jack zen / OneWire

DS18B20

Dependents:   DS1820_HelloWorld

OneWireCRC.cpp@0:a47e8ec71a4e, 2017-09-06 (annotated)

Committer:
jack__zen
Date:
Wed Sep 06 05:35:15 2017 +0000
Revision:
0:a47e8ec71a4e
onewire

Who changed what in which revision?

UserRevisionLine numberNew contents of line
jack__zen 0:a47e8ec71a4e 1 /*
jack__zen 0:a47e8ec71a4e 2 * OneWireCRC. This is a port to mbed of Jim Studt's Adruino One Wire
jack__zen 0:a47e8ec71a4e 3 * library. Please see additional copyrights below this one, including
jack__zen 0:a47e8ec71a4e 4 * references to other copyrights.
jack__zen 0:a47e8ec71a4e 5 *
jack__zen 0:a47e8ec71a4e 6 * Copyright (C) <2009> Petras Saduikis <petras@petras.co.uk>
jack__zen 0:a47e8ec71a4e 7 *
jack__zen 0:a47e8ec71a4e 8 * This file is part of OneWireCRC.
jack__zen 0:a47e8ec71a4e 9 *
jack__zen 0:a47e8ec71a4e 10 * OneWireCRC is free software: you can redistribute it and/or modify
jack__zen 0:a47e8ec71a4e 11 * it under the terms of the GNU General Public License as published by
jack__zen 0:a47e8ec71a4e 12 * the Free Software Foundation, either version 3 of the License, or
jack__zen 0:a47e8ec71a4e 13 * (at your option) any later version.
jack__zen 0:a47e8ec71a4e 14 *
jack__zen 0:a47e8ec71a4e 15 * OneWireCRC is distributed in the hope that it will be useful,
jack__zen 0:a47e8ec71a4e 16 * but WITHOUT ANY WARRANTY; without even the implied warranty of
jack__zen 0:a47e8ec71a4e 17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
jack__zen 0:a47e8ec71a4e 18 * GNU General Public License for more details.
jack__zen 0:a47e8ec71a4e 19 *
jack__zen 0:a47e8ec71a4e 20 * You should have received a copy of the GNU General Public License
jack__zen 0:a47e8ec71a4e 21 * along with OneWireCRC. If not, see <http://www.gnu.org/licenses/>.
jack__zen 0:a47e8ec71a4e 22 */
jack__zen 0:a47e8ec71a4e 23 /*
jack__zen 0:a47e8ec71a4e 24 Copyright (c) 2007, Jim Studt
jack__zen 0:a47e8ec71a4e 25
jack__zen 0:a47e8ec71a4e 26 Updated to work with arduino-0008 and to include skip() as of
jack__zen 0:a47e8ec71a4e 27 2007/07/06. --RJL20
jack__zen 0:a47e8ec71a4e 28
jack__zen 0:a47e8ec71a4e 29 Modified to calculate the 8-bit CRC directly, avoiding the need for
jack__zen 0:a47e8ec71a4e 30 the 256-byte lookup table to be loaded in RAM. Tested in arduino-0010
jack__zen 0:a47e8ec71a4e 31 -- Tom Pollard, Jan 23, 2008
jack__zen 0:a47e8ec71a4e 32
jack__zen 0:a47e8ec71a4e 33 Permission is hereby granted, free of charge, to any person obtaining
jack__zen 0:a47e8ec71a4e 34 a copy of this software and associated documentation files (the
jack__zen 0:a47e8ec71a4e 35 "Software"), to deal in the Software without restriction, including
jack__zen 0:a47e8ec71a4e 36 without limitation the rights to use, copy, modify, merge, publish,
jack__zen 0:a47e8ec71a4e 37 distribute, sublicense, and/or sell copies of the Software, and to
jack__zen 0:a47e8ec71a4e 38 permit persons to whom the Software is furnished to do so, subject to
jack__zen 0:a47e8ec71a4e 39 the following conditions:
jack__zen 0:a47e8ec71a4e 40
jack__zen 0:a47e8ec71a4e 41 The above copyright notice and this permission notice shall be
jack__zen 0:a47e8ec71a4e 42 included in all copies or substantial portions of the Software.
jack__zen 0:a47e8ec71a4e 43
jack__zen 0:a47e8ec71a4e 44 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
jack__zen 0:a47e8ec71a4e 45 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
jack__zen 0:a47e8ec71a4e 46 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
jack__zen 0:a47e8ec71a4e 47 NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
jack__zen 0:a47e8ec71a4e 48 LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
jack__zen 0:a47e8ec71a4e 49 OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
jack__zen 0:a47e8ec71a4e 50 WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
jack__zen 0:a47e8ec71a4e 51
jack__zen 0:a47e8ec71a4e 52 Much of the code was inspired by Derek Yerger's code, though I don't
jack__zen 0:a47e8ec71a4e 53 think much of that remains. In any event that was..
