { |
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65 | twi_setAddress(address); |
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66 | twi_attachSlaveTxEvent(onRequestService); |
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67 | twi_attachSlaveRxEvent(onReceiveService); |
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68 | begin(); |
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69 | } |
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70 | |||
71 | void TwoWire::begin(int address) |
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72 | { |
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73 | begin((uint8_t)address); |
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74 | } |
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75 | |||
76 | uint8_t TwoWire::requestFrom(uint8_t address, uint8_t quantity) |
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77 | { |
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78 | // clamp to buffer length
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79 | if(quantity > BUFFER_LENGTH){
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80 | quantity = BUFFER_LENGTH; |
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81 | } |
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82 | // perform blocking read into buffer
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83 | uint8_t read = twi_readFrom(address, rxBuffer, quantity); |
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84 | // set rx buffer iterator vars
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85 | rxBufferIndex = 0;
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86 | rxBufferLength = read; |
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87 | |||
88 | return read;
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89 | } |
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90 | |||
91 | uint8_t TwoWire::requestFrom(int address, int quantity) |
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92 | { |
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93 | return requestFrom((uint8_t)address, (uint8_t)quantity);
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94 | } |
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95 | |||
96 | void TwoWire::beginTransmission(uint8_t address)
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97 | { |
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98 | // indicate that we are transmitting
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99 | transmitting = 1;
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100 | // set address of targeted slave
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101 | txAddress = address; |
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102 | // reset tx buffer iterator vars
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103 | txBufferIndex = 0;
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104 | txBufferLength = 0;
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105 | } |
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106 | |||
107 | void TwoWire::beginTransmission(int address) |
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108 | { |
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109 | beginTransmission((uint8_t)address); |
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110 | } |
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111 | |||
112 | uint8_t TwoWire::endTransmission(void)
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113 | { |
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114 | // transmit buffer (blocking)
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115 | int8_t ret = twi_writeTo(txAddress, txBuffer, txBufferLength, 1);
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116 | // reset tx buffer iterator vars
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117 | txBufferIndex = 0;
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118 | txBufferLength = 0;
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119 | // indicate that we are done transmitting
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120 | transmitting = 0;
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121 | return ret;
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122 | } |
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123 | |||
124 | // must be called in:
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125 | // slave tx event callback
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126 | // or after beginTransmission(address)
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127 | size_t TwoWire::write(uint8_t data) |
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128 | { |
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129 | if(transmitting){
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130 | // in master transmitter mode
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131 | // don't bother if buffer is full
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132 | if(txBufferLength >= BUFFER_LENGTH){
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133 | setWriteError(); |
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134 | return 0; |
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135 | } |
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136 | // put byte in tx buffer
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137 | txBuffer[txBufferIndex] = data; |
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138 | ++txBufferIndex; |
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139 | // update amount in buffer
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140 | txBufferLength = txBufferIndex; |
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141 | }else{
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142 | // in slave send mode
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143 | // reply to master
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144 | twi_transmit(&data, 1);
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145 | } |
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146 | return 1; |
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147 | } |
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148 | |||
149 | // must be called in:
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150 | // slave tx event callback
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151 | // or after beginTransmission(address)
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152 | size_t TwoWire::write(const uint8_t *data, size_t quantity)
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153 | { |
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154 | if(transmitting){
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155 | // in master transmitter mode
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156 | for(size_t i = 0; i < quantity; ++i){ |
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157 | write(data[i]); |
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158 | } |
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159 | }else{
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160 | // in slave send mode
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161 | // reply to master
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162 | twi_transmit(data, quantity); |
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163 | } |
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164 | return quantity;
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165 | } |
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166 | |||
167 | // must be called in:
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168 | // slave rx event callback
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169 | // or after requestFrom(address, numBytes)
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170 | int TwoWire::available(void) |
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171 | { |
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172 | return rxBufferLength - rxBufferIndex;
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173 | } |
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174 | |||
175 | // must be called in:
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176 | // slave rx event callback
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177 | // or after requestFrom(address, numBytes)
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178 | int TwoWire::read(void) |
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179 | { |
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180 | int value = -1; |
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181 | |||
182 | // get each successive byte on each call
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183 | if(rxBufferIndex < rxBufferLength){
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184 | value = rxBuffer[rxBufferIndex]; |
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185 | ++rxBufferIndex; |
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186 | } |
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187 | |||
188 | return value;
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189 | } |
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190 | |||
191 | // must be called in:
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192 | // slave rx event callback
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193 | // or after requestFrom(address, numBytes)
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194 | int TwoWire::peek(void) |
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195 | { |
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196 | int value = -1; |
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197 | |||
198 | if(rxBufferIndex < rxBufferLength){
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199 | value = rxBuffer[rxBufferIndex]; |
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200 | } |
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201 | |||
202 | return value;
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203 | } |
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204 | |||
205 | void TwoWire::flush(void) |
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206 | { |
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207 | // XXX: to be implemented.
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208 | } |
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209 | |||
210 | // behind the scenes function that is called when data is received
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211 | void TwoWire::onReceiveService(uint8_t* inBytes, int numBytes) |
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212 | { |
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213 | // don't bother if user hasn't registered a callback
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214 | if(!user_onReceive){
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215 | return;
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216 | } |
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217 | // don't bother if rx buffer is in use by a master requestFrom() op
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218 | // i know this drops data, but it allows for slight stupidity
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219 | // meaning, they may not have read all the master requestFrom() data yet
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220 | if(rxBufferIndex < rxBufferLength){
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221 | return;
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222 | } |
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223 | // copy twi rx buffer into local read buffer
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224 | // this enables new reads to happen in parallel
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225 | for(uint8_t i = 0; i < numBytes; ++i){ |
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226 | rxBuffer[i] = inBytes[i]; |
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227 | } |
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228 | // set rx iterator vars
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229 | rxBufferIndex = 0;
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230 | rxBufferLength = numBytes; |
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231 | // alert user program
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232 | user_onReceive(numBytes); |
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233 | } |
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234 | |||
235 | // behind the scenes function that is called when data is requested
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236 | void TwoWire::onRequestService(void) |
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237 | { |
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238 | // don't bother if user hasn't registered a callback
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239 | if(!user_onRequest){
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240 | return;
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241 | } |
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242 | // reset tx buffer iterator vars
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243 | // !!! this will kill any pending pre-master sendTo() activity
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244 | txBufferIndex = 0;
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245 | txBufferLength = 0;
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246 | // alert user program
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247 | user_onRequest(); |
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248 | } |
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249 | |||
250 | // sets function called on slave write
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251 | void TwoWire::onReceive( void (*function)(int) ) |
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252 | { |
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253 | user_onReceive = function; |
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254 | } |
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255 | |||
256 | // sets function called on slave read
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257 | void TwoWire::onRequest( void (*function)(void) ) |
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258 | { |
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259 | user_onRequest = function; |
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260 | } |
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261 | |||
262 | // Preinstantiate Objects //////////////////////////////////////////////////////
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263 | |||
264 | TwoWire Wire = TwoWire(); |