Lucian Corduneanu / OneWire

Dallas' 1-Wire bus protocol library using mbed debug logs

Fork of OneWire by Zoltan Hudak

OneWire.cpp@2:e651dfd17be2, 2015-10-28 (annotated)

Committer:
hudakz
Date:
Wed Oct 28 17:50:07 2015 +0000
Revision:
2:e651dfd17be2
Parent:
0:acf75feb0947
Child:
4:68746e80003d
read_bit function timing tuned

Who changed what in which revision?

UserRevisionLine numberNew contents of line
hudakz 0:acf75feb0947 1 /*
hudakz 0:acf75feb0947 2 Copyright (c) 2007, Jim Studt (original old version - many contributors since)
hudakz 0:acf75feb0947 3
hudakz 0:acf75feb0947 4 The latest version of this library may be found at:
hudakz 0:acf75feb0947 5 http://www.pjrc.com/teensy/td_libs_OneWire.html
hudakz 0:acf75feb0947 6
hudakz 0:acf75feb0947 7 OneWire has been maintained by Paul Stoffregen (paul@pjrc.com) since
hudakz 0:acf75feb0947 8 January 2010. At the time, it was in need of many bug fixes, but had
hudakz 0:acf75feb0947 9 been abandoned the original author (Jim Studt). None of the known
hudakz 0:acf75feb0947 10 contributors were interested in maintaining OneWire. Paul typically
hudakz 0:acf75feb0947 11 works on OneWire every 6 to 12 months. Patches usually wait that
hudakz 0:acf75feb0947 12 long. If anyone is interested in more actively maintaining OneWire,
hudakz 0:acf75feb0947 13 please contact Paul.
hudakz 0:acf75feb0947 14
hudakz 0:acf75feb0947 15 Version 2.2:
hudakz 0:acf75feb0947 16 Teensy 3.0 compatibility, Paul Stoffregen, paul@pjrc.com
hudakz 0:acf75feb0947 17 Arduino Due compatibility, http://arduino.cc/forum/index.php?topic=141030
hudakz 0:acf75feb0947 18 Fix DS18B20 example negative temperature
hudakz 0:acf75feb0947 19 Fix DS18B20 example's low res modes, Ken Butcher
hudakz 0:acf75feb0947 20 Improve reset timing, Mark Tillotson
hudakz 0:acf75feb0947 21 Add const qualifiers, Bertrik Sikken
hudakz 0:acf75feb0947 22 Add initial value input to crc16, Bertrik Sikken
hudakz 0:acf75feb0947 23 Add target_search() function, Scott Roberts
hudakz 0:acf75feb0947 24
hudakz 0:acf75feb0947 25 Version 2.1:
hudakz 0:acf75feb0947 26 Arduino 1.0 compatibility, Paul Stoffregen
hudakz 0:acf75feb0947 27 Improve temperature example, Paul Stoffregen
hudakz 0:acf75feb0947 28 DS250x_PROM example, Guillermo Lovato
hudakz 0:acf75feb0947 29 PIC32 (chipKit) compatibility, Jason Dangel, dangel.jason AT gmail.com
hudakz 0:acf75feb0947 30 Improvements from Glenn Trewitt:
hudakz 0:acf75feb0947 31 - crc16() now works
hudakz 0:acf75feb0947 32 - check_crc16() does all of calculation/checking work.
hudakz 0:acf75feb0947 33 - Added read_bytes() and write_bytes(), to reduce tedious loops.
hudakz 0:acf75feb0947 34 - Added ds2408 example.
