Filipe Morais / Mbed 2 deprecated mini_project

Sensor with Web Server

Dependencies:   EthernetInterface mbed-rpc mbed-rtos mbed

OneWireCRC.cpp@0:c385e589a779, 2014-04-08 (annotated)

Committer:
afilipem
Date:
Tue Apr 08 12:13:32 2014 +0000
Revision:
0:c385e589a779
1 version;

Who changed what in which revision?

UserRevisionLine numberNew contents of line
afilipem 0:c385e589a779 1 /*
afilipem 0:c385e589a779 2 * OneWireCRC. This is a port to mbed of Jim Studt's Adruino One Wire
afilipem 0:c385e589a779 3 * library. Please see additional copyrights below this one, including
afilipem 0:c385e589a779 4 * references to other copyrights.
afilipem 0:c385e589a779 5 *
afilipem 0:c385e589a779 6 * Copyright (C) <2009> Petras Saduikis <petras@petras.co.uk>
afilipem 0:c385e589a779 7 *
afilipem 0:c385e589a779 8 * This file is part of OneWireCRC.
afilipem 0:c385e589a779 9 *
afilipem 0:c385e589a779 10 * OneWireCRC is free software: you can redistribute it and/or modify
afilipem 0:c385e589a779 11 * it under the terms of the GNU General Public License as published by
afilipem 0:c385e589a779 12 * the Free Software Foundation, either version 3 of the License, or
afilipem 0:c385e589a779 13 * (at your option) any later version.
afilipem 0:c385e589a779 14 *
afilipem 0:c385e589a779 15 * OneWireCRC is distributed in the hope that it will be useful,
afilipem 0:c385e589a779 16 * but WITHOUT ANY WARRANTY; without even the implied warranty of
afilipem 0:c385e589a779 17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
afilipem 0:c385e589a779 18 * GNU General Public License for more details.
afilipem 0:c385e589a779 19 *
afilipem 0:c385e589a779 20 * You should have received a copy of the GNU General Public License
afilipem 0:c385e589a779 21 * along with OneWireCRC. If not, see <http://www.gnu.org/licenses/>.
afilipem 0:c385e589a779 22 */
afilipem 0:c385e589a779 23 /*
afilipem 0:c385e589a779 24 Copyright (c) 2007, Jim Studt
afilipem 0:c385e589a779 25
afilipem 0:c385e589a779 26 Updated to work with arduino-0008 and to include skip() as of
afilipem 0:c385e589a779 27 2007/07/06. --RJL20
afilipem 0:c385e589a779 28
afilipem 0:c385e589a779 29 Modified to calculate the 8-bit CRC directly, avoiding the need for
afilipem 0:c385e589a779 30 the 256-byte lookup table to be loaded in RAM. Tested in arduino-0010
afilipem 0:c385e589a779 31 -- Tom Pollard, Jan 23, 2008
afilipem 0:c385e589a779 32
afilipem 0:c385e589a779 33 Permission is hereby granted, free of charge, to any person obtaining
afilipem 0:c385e589a779 34 a copy of this software and associated documentation files (the
afilipem 0:c385e589a779 35 "Software"), to deal in the Software without restriction, including
afilipem 0:c385e589a779 36 without limitation the rights to use, copy, modify, merge, publish,
afilipem 0:c385e589a779 37 distribute, sublicense, and/or sell copies of the Software, and to
afilipem 0:c385e589a779 38 permit persons to whom the Software is furnished to do so, subject to
afilipem 0:c385e589a779 39 the following conditions:
afilipem 0:c385e589a779 40
afilipem 0:c385e589a779 41 The above copyright notice and this permission notice shall be
afilipem 0:c385e589a779 42 included in all copies or substantial portions of the Software.