jack__zen 0:a47e8ec71a4e 54 (copyleft) 2006 by Derek Yerger - Free to distribute freely.
jack__zen 0:a47e8ec71a4e 55
jack__zen 0:a47e8ec71a4e 56 The CRC code was excerpted and inspired by the Dallas Semiconductor
jack__zen 0:a47e8ec71a4e 57 sample code bearing this copyright.
jack__zen 0:a47e8ec71a4e 58 //---------------------------------------------------------------------------
jack__zen 0:a47e8ec71a4e 59 // Copyright (C) 2000 Dallas Semiconductor Corporation, All Rights Reserved.
jack__zen 0:a47e8ec71a4e 60 //
jack__zen 0:a47e8ec71a4e 61 // Permission is hereby granted, free of charge, to any person obtaining a
jack__zen 0:a47e8ec71a4e 62 // copy of this software and associated documentation files (the "Software"),
jack__zen 0:a47e8ec71a4e 63 // to deal in the Software without restriction, including without limitation
jack__zen 0:a47e8ec71a4e 64 // the rights to use, copy, modify, merge, publish, distribute, sublicense,
jack__zen 0:a47e8ec71a4e 65 // and/or sell copies of the Software, and to permit persons to whom the
jack__zen 0:a47e8ec71a4e 66 // Software is furnished to do so, subject to the following conditions:
jack__zen 0:a47e8ec71a4e 67 //
jack__zen 0:a47e8ec71a4e 68 // The above copyright notice and this permission notice shall be included
jack__zen 0:a47e8ec71a4e 69 // in all copies or substantial portions of the Software.
jack__zen 0:a47e8ec71a4e 70 //
jack__zen 0:a47e8ec71a4e 71 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
jack__zen 0:a47e8ec71a4e 72 // OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
jack__zen 0:a47e8ec71a4e 73 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
jack__zen 0:a47e8ec71a4e 74 // IN NO EVENT SHALL DALLAS SEMICONDUCTOR BE LIABLE FOR ANY CLAIM, DAMAGES
jack__zen 0:a47e8ec71a4e 75 // OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
jack__zen 0:a47e8ec71a4e 76 // ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
jack__zen 0:a47e8ec71a4e 77 // OTHER DEALINGS IN THE SOFTWARE.
jack__zen 0:a47e8ec71a4e 78 //
jack__zen 0:a47e8ec71a4e 79 // Except as contained in this notice, the name of Dallas Semiconductor
jack__zen 0:a47e8ec71a4e 80 // shall not be used except as stated in the Dallas Semiconductor
jack__zen 0:a47e8ec71a4e 81 // Branding Policy.
jack__zen 0:a47e8ec71a4e 82 //--------------------------------------------------------------------------
jack__zen 0:a47e8ec71a4e 83 */
jack__zen 0:a47e8ec71a4e 84
jack__zen 0:a47e8ec71a4e 85 #include "OneWireCRC.h"
jack__zen 0:a47e8ec71a4e 86 #include "OneWireDefs.h"
jack__zen 0:a47e8ec71a4e 87
jack__zen 0:a47e8ec71a4e 88 // recommended data sheet timings in micro seconds
jack__zen 0:a47e8ec71a4e 89 const int standardT[] = {6, 64, 60, 10, 9, 55, 0, 480, 70, 410};
jack__zen 0:a47e8ec71a4e 90 const int overdriveT[] = {1.5, 7.5, 7.5, 2.5, 0.75, 7, 2.5, 70, 8.5, 40};
jack__zen 0:a47e8ec71a4e 91
jack__zen 0:a47e8ec71a4e 92 OneWireCRC::OneWireCRC(PinName oneWire, eSpeed speed) : oneWirePort(oneWire)
jack__zen 0:a47e8ec71a4e 93 {
jack__zen 0:a47e8ec71a4e 94 if (STANDARD == speed) timing = standardT;
jack__zen 0:a47e8ec71a4e 95 else timing = overdriveT; // overdrive
jack__zen 0:a47e8ec71a4e 96
jack__zen 0:a47e8ec71a4e 97 resetSearch(); // reset address search state
jack__zen 0:a47e8ec71a4e 98 }
jack__zen 0:a47e8ec71a4e 99
jack__zen 0:a47e8ec71a4e 100 // Generate a 1-wire reset, return 1 if no presence detect was found,
jack__zen 0:a47e8ec71a4e 101 // return 0 otherwise.