hudakz 0:acf75feb0947 35 Delete very old, out-of-date readme file (info is here)
hudakz 0:acf75feb0947 36
hudakz 0:acf75feb0947 37 Version 2.0: Modifications by Paul Stoffregen, January 2010:
hudakz 0:acf75feb0947 38 http://www.pjrc.com/teensy/td_libs_OneWire.html
hudakz 0:acf75feb0947 39 Search fix from Robin James
hudakz 0:acf75feb0947 40 http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1238032295/27#27
hudakz 0:acf75feb0947 41 Use direct optimized I/O in all cases
hudakz 0:acf75feb0947 42 Disable interrupts during timing critical sections
hudakz 0:acf75feb0947 43 (this solves many random communication errors)
hudakz 0:acf75feb0947 44 Disable interrupts during read-modify-write I/O
hudakz 0:acf75feb0947 45 Reduce RAM consumption by eliminating unnecessary
hudakz 0:acf75feb0947 46 variables and trimming many to 8 bits
hudakz 0:acf75feb0947 47 Optimize both crc8 - table version moved to flash
hudakz 0:acf75feb0947 48
hudakz 0:acf75feb0947 49 Modified to work with larger numbers of devices - avoids loop.
hudakz 0:acf75feb0947 50 Tested in Arduino 11 alpha with 12 sensors.
hudakz 0:acf75feb0947 51 26 Sept 2008 -- Robin James
hudakz 0:acf75feb0947 52 http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1238032295/27#27
hudakz 0:acf75feb0947 53
hudakz 0:acf75feb0947 54 Updated to work with arduino-0008 and to include skip() as of
hudakz 0:acf75feb0947 55 2007/07/06. --RJL20
hudakz 0:acf75feb0947 56
hudakz 0:acf75feb0947 57 Modified to calculate the 8-bit CRC directly, avoiding the need for
hudakz 0:acf75feb0947 58 the 256-byte lookup table to be loaded in RAM. Tested in arduino-0010
hudakz 0:acf75feb0947 59 -- Tom Pollard, Jan 23, 2008
hudakz 0:acf75feb0947 60
hudakz 0:acf75feb0947 61 Jim Studt's original library was modified by Josh Larios.
hudakz 0:acf75feb0947 62
hudakz 0:acf75feb0947 63 Tom Pollard, pollard@alum.mit.edu, contributed around May 20, 2008
hudakz 0:acf75feb0947 64
hudakz 0:acf75feb0947 65 Permission is hereby granted, free of charge, to any person obtaining
hudakz 0:acf75feb0947 66 a copy of this software and associated documentation files (the
hudakz 0:acf75feb0947 67 "Software"), to deal in the Software without restriction, including
hudakz 0:acf75feb0947 68 without limitation the rights to use, copy, modify, merge, publish,
hudakz 0:acf75feb0947 69 distribute, sublicense, and/or sell copies of the Software, and to
hudakz 0:acf75feb0947 70 permit persons to whom the Software is furnished to do so, subject to
hudakz 0:acf75feb0947 71 the following conditions:
hudakz 0:acf75feb0947 72
hudakz 0:acf75feb0947 73 The above copyright notice and this permission notice shall be
hudakz 0:acf75feb0947 74 included in all copies or substantial portions of the Software.
hudakz 0:acf75feb0947 75
hudakz 0:acf75feb0947 76 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
hudakz 0:acf75feb0947 77 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
hudakz 0:acf75feb0947 78 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
hudakz 0:acf75feb0947 79 NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
hudakz 0:acf75feb0947 80 LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
hudakz 0:acf75feb0947 81 OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
hudakz 0:acf75feb0947 82 WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
hudakz 0:acf75feb0947 83
hudakz 0:acf75feb0947 84 Much of the code was inspired by Derek Yerger's code, though I don't
hudakz 0:acf75feb0947 85 think much of that remains. In any event that was..
hudakz 0:acf75feb0947 86 (copyleft) 2006 by Derek Yerger - Free to distribute freely.
hudakz 0:acf75feb0947 87
hudakz 0:acf75feb0947 88 The CRC code was excerpted and inspired by the Dallas Semiconductor
hudakz 0:acf75feb0947 89 sample code bearing this copyright.
hudakz 0:acf75feb0947 90 //---------------------------------------------------------------------------
hudakz 0:acf75feb0947 91 // Copyright (C) 2000 Dallas Semiconductor Corporation, All Rights Reserved.