afilipem 0:c385e589a779 43
afilipem 0:c385e589a779 44 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
afilipem 0:c385e589a779 45 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
afilipem 0:c385e589a779 46 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
afilipem 0:c385e589a779 47 NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
afilipem 0:c385e589a779 48 LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
afilipem 0:c385e589a779 49 OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
afilipem 0:c385e589a779 50 WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
afilipem 0:c385e589a779 51
afilipem 0:c385e589a779 52 Much of the code was inspired by Derek Yerger's code, though I don't
afilipem 0:c385e589a779 53 think much of that remains. In any event that was..
afilipem 0:c385e589a779 54 (copyleft) 2006 by Derek Yerger - Free to distribute freely.
afilipem 0:c385e589a779 55
afilipem 0:c385e589a779 56 The CRC code was excerpted and inspired by the Dallas Semiconductor
afilipem 0:c385e589a779 57 sample code bearing this copyright.
afilipem 0:c385e589a779 58 //---------------------------------------------------------------------------
afilipem 0:c385e589a779 59 // Copyright (C) 2000 Dallas Semiconductor Corporation, All Rights Reserved.
afilipem 0:c385e589a779 60 //
afilipem 0:c385e589a779 61 // Permission is hereby granted, free of charge, to any person obtaining a
afilipem 0:c385e589a779 62 // copy of this software and associated documentation files (the "Software"),
afilipem 0:c385e589a779 63 // to deal in the Software without restriction, including without limitation
afilipem 0:c385e589a779 64 // the rights to use, copy, modify, merge, publish, distribute, sublicense,
afilipem 0:c385e589a779 65 // and/or sell copies of the Software, and to permit persons to whom the
afilipem 0:c385e589a779 66 // Software is furnished to do so, subject to the following conditions:
afilipem 0:c385e589a779 67 //
afilipem 0:c385e589a779 68 // The above copyright notice and this permission notice shall be included
afilipem 0:c385e589a779 69 // in all copies or substantial portions of the Software.
afilipem 0:c385e589a779 70 //
afilipem 0:c385e589a779 71 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
afilipem 0:c385e589a779 72 // OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
afilipem 0:c385e589a779 73 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
afilipem 0:c385e589a779 74 // IN NO EVENT SHALL DALLAS SEMICONDUCTOR BE LIABLE FOR ANY CLAIM, DAMAGES
afilipem 0:c385e589a779 75 // OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
afilipem 0:c385e589a779 76 // ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
afilipem 0:c385e589a779 77 // OTHER DEALINGS IN THE SOFTWARE.
afilipem 0:c385e589a779 78 //
afilipem 0:c385e589a779 79 // Except as contained in this notice, the name of Dallas Semiconductor
afilipem 0:c385e589a779 80 // shall not be used except as stated in the Dallas Semiconductor
afilipem 0:c385e589a779 81 // Branding Policy.
afilipem 0:c385e589a779 82 //--------------------------------------------------------------------------
afilipem 0:c385e589a779 83 */
afilipem 0:c385e589a779 84
afilipem 0:c385e589a779 85 #include "OneWireCRC.h"
afilipem 0:c385e589a779 86 #include "OneWireDefs.h"
afilipem 0:c385e589a779 87
afilipem 0:c385e589a779 88 // recommended data sheet timings in micro seconds
afilipem 0:c385e589a779 89 const int standardT[] = {6, 64, 60, 10, 9, 55, 0, 480, 70, 410};
afilipem 0:c385e589a779 90 const int overdriveT[] = {1.5, 7.5, 7.5, 2.5, 0.75, 7, 2.5, 70, 8.5, 40};
afilipem 0:c385e589a779 91
afilipem 0:c385e589a779 92 OneWireCRC::OneWireCRC(PinName oneWire, eSpeed speed) : oneWirePort(oneWire)
afilipem 0:c385e589a779 93 {
afilipem 0:c385e589a779 94 if (STANDARD == speed) timing = standardT;
afilipem 0:c385e589a779 95 else timing = overdriveT; // overdrive
afilipem 0:c385e589a779 96
afilipem 0:c385e589a779 97 resetSearch(); // reset address search state
afilipem 0:c385e589a779 98 }
afilipem 0:c385e589a779 99
afilipem 0:c385e589a779 100 // Generate a 1-wire reset, return 1 if no presence detect was found,
afilipem 0:c385e589a779 101 // return 0 otherwise.