jack__zen 0:a47e8ec71a4e 102 // (NOTE: does not handle alarm presence from DS2404/DS1994)
jack__zen 0:a47e8ec71a4e 103 int OneWireCRC::reset()
jack__zen 0:a47e8ec71a4e 104 {
jack__zen 0:a47e8ec71a4e 105
jack__zen 0:a47e8ec71a4e 106 BYTE result = 0; // sample presence pulse result
jack__zen 0:a47e8ec71a4e 107
jack__zen 0:a47e8ec71a4e 108 wait_us(timing[6]);
jack__zen 0:a47e8ec71a4e 109 oneWirePort.output();
jack__zen 0:a47e8ec71a4e 110 oneWirePort = 0;
jack__zen 0:a47e8ec71a4e 111 wait_us(timing[7]);
jack__zen 0:a47e8ec71a4e 112 oneWirePort.input();
jack__zen 0:a47e8ec71a4e 113 wait_us(timing[8]);
jack__zen 0:a47e8ec71a4e 114 result = !(oneWirePort & 0x01);
jack__zen 0:a47e8ec71a4e 115 wait_us(timing[9]);
jack__zen 0:a47e8ec71a4e 116
jack__zen 0:a47e8ec71a4e 117 return result;
jack__zen 0:a47e8ec71a4e 118 }
jack__zen 0:a47e8ec71a4e 119
jack__zen 0:a47e8ec71a4e 120 //
jack__zen 0:a47e8ec71a4e 121 // Write a bit. Port and bit is used to cut lookup time and provide
jack__zen 0:a47e8ec71a4e 122 // more certain timing.
jack__zen 0:a47e8ec71a4e 123 //
jack__zen 0:a47e8ec71a4e 124 void OneWireCRC::writeBit(int bit)
jack__zen 0:a47e8ec71a4e 125 {
jack__zen 0:a47e8ec71a4e 126 bit = bit & 0x01;
jack__zen 0:a47e8ec71a4e 127
jack__zen 0:a47e8ec71a4e 128 if (bit)
jack__zen 0:a47e8ec71a4e 129 {
jack__zen 0:a47e8ec71a4e 130 // Write '1' bit
jack__zen 0:a47e8ec71a4e 131 oneWirePort.output();
jack__zen 0:a47e8ec71a4e 132 oneWirePort = 0;
jack__zen 0:a47e8ec71a4e 133 wait_us(timing[0]);
jack__zen 0:a47e8ec71a4e 134 oneWirePort.input();
jack__zen 0:a47e8ec71a4e 135 wait_us(timing[1]);
jack__zen 0:a47e8ec71a4e 136 }
jack__zen 0:a47e8ec71a4e 137 else
jack__zen 0:a47e8ec71a4e 138 {
jack__zen 0:a47e8ec71a4e 139 // Write '0' bit
jack__zen 0:a47e8ec71a4e 140 oneWirePort.output();
jack__zen 0:a47e8ec71a4e 141 oneWirePort = 0;
jack__zen 0:a47e8ec71a4e 142 wait_us(timing[2]);
jack__zen 0:a47e8ec71a4e 143 oneWirePort.input();
jack__zen 0:a47e8ec71a4e 144 wait_us(timing[3]);
jack__zen 0:a47e8ec71a4e 145 }
jack__zen 0:a47e8ec71a4e 146 }
jack__zen 0:a47e8ec71a4e 147
jack__zen 0:a47e8ec71a4e 148 //
jack__zen 0:a47e8ec71a4e 149 // Read a bit. Port and bit is used to cut lookup time and provide
jack__zen 0:a47e8ec71a4e 150 // more certain timing.
jack__zen 0:a47e8ec71a4e 151 //
jack__zen 0:a47e8ec71a4e 152 int OneWireCRC::readBit()
jack__zen 0:a47e8ec71a4e 153 {
jack__zen 0:a47e8ec71a4e 154 BYTE result;
jack__zen 0:a47e8ec71a4e 155
jack__zen 0:a47e8ec71a4e 156 oneWirePort.output();
jack__zen 0:a47e8ec71a4e 157 oneWirePort = 0;
jack__zen 0:a47e8ec71a4e 158 wait_us(timing[0]);
jack__zen 0:a47e8ec71a4e 159 oneWirePort.input();
jack__zen 0:a47e8ec71a4e 160 wait_us(timing[4]);
jack__zen 0:a47e8ec71a4e 161 result = oneWirePort & 0x01;
jack__zen 0:a47e8ec71a4e 162 wait_us(timing[5]);
jack__zen 0:a47e8ec71a4e 163
jack__zen 0:a47e8ec71a4e 164 return result;
jack__zen 0:a47e8ec71a4e 165 }
jack__zen 0:a47e8ec71a4e 166
jack__zen 0:a47e8ec71a4e 167 //
jack__zen 0:a47e8ec71a4e 168 // Write a byte. The writing code uses the active drivers to raise the
jack__zen 0:a47e8ec71a4e 169 // pin high, if you need power after the write (e.g. DS18S20 in
jack__zen 0:a47e8ec71a4e 170 // parasite power mode) then set 'power' to 1, otherwise the pin will
jack__zen 0:a47e8ec71a4e 171 // go tri-state at the end of the write to avoid heating in a short or
jack__zen 0:a47e8ec71a4e 172 // other mishap.