hudakz 0:acf75feb0947 92 //
hudakz 0:acf75feb0947 93 // Permission is hereby granted, free of charge, to any person obtaining a
hudakz 0:acf75feb0947 94 // copy of this software and associated documentation files (the "Software"),
hudakz 0:acf75feb0947 95 // to deal in the Software without restriction, including without limitation
hudakz 0:acf75feb0947 96 // the rights to use, copy, modify, merge, publish, distribute, sublicense,
hudakz 0:acf75feb0947 97 // and/or sell copies of the Software, and to permit persons to whom the
hudakz 0:acf75feb0947 98 // Software is furnished to do so, subject to the following conditions:
hudakz 0:acf75feb0947 99 //
hudakz 0:acf75feb0947 100 // The above copyright notice and this permission notice shall be included
hudakz 0:acf75feb0947 101 // in all copies or substantial portions of the Software.
hudakz 0:acf75feb0947 102 //
hudakz 0:acf75feb0947 103 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
hudakz 0:acf75feb0947 104 // OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
hudakz 0:acf75feb0947 105 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
hudakz 0:acf75feb0947 106 // IN NO EVENT SHALL DALLAS SEMICONDUCTOR BE LIABLE FOR ANY CLAIM, DAMAGES
hudakz 0:acf75feb0947 107 // OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
hudakz 0:acf75feb0947 108 // ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
hudakz 0:acf75feb0947 109 // OTHER DEALINGS IN THE SOFTWARE.
hudakz 0:acf75feb0947 110 //
hudakz 0:acf75feb0947 111 // Except as contained in this notice, the name of Dallas Semiconductor
hudakz 0:acf75feb0947 112 // shall not be used except as stated in the Dallas Semiconductor
hudakz 0:acf75feb0947 113 // Branding Policy.
hudakz 0:acf75feb0947 114 //--------------------------------------------------------------------------
hudakz 0:acf75feb0947 115 */
hudakz 0:acf75feb0947 116
hudakz 0:acf75feb0947 117 #include "OneWire.h"
hudakz 0:acf75feb0947 118
hudakz 0:acf75feb0947 119 OneWire::OneWire(PinName pin):
hudakz 0:acf75feb0947 120 wire(pin)
hudakz 0:acf75feb0947 121 {
hudakz 0:acf75feb0947 122 #if ONEWIRE_SEARCH
hudakz 0:acf75feb0947 123 reset_search();
hudakz 0:acf75feb0947 124 #endif
hudakz 0:acf75feb0947 125 }
hudakz 0:acf75feb0947 126
hudakz 0:acf75feb0947 127
hudakz 0:acf75feb0947 128 // Perform the onewire reset function. We will wait up to 250uS for
hudakz 0:acf75feb0947 129 // the bus to come high, if it doesn't then it is broken or shorted
hudakz 0:acf75feb0947 130 // and we return a 0;
hudakz 0:acf75feb0947 131 //
hudakz 0:acf75feb0947 132 // Returns 1 if a device asserted a presence pulse, 0 otherwise.