afilipem 0:c385e589a779 102 // (NOTE: does not handle alarm presence from DS2404/DS1994)
afilipem 0:c385e589a779 103 int OneWireCRC::reset()
afilipem 0:c385e589a779 104 {
afilipem 0:c385e589a779 105
afilipem 0:c385e589a779 106 BYTE result = 0; // sample presence pulse result
afilipem 0:c385e589a779 107
afilipem 0:c385e589a779 108 wait_us(timing[6]);
afilipem 0:c385e589a779 109 oneWirePort.output();
afilipem 0:c385e589a779 110 oneWirePort = 0;
afilipem 0:c385e589a779 111 wait_us(timing[7]);
afilipem 0:c385e589a779 112 oneWirePort.input();
afilipem 0:c385e589a779 113 wait_us(timing[8]);
afilipem 0:c385e589a779 114 result = !(oneWirePort & 0x01);
afilipem 0:c385e589a779 115 wait_us(timing[9]);
afilipem 0:c385e589a779 116
afilipem 0:c385e589a779 117 return result;
afilipem 0:c385e589a779 118 }
afilipem 0:c385e589a779 119
afilipem 0:c385e589a779 120 //
afilipem 0:c385e589a779 121 // Write a bit. Port and bit is used to cut lookup time and provide
afilipem 0:c385e589a779 122 // more certain timing.
afilipem 0:c385e589a779 123 //
afilipem 0:c385e589a779 124 void OneWireCRC::writeBit(int bit)
afilipem 0:c385e589a779 125 {
afilipem 0:c385e589a779 126 bit = bit & 0x01;
afilipem 0:c385e589a779 127
afilipem 0:c385e589a779 128 if (bit)
afilipem 0:c385e589a779 129 {
afilipem 0:c385e589a779 130 // Write '1' bit
afilipem 0:c385e589a779 131 oneWirePort.output();
afilipem 0:c385e589a779 132 oneWirePort = 0;
afilipem 0:c385e589a779 133 wait_us(timing[0]);
afilipem 0:c385e589a779 134 oneWirePort.input();
afilipem 0:c385e589a779 135 wait_us(timing[1]);
afilipem 0:c385e589a779 136 }
afilipem 0:c385e589a779 137 else
afilipem 0:c385e589a779 138 {
afilipem 0:c385e589a779 139 // Write '0' bit
afilipem 0:c385e589a779 140 oneWirePort.output();
afilipem 0:c385e589a779 141 oneWirePort = 0;
afilipem 0:c385e589a779 142 wait_us(timing[2]);
afilipem 0:c385e589a779 143 oneWirePort.input();
afilipem 0:c385e589a779 144 wait_us(timing[3]);
afilipem 0:c385e589a779 145 }
afilipem 0:c385e589a779 146 }
afilipem 0:c385e589a779 147
afilipem 0:c385e589a779 148 //
afilipem 0:c385e589a779 149 // Read a bit. Port and bit is used to cut lookup time and provide
afilipem 0:c385e589a779 150 // more certain timing.
afilipem 0:c385e589a779 151 //
afilipem 0:c385e589a779 152 int OneWireCRC::readBit()
afilipem 0:c385e589a779 153 {
afilipem 0:c385e589a779 154 BYTE result;
afilipem 0:c385e589a779 155
afilipem 0:c385e589a779 156 oneWirePort.output();
afilipem 0:c385e589a779 157 oneWirePort = 0;
afilipem 0:c385e589a779 158 wait_us(timing[0]);
afilipem 0:c385e589a779 159 oneWirePort.input();
afilipem 0:c385e589a779 160 wait_us(timing[4]);
afilipem 0:c385e589a779 161 result = oneWirePort & 0x01;
afilipem 0:c385e589a779 162 wait_us(timing[5]);
afilipem 0:c385e589a779 163
afilipem 0:c385e589a779 164 return result;
afilipem 0:c385e589a779 165 }
afilipem 0:c385e589a779 166
afilipem 0:c385e589a779 167 //
afilipem 0:c385e589a779 168 // Write a byte. The writing code uses the active drivers to raise the
afilipem 0:c385e589a779 169 // pin high, if you need power after the write (e.g. DS18S20 in
afilipem 0:c385e589a779 170 // parasite power mode) then set 'power' to 1, otherwise the pin will
afilipem 0:c385e589a779 171 // go tri-state at the end of the write to avoid heating in a short or
afilipem 0:c385e589a779 172 // other mishap.