jack__zen 0:a47e8ec71a4e 173 //
jack__zen 0:a47e8ec71a4e 174 void OneWireCRC::writeByte(int data)
jack__zen 0:a47e8ec71a4e 175 {
jack__zen 0:a47e8ec71a4e 176 // Loop to write each bit in the byte, LS-bit first
jack__zen 0:a47e8ec71a4e 177 for (int loop = 0; loop < 8; loop++)
jack__zen 0:a47e8ec71a4e 178 {
jack__zen 0:a47e8ec71a4e 179 writeBit(data & 0x01);
jack__zen 0:a47e8ec71a4e 180
jack__zen 0:a47e8ec71a4e 181 // shift the data byte for the next bit
jack__zen 0:a47e8ec71a4e 182 data >>= 1;
jack__zen 0:a47e8ec71a4e 183 }
jack__zen 0:a47e8ec71a4e 184 }
jack__zen 0:a47e8ec71a4e 185
jack__zen 0:a47e8ec71a4e 186 //
jack__zen 0:a47e8ec71a4e 187 // Read a byte
jack__zen 0:a47e8ec71a4e 188 //
jack__zen 0:a47e8ec71a4e 189 int OneWireCRC::readByte()
jack__zen 0:a47e8ec71a4e 190 {
jack__zen 0:a47e8ec71a4e 191 int result = 0;
jack__zen 0:a47e8ec71a4e 192
jack__zen 0:a47e8ec71a4e 193 for (int loop = 0; loop < 8; loop++)
jack__zen 0:a47e8ec71a4e 194 {
jack__zen 0:a47e8ec71a4e 195 // shift the result to get it ready for the next bit
jack__zen 0:a47e8ec71a4e 196 result >>= 1;
jack__zen 0:a47e8ec71a4e 197
jack__zen 0:a47e8ec71a4e 198 // if result is one, then set MS bit
jack__zen 0:a47e8ec71a4e 199 if (readBit()) result |= 0x80;
jack__zen 0:a47e8ec71a4e 200 }
jack__zen 0:a47e8ec71a4e 201
jack__zen 0:a47e8ec71a4e 202 return result;
jack__zen 0:a47e8ec71a4e 203 }
jack__zen 0:a47e8ec71a4e 204
jack__zen 0:a47e8ec71a4e 205 int OneWireCRC::touchByte(int data)
jack__zen 0:a47e8ec71a4e 206 {
jack__zen 0:a47e8ec71a4e 207 int result = 0;
jack__zen 0:a47e8ec71a4e 208
jack__zen 0:a47e8ec71a4e 209 for (int loop = 0; loop < 8; loop++)
jack__zen 0:a47e8ec71a4e 210 {
jack__zen 0:a47e8ec71a4e 211 // shift the result to get it ready for the next bit
jack__zen 0:a47e8ec71a4e 212 result >>= 1;
jack__zen 0:a47e8ec71a4e 213
jack__zen 0:a47e8ec71a4e 214 // If sending a '1' then read a bit else write a '0'
jack__zen 0:a47e8ec71a4e 215 if (data & 0x01)
jack__zen 0:a47e8ec71a4e 216 {
jack__zen 0:a47e8ec71a4e 217 if (readBit()) result |= 0x80;
jack__zen 0:a47e8ec71a4e 218 }
jack__zen 0:a47e8ec71a4e 219 else writeBit(0);
jack__zen 0:a47e8ec71a4e 220
jack__zen 0:a47e8ec71a4e 221 // shift the data byte for the next bit
jack__zen 0:a47e8ec71a4e 222 data >>= 1;
jack__zen 0:a47e8ec71a4e 223 }
jack__zen 0:a47e8ec71a4e 224
jack__zen 0:a47e8ec71a4e 225 return result;
jack__zen 0:a47e8ec71a4e 226 }
jack__zen 0:a47e8ec71a4e 227
jack__zen 0:a47e8ec71a4e 228 void OneWireCRC::block(BYTE* data, int data_len)
jack__zen 0:a47e8ec71a4e 229 {
jack__zen 0:a47e8ec71a4e 230 for (int loop = 0; loop < data_len; loop++)
jack__zen 0:a47e8ec71a4e 231 {
jack__zen 0:a47e8ec71a4e 232 data[loop] = touchByte(data[loop]);
jack__zen 0:a47e8ec71a4e 233 }
jack__zen 0:a47e8ec71a4e 234 }
jack__zen 0:a47e8ec71a4e 235
jack__zen 0:a47e8ec71a4e 236 int OneWireCRC::overdriveSkip(BYTE* data, int data_len)