hudakz 0:acf75feb0947 133 //
hudakz 0:acf75feb0947 134 uint8_t OneWire::reset(void)
hudakz 0:acf75feb0947 135 {
hudakz 0:acf75feb0947 136 uint8_t r;
hudakz 0:acf75feb0947 137 uint8_t retries = 125;
hudakz 0:acf75feb0947 138
hudakz 0:acf75feb0947 139 wire.input();
hudakz 0:acf75feb0947 140 // wait until the wire is high... just in case
hudakz 0:acf75feb0947 141 do {
hudakz 0:acf75feb0947 142 if (--retries == 0) {
hudakz 0:acf75feb0947 143 return 0;
hudakz 0:acf75feb0947 144 }
hudakz 0:acf75feb0947 145 wait_us(2);
hudakz 0:acf75feb0947 146 } while (wire.read() != 1);
hudakz 0:acf75feb0947 147
hudakz 0:acf75feb0947 148 wire.output();
hudakz 0:acf75feb0947 149 wire = 0;
hudakz 0:acf75feb0947 150 wait_us(480);
hudakz 0:acf75feb0947 151 wire.input();
hudakz 0:acf75feb0947 152 wait_us(70);
hudakz 0:acf75feb0947 153 r = !wire.read();
hudakz 0:acf75feb0947 154 wait_us(410);
hudakz 0:acf75feb0947 155 return r;
hudakz 0:acf75feb0947 156 }
hudakz 0:acf75feb0947 157
hudakz 0:acf75feb0947 158 //
hudakz 0:acf75feb0947 159 // Write a bit. Port and bit is used to cut lookup time and provide
hudakz 0:acf75feb0947 160 // more certain timing.
hudakz 0:acf75feb0947 161 //
hudakz 0:acf75feb0947 162 void OneWire::write_bit(uint8_t v)
hudakz 0:acf75feb0947 163 {
hudakz 0:acf75feb0947 164 wire.output();
hudakz 0:acf75feb0947 165 if (v & 1) {
hudakz 0:acf75feb0947 166 wire = 0; // drive output low
hudakz 0:acf75feb0947 167 wait_us(10);
hudakz 0:acf75feb0947 168 wire = 1; // drive output high
hudakz 0:acf75feb0947 169 wait_us(55);
hudakz 0:acf75feb0947 170 } else {
hudakz 0:acf75feb0947 171 wire = 0; // drive output low
hudakz 0:acf75feb0947 172 wait_us(65);
hudakz 0:acf75feb0947 173 wire = 1; // drive output high
hudakz 0:acf75feb0947 174 wait_us(5);
hudakz 0:acf75feb0947 175 }
hudakz 0:acf75feb0947 176 }
hudakz 0:acf75feb0947 177
hudakz 0:acf75feb0947 178 //
hudakz 0:acf75feb0947 179 // Read a bit. Port and bit is used to cut lookup time and provide
hudakz 0:acf75feb0947 180 // more certain timing.
hudakz 0:acf75feb0947 181 //
hudakz 0:acf75feb0947 182 uint8_t OneWire::read_bit(void)
hudakz 0:acf75feb0947 183 {
hudakz 0:acf75feb0947 184 uint8_t r;
hudakz 0:acf75feb0947 185
hudakz 0:acf75feb0947 186 wire.output();
hudakz 0:acf75feb0947 187 wire = 0;
hudakz 2:e651dfd17be2 188 wait_us(1);
hudakz 0:acf75feb0947 189 wire.input();
hudakz 2:e651dfd17be2 190 wait_us(6);
hudakz 0:acf75feb0947 191 r = wire.read();
hudakz 0:acf75feb0947 192 wait_us(54);
hudakz 0:acf75feb0947 193 return r;
hudakz 0:acf75feb0947 194 }
hudakz 0:acf75feb0947 195
hudakz 0:acf75feb0947 196 //
hudakz 0:acf75feb0947 197 // Write a byte. The writing code uses the active drivers to raise the
hudakz 0:acf75feb0947 198 // pin high, if you need power after the write (e.g. DS18S20 in
hudakz 0:acf75feb0947 199 // parasite power mode) then set 'power' to 1, otherwise the pin will
hudakz 0:acf75feb0947 200 // go tri-state at the end of the write to avoid heating in a short or
hudakz 0:acf75feb0947 201 // other mishap.