afilipem 0:c385e589a779 173 //
afilipem 0:c385e589a779 174 void OneWireCRC::writeByte(int data)
afilipem 0:c385e589a779 175 {
afilipem 0:c385e589a779 176 // Loop to write each bit in the byte, LS-bit first
afilipem 0:c385e589a779 177 for (int loop = 0; loop < 8; loop++)
afilipem 0:c385e589a779 178 {
afilipem 0:c385e589a779 179 writeBit(data & 0x01);
afilipem 0:c385e589a779 180
afilipem 0:c385e589a779 181 // shift the data byte for the next bit
afilipem 0:c385e589a779 182 data >>= 1;
afilipem 0:c385e589a779 183 }
afilipem 0:c385e589a779 184 }
afilipem 0:c385e589a779 185
afilipem 0:c385e589a779 186 //
afilipem 0:c385e589a779 187 // Read a byte
afilipem 0:c385e589a779 188 //
afilipem 0:c385e589a779 189 int OneWireCRC::readByte()
afilipem 0:c385e589a779 190 {
afilipem 0:c385e589a779 191 int result = 0;
afilipem 0:c385e589a779 192
afilipem 0:c385e589a779 193 for (int loop = 0; loop < 8; loop++)
afilipem 0:c385e589a779 194 {
afilipem 0:c385e589a779 195 // shift the result to get it ready for the next bit
afilipem 0:c385e589a779 196 result >>= 1;
afilipem 0:c385e589a779 197
afilipem 0:c385e589a779 198 // if result is one, then set MS bit
afilipem 0:c385e589a779 199 if (readBit()) result |= 0x80;
afilipem 0:c385e589a779 200 }
afilipem 0:c385e589a779 201
afilipem 0:c385e589a779 202 return result;
afilipem 0:c385e589a779 203 }
afilipem 0:c385e589a779 204
afilipem 0:c385e589a779 205 int OneWireCRC::touchByte(int data)
afilipem 0:c385e589a779 206 {
afilipem 0:c385e589a779 207 int result = 0;
afilipem 0:c385e589a779 208
afilipem 0:c385e589a779 209 for (int loop = 0; loop < 8; loop++)
afilipem 0:c385e589a779 210 {
afilipem 0:c385e589a779 211 // shift the result to get it ready for the next bit
afilipem 0:c385e589a779 212 result >>= 1;
afilipem 0:c385e589a779 213
afilipem 0:c385e589a779 214 // If sending a '1' then read a bit else write a '0'
afilipem 0:c385e589a779 215 if (data & 0x01)
afilipem 0:c385e589a779 216 {
afilipem 0:c385e589a779 217 if (readBit()) result |= 0x80;
afilipem 0:c385e589a779 218 }
afilipem 0:c385e589a779 219 else writeBit(0);
afilipem 0:c385e589a779 220
afilipem 0:c385e589a779 221 // shift the data byte for the next bit
afilipem 0:c385e589a779 222 data >>= 1;
afilipem 0:c385e589a779 223 }
afilipem 0:c385e589a779 224
afilipem 0:c385e589a779 225 return result;
afilipem 0:c385e589a779 226 }
afilipem 0:c385e589a779 227
afilipem 0:c385e589a779 228 void OneWireCRC::block(BYTE* data, int data_len)
afilipem 0:c385e589a779 229 {
afilipem 0:c385e589a779 230 for (int loop = 0; loop < data_len; loop++)
afilipem 0:c385e589a779 231 {
afilipem 0:c385e589a779 232 data[loop] = touchByte(data[loop]);
afilipem 0:c385e589a779 233 }
afilipem 0:c385e589a779 234 }
afilipem 0:c385e589a779 235
afilipem 0:c385e589a779 236 int OneWireCRC::overdriveSkip(BYTE* data, int data_len)