jack__zen 0:a47e8ec71a4e 237 {
jack__zen 0:a47e8ec71a4e 238 // set the speed to 'standard'
jack__zen 0:a47e8ec71a4e 239 timing = standardT;
jack__zen 0:a47e8ec71a4e 240
jack__zen 0:a47e8ec71a4e 241 // reset all devices
jack__zen 0:a47e8ec71a4e 242 if (reset()) return 0; // if no devices found
jack__zen 0:a47e8ec71a4e 243
jack__zen 0:a47e8ec71a4e 244 // overdrive skip command
jack__zen 0:a47e8ec71a4e 245 writeByte(OVERDRIVE_SKIP);
jack__zen 0:a47e8ec71a4e 246
jack__zen 0:a47e8ec71a4e 247 // set the speed to 'overdrive'
jack__zen 0:a47e8ec71a4e 248 timing = overdriveT;
jack__zen 0:a47e8ec71a4e 249
jack__zen 0:a47e8ec71a4e 250 // do a 1-Wire reset in 'overdrive' and return presence result
jack__zen 0:a47e8ec71a4e 251 return reset();
jack__zen 0:a47e8ec71a4e 252 }
jack__zen 0:a47e8ec71a4e 253
jack__zen 0:a47e8ec71a4e 254 //
jack__zen 0:a47e8ec71a4e 255 // Do a ROM select
jack__zen 0:a47e8ec71a4e 256 //
jack__zen 0:a47e8ec71a4e 257 void OneWireCRC::matchROM(BYTE rom[8])
jack__zen 0:a47e8ec71a4e 258 {
jack__zen 0:a47e8ec71a4e 259 writeByte(MATCH_ROM); // Choose ROM
jack__zen 0:a47e8ec71a4e 260
jack__zen 0:a47e8ec71a4e 261 for(int i = 0; i < 8; i++) writeByte(rom[i]);
jack__zen 0:a47e8ec71a4e 262 }
jack__zen 0:a47e8ec71a4e 263
jack__zen 0:a47e8ec71a4e 264 //
jack__zen 0:a47e8ec71a4e 265 // Do a ROM skip
jack__zen 0:a47e8ec71a4e 266 //
jack__zen 0:a47e8ec71a4e 267 void OneWireCRC::skipROM()
jack__zen 0:a47e8ec71a4e 268 {
jack__zen 0:a47e8ec71a4e 269 writeByte(SKIP_ROM); // Skip ROM
jack__zen 0:a47e8ec71a4e 270 }
jack__zen 0:a47e8ec71a4e 271
jack__zen 0:a47e8ec71a4e 272 //
jack__zen 0:a47e8ec71a4e 273 // You need to use this function to start a search again from the beginning.
jack__zen 0:a47e8ec71a4e 274 // You do not need to do it for the first search, though you could.
jack__zen 0:a47e8ec71a4e 275 //
jack__zen 0:a47e8ec71a4e 276 void OneWireCRC::resetSearch()
jack__zen 0:a47e8ec71a4e 277 {
jack__zen 0:a47e8ec71a4e 278 searchJunction = -1;
jack__zen 0:a47e8ec71a4e 279 searchExhausted = false;
jack__zen 0:a47e8ec71a4e 280 for (int i = 0; i < 8; i++)
jack__zen 0:a47e8ec71a4e 281 {
jack__zen 0:a47e8ec71a4e 282 address[i] = 0;
jack__zen 0:a47e8ec71a4e 283 }
jack__zen 0:a47e8ec71a4e 284 }
jack__zen 0:a47e8ec71a4e 285
jack__zen 0:a47e8ec71a4e 286 //
jack__zen 0:a47e8ec71a4e 287 // Perform a search. If this function returns a '1' then it has
jack__zen 0:a47e8ec71a4e 288 // enumerated the next device and you may retrieve the ROM from the
jack__zen 0:a47e8ec71a4e 289 // OneWire::address variable. If there are no devices, no further
jack__zen 0:a47e8ec71a4e 290 // devices, or something horrible happens in the middle of the
jack__zen 0:a47e8ec71a4e 291 // enumeration then a 0 is returned. If a new device is found then
jack__zen 0:a47e8ec71a4e 292 // its address is copied to newAddr. Use OneWire::reset_search() to
jack__zen 0:a47e8ec71a4e 293 // start over.