hudakz 0:acf75feb0947 202 //
hudakz 0:acf75feb0947 203 void OneWire::write(uint8_t v, uint8_t power /* = 0 */) {
hudakz 0:acf75feb0947 204 uint8_t bitMask;
hudakz 0:acf75feb0947 205
hudakz 0:acf75feb0947 206 for (bitMask = 0x01; bitMask; bitMask <<= 1) {
hudakz 0:acf75feb0947 207 OneWire::write_bit( (bitMask & v)?1:0);
hudakz 0:acf75feb0947 208 }
hudakz 0:acf75feb0947 209 if ( !power) {
hudakz 0:acf75feb0947 210 wire.input();
hudakz 0:acf75feb0947 211 }
hudakz 0:acf75feb0947 212 }
hudakz 0:acf75feb0947 213
hudakz 0:acf75feb0947 214 void OneWire::write_bytes(const uint8_t *buf, uint16_t count, bool power /* = 0 */) {
hudakz 0:acf75feb0947 215 for (uint16_t i = 0 ; i < count ; i++)
hudakz 0:acf75feb0947 216 write(buf[i]);
hudakz 0:acf75feb0947 217 if (!power) {
hudakz 0:acf75feb0947 218 wire.input();
hudakz 0:acf75feb0947 219 }
hudakz 0:acf75feb0947 220 }
hudakz 0:acf75feb0947 221
hudakz 0:acf75feb0947 222 //
hudakz 0:acf75feb0947 223 // Read a byte
hudakz 0:acf75feb0947 224 //
hudakz 0:acf75feb0947 225 uint8_t OneWire::read() {
hudakz 0:acf75feb0947 226 uint8_t bitMask;
hudakz 0:acf75feb0947 227 uint8_t r = 0;
hudakz 0:acf75feb0947 228
hudakz 0:acf75feb0947 229 for (bitMask = 0x01; bitMask; bitMask <<= 1) {
hudakz 0:acf75feb0947 230 if ( OneWire::read_bit()) r |= bitMask;
hudakz 0:acf75feb0947 231 }
hudakz 0:acf75feb0947 232 return r;
hudakz 0:acf75feb0947 233 }
hudakz 0:acf75feb0947 234
hudakz 0:acf75feb0947 235 void OneWire::read_bytes(uint8_t *buf, uint16_t count) {
hudakz 0:acf75feb0947 236 for (uint16_t i = 0 ; i < count ; i++)
hudakz 0:acf75feb0947 237 buf[i] = read();
hudakz 0:acf75feb0947 238 }
hudakz 0:acf75feb0947 239
hudakz 0:acf75feb0947 240 //
hudakz 0:acf75feb0947 241 // Do a ROM select
hudakz 0:acf75feb0947 242 //
hudakz 0:acf75feb0947 243 void OneWire::select(const uint8_t rom[8])
hudakz 0:acf75feb0947 244 {
hudakz 0:acf75feb0947 245 uint8_t i;
hudakz 0:acf75feb0947 246
hudakz 0:acf75feb0947 247 write(0x55); // Choose ROM
hudakz 0:acf75feb0947 248
hudakz 0:acf75feb0947 249 for (i = 0; i < 8; i++) write(rom[i]);
hudakz 0:acf75feb0947 250 }
hudakz 0:acf75feb0947 251
hudakz 0:acf75feb0947 252 //
hudakz 0:acf75feb0947 253 // Do a ROM skip
hudakz 0:acf75feb0947 254 //
hudakz 0:acf75feb0947 255 void OneWire::skip()
hudakz 0:acf75feb0947 256 {
hudakz 0:acf75feb0947 257 write(0xCC); // Skip ROM
hudakz 0:acf75feb0947 258 }
hudakz 0:acf75feb0947 259
hudakz 0:acf75feb0947 260 void OneWire::depower()
hudakz 0:acf75feb0947 261 {
hudakz 0:acf75feb0947 262 wire.input();
hudakz 0:acf75feb0947 263 }
hudakz 0:acf75feb0947 264
hudakz 0:acf75feb0947 265 #if ONEWIRE_SEARCH
hudakz 0:acf75feb0947 266
hudakz 0:acf75feb0947 267 //
hudakz 0:acf75feb0947 268 // You need to use this function to start a search again from the beginning.
hudakz 0:acf75feb0947 269 // You do not need to do it for the first search, though you could.