afilipem 0:c385e589a779 237 {
afilipem 0:c385e589a779 238 // set the speed to 'standard'
afilipem 0:c385e589a779 239 timing = standardT;
afilipem 0:c385e589a779 240
afilipem 0:c385e589a779 241 // reset all devices
afilipem 0:c385e589a779 242 if (reset()) return 0; // if no devices found
afilipem 0:c385e589a779 243
afilipem 0:c385e589a779 244 // overdrive skip command
afilipem 0:c385e589a779 245 writeByte(OVERDRIVE_SKIP);
afilipem 0:c385e589a779 246
afilipem 0:c385e589a779 247 // set the speed to 'overdrive'
afilipem 0:c385e589a779 248 timing = overdriveT;
afilipem 0:c385e589a779 249
afilipem 0:c385e589a779 250 // do a 1-Wire reset in 'overdrive' and return presence result
afilipem 0:c385e589a779 251 return reset();
afilipem 0:c385e589a779 252 }
afilipem 0:c385e589a779 253
afilipem 0:c385e589a779 254 //
afilipem 0:c385e589a779 255 // Do a ROM select
afilipem 0:c385e589a779 256 //
afilipem 0:c385e589a779 257 void OneWireCRC::matchROM(BYTE rom[8])
afilipem 0:c385e589a779 258 {
afilipem 0:c385e589a779 259 writeByte(MATCH_ROM); // Choose ROM
afilipem 0:c385e589a779 260
afilipem 0:c385e589a779 261 for(int i = 0; i < 8; i++) writeByte(rom[i]);
afilipem 0:c385e589a779 262 }
afilipem 0:c385e589a779 263
afilipem 0:c385e589a779 264 //
afilipem 0:c385e589a779 265 // Do a ROM skip
afilipem 0:c385e589a779 266 //
afilipem 0:c385e589a779 267 void OneWireCRC::skipROM()
afilipem 0:c385e589a779 268 {
afilipem 0:c385e589a779 269 writeByte(SKIP_ROM); // Skip ROM
afilipem 0:c385e589a779 270 }
afilipem 0:c385e589a779 271
afilipem 0:c385e589a779 272 //
afilipem 0:c385e589a779 273 // You need to use this function to start a search again from the beginning.
afilipem 0:c385e589a779 274 // You do not need to do it for the first search, though you could.
afilipem 0:c385e589a779 275 //
afilipem 0:c385e589a779 276 void OneWireCRC::resetSearch()
afilipem 0:c385e589a779 277 {
afilipem 0:c385e589a779 278 searchJunction = -1;
afilipem 0:c385e589a779 279 searchExhausted = false;
afilipem 0:c385e589a779 280 for (int i = 0; i < 8; i++)
afilipem 0:c385e589a779 281 {
afilipem 0:c385e589a779 282 address[i] = 0;
afilipem 0:c385e589a779 283 }
afilipem 0:c385e589a779 284 }
afilipem 0:c385e589a779 285
afilipem 0:c385e589a779 286 //
afilipem 0:c385e589a779 287 // Perform a search. If this function returns a '1' then it has
afilipem 0:c385e589a779 288 // enumerated the next device and you may retrieve the ROM from the
afilipem 0:c385e589a779 289 // OneWire::address variable. If there are no devices, no further
afilipem 0:c385e589a779 290 // devices, or something horrible happens in the middle of the
afilipem 0:c385e589a779 291 // enumeration then a 0 is returned. If a new device is found then
afilipem 0:c385e589a779 292 // its address is copied to newAddr. Use OneWire::reset_search() to
afilipem 0:c385e589a779 293 // start over.