jack__zen 0:a47e8ec71a4e 294 //
jack__zen 0:a47e8ec71a4e 295 BYTE OneWireCRC::search(BYTE* newAddr)
jack__zen 0:a47e8ec71a4e 296 {
jack__zen 0:a47e8ec71a4e 297 BYTE i;
jack__zen 0:a47e8ec71a4e 298 int lastJunction = -1;
jack__zen 0:a47e8ec71a4e 299 BYTE done = 1;
jack__zen 0:a47e8ec71a4e 300
jack__zen 0:a47e8ec71a4e 301 if (searchExhausted) return 0;
jack__zen 0:a47e8ec71a4e 302
jack__zen 0:a47e8ec71a4e 303 if (!reset()) return 0;
jack__zen 0:a47e8ec71a4e 304
jack__zen 0:a47e8ec71a4e 305 writeByte(SEARCH_ROM);
jack__zen 0:a47e8ec71a4e 306
jack__zen 0:a47e8ec71a4e 307 for(i = 0; i < 64; i++)
jack__zen 0:a47e8ec71a4e 308 {
jack__zen 0:a47e8ec71a4e 309 BYTE a = readBit( );
jack__zen 0:a47e8ec71a4e 310 BYTE nota = readBit( );
jack__zen 0:a47e8ec71a4e 311 BYTE ibyte = i/8;
jack__zen 0:a47e8ec71a4e 312 BYTE ibit = 1 << (i & 7);
jack__zen 0:a47e8ec71a4e 313
jack__zen 0:a47e8ec71a4e 314 // I don't think this should happen, this means nothing responded, but maybe if
jack__zen 0:a47e8ec71a4e 315 // something vanishes during the search it will come up.
jack__zen 0:a47e8ec71a4e 316 if (a && nota) return 0;
jack__zen 0:a47e8ec71a4e 317
jack__zen 0:a47e8ec71a4e 318 if (!a && !nota)
jack__zen 0:a47e8ec71a4e 319 {
jack__zen 0:a47e8ec71a4e 320 if (i == searchJunction)
jack__zen 0:a47e8ec71a4e 321 {
jack__zen 0:a47e8ec71a4e 322 // this is our time to decide differently, we went zero last time, go one.
jack__zen 0:a47e8ec71a4e 323 a = 1;
jack__zen 0:a47e8ec71a4e 324 searchJunction = lastJunction;
jack__zen 0:a47e8ec71a4e 325 }
jack__zen 0:a47e8ec71a4e 326 else if (i < searchJunction)
jack__zen 0:a47e8ec71a4e 327 {
jack__zen 0:a47e8ec71a4e 328 // take whatever we took last time, look in address
jack__zen 0:a47e8ec71a4e 329 if (address[ibyte] & ibit) a = 1;
jack__zen 0:a47e8ec71a4e 330 else
jack__zen 0:a47e8ec71a4e 331 {
jack__zen 0:a47e8ec71a4e 332 // Only 0s count as pending junctions, we've already exhasuted the 0 side of 1s
jack__zen 0:a47e8ec71a4e 333 a = 0;
jack__zen 0:a47e8ec71a4e 334 done = 0;
jack__zen 0:a47e8ec71a4e 335 lastJunction = i;
jack__zen 0:a47e8ec71a4e 336 }
jack__zen 0:a47e8ec71a4e 337 }
jack__zen 0:a47e8ec71a4e 338 else
jack__zen 0:a47e8ec71a4e 339 {
jack__zen 0:a47e8ec71a4e 340 // we are blazing new tree, take the 0
jack__zen 0:a47e8ec71a4e 341 a = 0;
jack__zen 0:a47e8ec71a4e 342 searchJunction = i;
jack__zen 0:a47e8ec71a4e 343 done = 0;
jack__zen 0:a47e8ec71a4e 344 }
jack__zen 0:a47e8ec71a4e 345 lastJunction = i;
jack__zen 0:a47e8ec71a4e 346 }
jack__zen 0:a47e8ec71a4e 347
jack__zen 0:a47e8ec71a4e 348 if (a) address[ibyte] |= ibit;
jack__zen 0:a47e8ec71a4e 349 else address[ibyte] &= ~ibit;
jack__zen 0:a47e8ec71a4e 350
jack__zen 0:a47e8ec71a4e 351 writeBit(a);
jack__zen 0:a47e8ec71a4e 352 }
jack__zen 0:a47e8ec71a4e 353
jack__zen 0:a47e8ec71a4e 354 if (done) searchExhausted = true;