hudakz 0:acf75feb0947 270 //
hudakz 0:acf75feb0947 271 void OneWire::reset_search()
hudakz 0:acf75feb0947 272 {
hudakz 0:acf75feb0947 273 // reset the search state
hudakz 0:acf75feb0947 274 LastDiscrepancy = 0;
hudakz 0:acf75feb0947 275 LastDeviceFlag = false;
hudakz 0:acf75feb0947 276 LastFamilyDiscrepancy = 0;
hudakz 0:acf75feb0947 277 for(int i = 7; ; i--) {
hudakz 0:acf75feb0947 278 ROM_NO[i] = 0;
hudakz 0:acf75feb0947 279 if ( i == 0) break;
hudakz 0:acf75feb0947 280 }
hudakz 0:acf75feb0947 281 }
hudakz 0:acf75feb0947 282
hudakz 0:acf75feb0947 283 // Setup the search to find the device type 'family_code' on the next call
hudakz 0:acf75feb0947 284 // to search(*newAddr) if it is present.
hudakz 0:acf75feb0947 285 //
hudakz 0:acf75feb0947 286 void OneWire::target_search(uint8_t family_code)
hudakz 0:acf75feb0947 287 {
hudakz 0:acf75feb0947 288 // set the search state to find SearchFamily type devices
hudakz 0:acf75feb0947 289 ROM_NO[0] = family_code;
hudakz 0:acf75feb0947 290 for (uint8_t i = 1; i < 8; i++)
hudakz 0:acf75feb0947 291 ROM_NO[i] = 0;
hudakz 0:acf75feb0947 292 LastDiscrepancy = 64;
hudakz 0:acf75feb0947 293 LastFamilyDiscrepancy = 0;
hudakz 0:acf75feb0947 294 LastDeviceFlag = false;
hudakz 0:acf75feb0947 295 }
hudakz 0:acf75feb0947 296
hudakz 0:acf75feb0947 297 //
hudakz 0:acf75feb0947 298 // Perform a search. If this function returns a '1' then it has
hudakz 0:acf75feb0947 299 // enumerated the next device and you may retrieve the ROM from the
hudakz 0:acf75feb0947 300 // OneWire::address variable. If there are no devices, no further
hudakz 0:acf75feb0947 301 // devices, or something horrible happens in the middle of the
hudakz 0:acf75feb0947 302 // enumeration then a 0 is returned. If a new device is found then
hudakz 0:acf75feb0947 303 // its address is copied to newAddr. Use OneWire::reset_search() to
hudakz 0:acf75feb0947 304 // start over.
hudakz 0:acf75feb0947 305 //
hudakz 0:acf75feb0947 306 // --- Replaced by the one from the Dallas Semiconductor web site ---
hudakz 0:acf75feb0947 307 //--------------------------------------------------------------------------
hudakz 0:acf75feb0947 308 // Perform the 1-Wire Search Algorithm on the 1-Wire bus using the existing
hudakz 0:acf75feb0947 309 // search state.