afilipem 0:c385e589a779 294 //
afilipem 0:c385e589a779 295 BYTE OneWireCRC::search(BYTE* newAddr)
afilipem 0:c385e589a779 296 {
afilipem 0:c385e589a779 297 BYTE i;
afilipem 0:c385e589a779 298 int lastJunction = -1;
afilipem 0:c385e589a779 299 BYTE done = 1;
afilipem 0:c385e589a779 300
afilipem 0:c385e589a779 301 if (searchExhausted) return 0;
afilipem 0:c385e589a779 302
afilipem 0:c385e589a779 303 if (!reset()) return 0;
afilipem 0:c385e589a779 304
afilipem 0:c385e589a779 305 writeByte(SEARCH_ROM);
afilipem 0:c385e589a779 306
afilipem 0:c385e589a779 307 for(i = 0; i < 64; i++)
afilipem 0:c385e589a779 308 {
afilipem 0:c385e589a779 309 BYTE a = readBit( );
afilipem 0:c385e589a779 310 BYTE nota = readBit( );
afilipem 0:c385e589a779 311 BYTE ibyte = i/8;
afilipem 0:c385e589a779 312 BYTE ibit = 1 << (i & 7);
afilipem 0:c385e589a779 313
afilipem 0:c385e589a779 314 // I don't think this should happen, this means nothing responded, but maybe if
afilipem 0:c385e589a779 315 // something vanishes during the search it will come up.
afilipem 0:c385e589a779 316 if (a && nota) return 0;
afilipem 0:c385e589a779 317
afilipem 0:c385e589a779 318 if (!a && !nota)
afilipem 0:c385e589a779 319 {
afilipem 0:c385e589a779 320 if (i == searchJunction)
afilipem 0:c385e589a779 321 {
afilipem 0:c385e589a779 322 // this is our time to decide differently, we went zero last time, go one.
afilipem 0:c385e589a779 323 a = 1;
afilipem 0:c385e589a779 324 searchJunction = lastJunction;
afilipem 0:c385e589a779 325 }
afilipem 0:c385e589a779 326 else if (i < searchJunction)
afilipem 0:c385e589a779 327 {
afilipem 0:c385e589a779 328 // take whatever we took last time, look in address
afilipem 0:c385e589a779 329 if (address[ibyte] & ibit) a = 1;
afilipem 0:c385e589a779 330 else
afilipem 0:c385e589a779 331 {
afilipem 0:c385e589a779 332 // Only 0s count as pending junctions, we've already exhasuted the 0 side of 1s
afilipem 0:c385e589a779 333 a = 0;
afilipem 0:c385e589a779 334 done = 0;
afilipem 0:c385e589a779 335 lastJunction = i;
afilipem 0:c385e589a779 336 }
afilipem 0:c385e589a779 337 }
afilipem 0:c385e589a779 338 else
afilipem 0:c385e589a779 339 {
afilipem 0:c385e589a779 340 // we are blazing new tree, take the 0
afilipem 0:c385e589a779 341 a = 0;
afilipem 0:c385e589a779 342 searchJunction = i;
afilipem 0:c385e589a779 343 done = 0;
afilipem 0:c385e589a779 344 }
afilipem 0:c385e589a779 345 lastJunction = i;
afilipem 0:c385e589a779 346 }
afilipem 0:c385e589a779 347
afilipem 0:c385e589a779 348 if (a) address[ibyte] |= ibit;
afilipem 0:c385e589a779 349 else address[ibyte] &= ~ibit;
afilipem 0:c385e589a779 350
afilipem 0:c385e589a779 351 writeBit(a);
afilipem 0:c385e589a779 352 }
afilipem 0:c385e589a779 353
afilipem 0:c385e589a779 354 if (done) searchExhausted = true;
afilipem 0:c385e589a779 355