jack__zen 0:a47e8ec71a4e 355
jack__zen 0:a47e8ec71a4e 356 for (i = 0; i < 8; i++) newAddr[i] = address[i];
jack__zen 0:a47e8ec71a4e 357
jack__zen 0:a47e8ec71a4e 358 return 1;
jack__zen 0:a47e8ec71a4e 359 }
jack__zen 0:a47e8ec71a4e 360
jack__zen 0:a47e8ec71a4e 361 // The 1-Wire CRC scheme is described in Maxim Application Note 27:
jack__zen 0:a47e8ec71a4e 362 // "Understanding and Using Cyclic Redundancy Checks with Maxim iButton Products"
jack__zen 0:a47e8ec71a4e 363 //
jack__zen 0:a47e8ec71a4e 364
jack__zen 0:a47e8ec71a4e 365 #if ONEWIRE_CRC8_TABLE
jack__zen 0:a47e8ec71a4e 366 // This table comes from Dallas sample code where it is freely reusable,
jack__zen 0:a47e8ec71a4e 367 // though Copyright (C) 2000 Dallas Semiconductor Corporation
jack__zen 0:a47e8ec71a4e 368 static BYTE dscrc_table[] =
jack__zen 0:a47e8ec71a4e 369 {
jack__zen 0:a47e8ec71a4e 370 0, 94,188,226, 97, 63,221,131,194,156,126, 32,163,253, 31, 65,
jack__zen 0:a47e8ec71a4e 371 157,195, 33,127,252,162, 64, 30, 95, 1,227,189, 62, 96,130,220,
jack__zen 0:a47e8ec71a4e 372 35,125,159,193, 66, 28,254,160,225,191, 93, 3,128,222, 60, 98,
jack__zen 0:a47e8ec71a4e 373 190,224, 2, 92,223,129, 99, 61,124, 34,192,158, 29, 67,161,255,
jack__zen 0:a47e8ec71a4e 374 70, 24,250,164, 39,121,155,197,132,218, 56,102,229,187, 89, 7,
jack__zen 0:a47e8ec71a4e 375 219,133,103, 57,186,228, 6, 88, 25, 71,165,251,120, 38,196,154,
jack__zen 0:a47e8ec71a4e 376 101, 59,217,135, 4, 90,184,230,167,249, 27, 69,198,152,122, 36,
jack__zen 0:a47e8ec71a4e 377 248,166, 68, 26,153,199, 37,123, 58,100,134,216, 91, 5,231,185,
jack__zen 0:a47e8ec71a4e 378 140,210, 48,110,237,179, 81, 15, 78, 16,242,172, 47,113,147,205,
jack__zen 0:a47e8ec71a4e 379 17, 79,173,243,112, 46,204,146,211,141,111, 49,178,236, 14, 80,
jack__zen 0:a47e8ec71a4e 380 175,241, 19, 77,206,144,114, 44,109, 51,209,143, 12, 82,176,238,
jack__zen 0:a47e8ec71a4e 381 50,108,142,208, 83, 13,239,177,240,174, 76, 18,145,207, 45,115,
jack__zen 0:a47e8ec71a4e 382 202,148,118, 40,171,245, 23, 73, 8, 86,180,234,105, 55,213,139,
jack__zen 0:a47e8ec71a4e 383 87, 9,235,181, 54,104,138,212,149,203, 41,119,244,170, 72, 22,
jack__zen 0:a47e8ec71a4e 384 233,183, 85, 11,136,214, 52,106, 43,117,151,201, 74, 20,246,168,
jack__zen 0:a47e8ec71a4e 385 116, 42,200,150, 21, 75,169,247,182,232, 10, 84,215,137,107, 53};
jack__zen 0:a47e8ec71a4e 386
jack__zen 0:a47e8ec71a4e 387 //
jack__zen 0:a47e8ec71a4e 388 // Compute a Dallas Semiconductor 8 bit CRC. These show up in the ROM
jack__zen 0:a47e8ec71a4e 389 // and the registers. (note: this might better be done without the
jack__zen 0:a47e8ec71a4e 390 // table, it would probably be smaller and certainly fast enough
jack__zen 0:a47e8ec71a4e 391 // compared to all those delayMicrosecond() calls. But I got
jack__zen 0:a47e8ec71a4e 392 // confused, so I use this table from the examples.)