hudakz 0:acf75feb0947 310 // Return true : device found, ROM number in ROM_NO buffer
hudakz 0:acf75feb0947 311 // false : device not found, end of search
hudakz 0:acf75feb0947 312 //
hudakz 0:acf75feb0947 313 uint8_t OneWire::search(uint8_t *newAddr)
hudakz 0:acf75feb0947 314 {
hudakz 0:acf75feb0947 315 uint8_t id_bit_number;
hudakz 0:acf75feb0947 316 uint8_t last_zero, rom_byte_number, search_result;
hudakz 0:acf75feb0947 317 uint8_t id_bit, cmp_id_bit;
hudakz 0:acf75feb0947 318
hudakz 0:acf75feb0947 319 unsigned char rom_byte_mask, search_direction;
hudakz 0:acf75feb0947 320
hudakz 0:acf75feb0947 321 // initialize for search
hudakz 0:acf75feb0947 322 id_bit_number = 1;
hudakz 0:acf75feb0947 323 last_zero = 0;
hudakz 0:acf75feb0947 324 rom_byte_number = 0;
hudakz 0:acf75feb0947 325 rom_byte_mask = 1;
hudakz 0:acf75feb0947 326 search_result = 0;
hudakz 0:acf75feb0947 327
hudakz 0:acf75feb0947 328 // if the last call was not the last one
hudakz 0:acf75feb0947 329 if (!LastDeviceFlag)
hudakz 0:acf75feb0947 330 {
hudakz 0:acf75feb0947 331 // 1-Wire reset
hudakz 0:acf75feb0947 332 if (!reset())
hudakz 0:acf75feb0947 333 {
hudakz 0:acf75feb0947 334 // reset the search
hudakz 0:acf75feb0947 335 LastDiscrepancy = 0;
hudakz 0:acf75feb0947 336 LastDeviceFlag = false;
hudakz 0:acf75feb0947 337 LastFamilyDiscrepancy = 0;
hudakz 0:acf75feb0947 338 return false;
hudakz 0:acf75feb0947 339 }
hudakz 0:acf75feb0947 340
hudakz 0:acf75feb0947 341 // issue the search command
hudakz 0:acf75feb0947 342 write(0xF0);
hudakz 0:acf75feb0947 343
hudakz 0:acf75feb0947 344 // loop to do the search
hudakz 0:acf75feb0947 345 do
hudakz 0:acf75feb0947 346 {
hudakz 0:acf75feb0947 347 // read a bit and its complement
hudakz 0:acf75feb0947 348 id_bit = read_bit();
hudakz 0:acf75feb0947 349 cmp_id_bit = read_bit();
hudakz 0:acf75feb0947 350
hudakz 0:acf75feb0947 351 // check for no devices on 1-wire
hudakz 0:acf75feb0947 352 if ((id_bit == 1) && (cmp_id_bit == 1))
hudakz 0:acf75feb0947 353 break;
hudakz 0:acf75feb0947 354 else
hudakz 0:acf75feb0947 355 {
hudakz 0:acf75feb0947 356 // all devices coupled have 0 or 1
hudakz 0:acf75feb0947 357 if (id_bit != cmp_id_bit)
hudakz 0:acf75feb0947 358 search_direction = id_bit; // bit write value for search
hudakz 0:acf75feb0947 359 else
hudakz 0:acf75feb0947 360 {
hudakz 0:acf75feb0947 361 // if this discrepancy if before the Last Discrepancy
hudakz 0:acf75feb0947 362 // on a previous next then pick the same as last time
hudakz 0:acf75feb0947 363 if (id_bit_number < LastDiscrepancy)
hudakz 0:acf75feb0947 364 search_direction = ((ROM_NO[rom_byte_number] & rom_byte_mask) > 0);
hudakz 0:acf75feb0947 365 else
hudakz 0:acf75feb0947 366 // if equal to last pick 1, if not then pick 0
hudakz 0:acf75feb0947 367 search_direction = (id_bit_number == LastDiscrepancy);
hudakz 0:acf75feb0947 368
hudakz 0:acf75feb0947 369 // if 0 was picked then record its position in LastZero
hudakz 0:acf75feb0947 370 if (search_direction == 0)
hudakz 0:acf75feb0947 371 {
hudakz 0:acf75feb0947 372 last_zero = id_bit_number;
hudakz 0:acf75feb0947 373