afilipem 0:c385e589a779 356 for (i = 0; i < 8; i++) newAddr[i] = address[i];
afilipem 0:c385e589a779 357
afilipem 0:c385e589a779 358 return 1;
afilipem 0:c385e589a779 359 }
afilipem 0:c385e589a779 360
afilipem 0:c385e589a779 361 // The 1-Wire CRC scheme is described in Maxim Application Note 27:
afilipem 0:c385e589a779 362 // "Understanding and Using Cyclic Redundancy Checks with Maxim iButton Products"
afilipem 0:c385e589a779 363 //
afilipem 0:c385e589a779 364
afilipem 0:c385e589a779 365 #if ONEWIRE_CRC8_TABLE
afilipem 0:c385e589a779 366 // This table comes from Dallas sample code where it is freely reusable,
afilipem 0:c385e589a779 367 // though Copyright (C) 2000 Dallas Semiconductor Corporation
afilipem 0:c385e589a779 368 static BYTE dscrc_table[] =
afilipem 0:c385e589a779 369 {
afilipem 0:c385e589a779 370 0, 94,188,226, 97, 63,221,131,194,156,126, 32,163,253, 31, 65,
afilipem 0:c385e589a779 371 157,195, 33,127,252,162, 64, 30, 95, 1,227,189, 62, 96,130,220,
afilipem 0:c385e589a779 372 35,125,159,193, 66, 28,254,160,225,191, 93, 3,128,222, 60, 98,
afilipem 0:c385e589a779 373 190,224, 2, 92,223,129, 99, 61,124, 34,192,158, 29, 67,161,255,
afilipem 0:c385e589a779 374 70, 24,250,164, 39,121,155,197,132,218, 56,102,229,187, 89, 7,
afilipem 0:c385e589a779 375 219,133,103, 57,186,228, 6, 88, 25, 71,165,251,120, 38,196,154,
afilipem 0:c385e589a779 376 101, 59,217,135, 4, 90,184,230,167,249, 27, 69,198,152,122, 36,
afilipem 0:c385e589a779 377 248,166, 68, 26,153,199, 37,123, 58,100,134,216, 91, 5,231,185,
afilipem 0:c385e589a779 378 140,210, 48,110,237,179, 81, 15, 78, 16,242,172, 47,113,147,205,
afilipem 0:c385e589a779 379 17, 79,173,243,112, 46,204,146,211,141,111, 49,178,236, 14, 80,
afilipem 0:c385e589a779 380 175,241, 19, 77,206,144,114, 44,109, 51,209,143, 12, 82,176,238,
afilipem 0:c385e589a779 381 50,108,142,208, 83, 13,239,177,240,174, 76, 18,145,207, 45,115,
afilipem 0:c385e589a779 382 202,148,118, 40,171,245, 23, 73, 8, 86,180,234,105, 55,213,139,
afilipem 0:c385e589a779 383 87, 9,235,181, 54,104,138,212,149,203, 41,119,244,170, 72, 22,
afilipem 0:c385e589a779 384 233,183, 85, 11,136,214, 52,106, 43,117,151,201, 74, 20,246,168,
afilipem 0:c385e589a779 385 116, 42,200,150, 21, 75,169,247,182,232, 10, 84,215,137,107, 53};
afilipem 0:c385e589a779 386
afilipem 0:c385e589a779 387 //
afilipem 0:c385e589a779 388 // Compute a Dallas Semiconductor 8 bit CRC. These show up in the ROM
afilipem 0:c385e589a779 389 // and the registers. (note: this might better be done without the
afilipem 0:c385e589a779 390 // table, it would probably be smaller and certainly fast enough
afilipem 0:c385e589a779 391 // compared to all those delayMicrosecond() calls. But I got
afilipem 0:c385e589a779 392 // confused, so I use this table from the examples.)