jack__zen 0:a47e8ec71a4e 393 //
jack__zen 0:a47e8ec71a4e 394 BYTE OneWireCRC::crc8(BYTE* addr, BYTE len)
jack__zen 0:a47e8ec71a4e 395 {
jack__zen 0:a47e8ec71a4e 396 BYTE i;
jack__zen 0:a47e8ec71a4e 397 BYTE crc = 0;
jack__zen 0:a47e8ec71a4e 398
jack__zen 0:a47e8ec71a4e 399 for (i = 0; i < len; i++)
jack__zen 0:a47e8ec71a4e 400 {
jack__zen 0:a47e8ec71a4e 401 crc = dscrc_table[crc ^ addr[i] ];
jack__zen 0:a47e8ec71a4e 402 }
jack__zen 0:a47e8ec71a4e 403
jack__zen 0:a47e8ec71a4e 404 return crc;
jack__zen 0:a47e8ec71a4e 405 }
jack__zen 0:a47e8ec71a4e 406 #else
jack__zen 0:a47e8ec71a4e 407 //
jack__zen 0:a47e8ec71a4e 408 // Compute a Dallas Semiconductor 8 bit CRC directly.
jack__zen 0:a47e8ec71a4e 409 //
jack__zen 0:a47e8ec71a4e 410 BYTE OneWireCRC::crc8(BYTE* addr, BYTE len)
jack__zen 0:a47e8ec71a4e 411 {
jack__zen 0:a47e8ec71a4e 412 BYTE i, j;
jack__zen 0:a47e8ec71a4e 413 BYTE crc = 0;
jack__zen 0:a47e8ec71a4e 414
jack__zen 0:a47e8ec71a4e 415 for (i = 0; i < len; i++)
jack__zen 0:a47e8ec71a4e 416 {
jack__zen 0:a47e8ec71a4e 417 BYTE inbyte = addr[i];
jack__zen 0:a47e8ec71a4e 418 for (j = 0; j < 8; j++)
jack__zen 0:a47e8ec71a4e 419 {
jack__zen 0:a47e8ec71a4e 420 BYTE mix = (crc ^ inbyte) & 0x01;
jack__zen 0:a47e8ec71a4e 421 crc >>= 1;
jack__zen 0:a47e8ec71a4e 422 if (mix) crc ^= 0x8C;
jack__zen 0:a47e8ec71a4e 423 inbyte >>= 1;
jack__zen 0:a47e8ec71a4e 424 }
jack__zen 0:a47e8ec71a4e 425 }
jack__zen 0:a47e8ec71a4e 426
jack__zen 0:a47e8ec71a4e 427 return crc;
jack__zen 0:a47e8ec71a4e 428 }
jack__zen 0:a47e8ec71a4e 429 #endif
jack__zen 0:a47e8ec71a4e 430
jack__zen 0:a47e8ec71a4e 431 static short oddparity[16] = { 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0 };
jack__zen 0:a47e8ec71a4e 432
jack__zen 0:a47e8ec71a4e 433 //
jack__zen 0:a47e8ec71a4e 434 // Compute a Dallas Semiconductor 16 bit CRC. I have never seen one of
jack__zen 0:a47e8ec71a4e 435 // these, but here it is.
jack__zen 0:a47e8ec71a4e 436 //
jack__zen 0:a47e8ec71a4e 437 unsigned short OneWireCRC::crc16(unsigned short* data, unsigned short len)
jack__zen 0:a47e8ec71a4e 438 {
jack__zen 0:a47e8ec71a4e 439 unsigned short i;
jack__zen 0:a47e8ec71a4e 440 unsigned short crc = 0;
jack__zen 0:a47e8ec71a4e 441
jack__zen 0:a47e8ec71a4e 442 for ( i = 0; i < len; i++)
jack__zen 0:a47e8ec71a4e 443 {
jack__zen 0:a47e8ec71a4e 444 unsigned short cdata = data[len];
jack__zen 0:a47e8ec71a4e 445
jack__zen 0:a47e8ec71a4e 446 cdata = (cdata ^ (crc & 0xff)) & 0xff;
jack__zen 0:a47e8ec71a4e 447 crc >>= 8;
jack__zen 0:a47e8ec71a4e 448
jack__zen 0:a47e8ec71a4e 449 if (oddparity[cdata & 0xf] ^ oddparity[cdata >> 4]) crc ^= 0xc001;
jack__zen 0:a47e8ec71a4e 450
jack__zen 0:a47e8ec71a4e 451 cdata <<= 6;
jack__zen 0:a47e8ec71a4e 452 crc ^= cdata;
jack__zen 0:a47e8ec71a4e 453 cdata <<= 1;
jack__zen 0:a47e8ec71a4e 454 crc ^= cdata;
jack__zen 0:a47e8ec71a4e 455 }
jack__zen 0:a47e8ec71a4e 456
jack__zen 0:a47e8ec71a4e 457 return crc;
jack__zen 0:a47e8ec71a4e 458 }
jack__zen 0:a47e8ec71a4e 459