afilipem 0:c385e589a779 393 //
afilipem 0:c385e589a779 394 BYTE OneWireCRC::crc8(BYTE* addr, BYTE len)
afilipem 0:c385e589a779 395 {
afilipem 0:c385e589a779 396 BYTE i;
afilipem 0:c385e589a779 397 BYTE crc = 0;
afilipem 0:c385e589a779 398
afilipem 0:c385e589a779 399 for (i = 0; i < len; i++)
afilipem 0:c385e589a779 400 {
afilipem 0:c385e589a779 401 crc = dscrc_table[crc ^ addr[i] ];
afilipem 0:c385e589a779 402 }
afilipem 0:c385e589a779 403
afilipem 0:c385e589a779 404 return crc;
afilipem 0:c385e589a779 405 }
afilipem 0:c385e589a779 406 #else
afilipem 0:c385e589a779 407 //
afilipem 0:c385e589a779 408 // Compute a Dallas Semiconductor 8 bit CRC directly.
afilipem 0:c385e589a779 409 //
afilipem 0:c385e589a779 410 BYTE OneWireCRC::crc8(BYTE* addr, BYTE len)
afilipem 0:c385e589a779 411 {
afilipem 0:c385e589a779 412 BYTE i, j;
afilipem 0:c385e589a779 413 BYTE crc = 0;
afilipem 0:c385e589a779 414
afilipem 0:c385e589a779 415 for (i = 0; i < len; i++)
afilipem 0:c385e589a779 416 {
afilipem 0:c385e589a779 417 BYTE inbyte = addr[i];
afilipem 0:c385e589a779 418 for (j = 0; j < 8; j++)
afilipem 0:c385e589a779 419 {
afilipem 0:c385e589a779 420 BYTE mix = (crc ^ inbyte) & 0x01;
afilipem 0:c385e589a779 421 crc >>= 1;
afilipem 0:c385e589a779 422 if (mix) crc ^= 0x8C;
afilipem 0:c385e589a779 423 inbyte >>= 1;
afilipem 0:c385e589a779 424 }
afilipem 0:c385e589a779 425 }
afilipem 0:c385e589a779 426
afilipem 0:c385e589a779 427 return crc;
afilipem 0:c385e589a779 428 }
afilipem 0:c385e589a779 429 #endif
afilipem 0:c385e589a779 430
afilipem 0:c385e589a779 431 static short oddparity[16] = { 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0 };
afilipem 0:c385e589a779 432
afilipem 0:c385e589a779 433 //
afilipem 0:c385e589a779 434 // Compute a Dallas Semiconductor 16 bit CRC. I have never seen one of
afilipem 0:c385e589a779 435 // these, but here it is.
afilipem 0:c385e589a779 436 //
afilipem 0:c385e589a779 437 unsigned short OneWireCRC::crc16(unsigned short* data, unsigned short len)
afilipem 0:c385e589a779 438 {
afilipem 0:c385e589a779 439 unsigned short i;
afilipem 0:c385e589a779 440 unsigned short crc = 0;
afilipem 0:c385e589a779 441
afilipem 0:c385e589a779 442 for ( i = 0; i < len; i++)
afilipem 0:c385e589a779 443 {
afilipem 0:c385e589a779 444 unsigned short cdata = data[len];
afilipem 0:c385e589a779 445
afilipem 0:c385e589a779 446 cdata = (cdata ^ (crc & 0xff)) & 0xff;
afilipem 0:c385e589a779 447 crc >>= 8;
afilipem 0:c385e589a779 448
afilipem 0:c385e589a779 449 if (oddparity[cdata & 0xf] ^ oddparity[cdata >> 4]) crc ^= 0xc001;
afilipem 0:c385e589a779 450
afilipem 0:c385e589a779 451 cdata <<= 6;
afilipem 0:c385e589a779 452 crc ^= cdata;
afilipem 0:c385e589a779 453 cdata <<= 1;
afilipem 0:c385e589a779 454 crc ^= cdata;
afilipem 0:c385e589a779 455 }
afilipem 0:c385e589a779 456
afilipem 0:c385e589a779 457 return crc;
afilipem 0:c385e589a779 458 }
afilipem 0:c385e589a779 459