hudakz 0:acf75feb0947 374 // check for Last discrepancy in family
hudakz 0:acf75feb0947 375 if (last_zero < 9)
hudakz 0:acf75feb0947 376 LastFamilyDiscrepancy = last_zero;
hudakz 0:acf75feb0947 377 }
hudakz 0:acf75feb0947 378 }
hudakz 0:acf75feb0947 379
hudakz 0:acf75feb0947 380 // set or clear the bit in the ROM byte rom_byte_number
hudakz 0:acf75feb0947 381 // with mask rom_byte_mask
hudakz 0:acf75feb0947 382 if (search_direction == 1)
hudakz 0:acf75feb0947 383 ROM_NO[rom_byte_number] |= rom_byte_mask;
hudakz 0:acf75feb0947 384 else
hudakz 0:acf75feb0947 385 ROM_NO[rom_byte_number] &= ~rom_byte_mask;
hudakz 0:acf75feb0947 386
hudakz 0:acf75feb0947 387 // serial number search direction write bit
hudakz 0:acf75feb0947 388 write_bit(search_direction);
hudakz 0:acf75feb0947 389
hudakz 0:acf75feb0947 390 // increment the byte counter id_bit_number
hudakz 0:acf75feb0947 391 // and shift the mask rom_byte_mask
hudakz 0:acf75feb0947 392 id_bit_number++;
hudakz 0:acf75feb0947 393 rom_byte_mask <<= 1;
hudakz 0:acf75feb0947 394
hudakz 0:acf75feb0947 395 // if the mask is 0 then go to new SerialNum byte rom_byte_number and reset mask
hudakz 0:acf75feb0947 396 if (rom_byte_mask == 0)
hudakz 0:acf75feb0947 397 {
hudakz 0:acf75feb0947 398 rom_byte_number++;
hudakz 0:acf75feb0947 399 rom_byte_mask = 1;
hudakz 0:acf75feb0947 400 }
hudakz 0:acf75feb0947 401 }
hudakz 0:acf75feb0947 402 }
hudakz 0:acf75feb0947 403 while(rom_byte_number < 8); // loop until through all ROM bytes 0-7
hudakz 0:acf75feb0947 404
hudakz 0:acf75feb0947 405 // if the search was successful then
hudakz 0:acf75feb0947 406 if (!(id_bit_number < 65))
hudakz 0:acf75feb0947 407 {
hudakz 0:acf75feb0947 408 // search successful so set LastDiscrepancy,LastDeviceFlag,search_result
hudakz 0:acf75feb0947 409 LastDiscrepancy = last_zero;
hudakz 0:acf75feb0947 410
hudakz 0:acf75feb0947 411 // check for last device
hudakz 0:acf75feb0947 412 if (LastDiscrepancy == 0)
hudakz 0:acf75feb0947 413 LastDeviceFlag = true;
hudakz 0:acf75feb0947 414
hudakz 0:acf75feb0947 415 search_result = true;
hudakz 0:acf75feb0947 416 }
hudakz 0:acf75feb0947 417 }
hudakz 0:acf75feb0947 418
hudakz 0:acf75feb0947 419 // if no device found then reset counters so next 'search' will be like a first
hudakz 0:acf75feb0947 420 if (!search_result || !ROM_NO[0])
hudakz 0:acf75feb0947 421 {
hudakz 0:acf75feb0947 422 LastDiscrepancy = 0;
hudakz 0:acf75feb0947 423 LastDeviceFlag = false;
hudakz 0:acf75feb0947 424 LastFamilyDiscrepancy = 0;
hudakz 0:acf75feb0947 425 search_result = false;
hudakz 0:acf75feb0947 426 }
hudakz 0:acf75feb0947 427 for (int i = 0; i < 8; i++) newAddr[i] = ROM_NO[i];
hudakz 0:acf75feb0947 428 return search_result;
hudakz 0:acf75feb0947 429 }
hudakz 0:acf75feb0947 430
hudakz 0:acf75feb0947 431 #endif
hudakz 0:acf75feb0947 432
hudakz 0:acf75feb0947 433 #if ONEWIRE_CRC
hudakz 0:acf75feb0947 434 // The 1-Wire CRC scheme is described in Maxim Application Note 27:
hudakz 0:acf75feb0947 435 // "Understanding and Using Cyclic Redundancy Checks with Maxim iButton Products"
hudakz 0:acf75feb0947 436 // Compute a Dallas Semiconductor 8 bit CRC directly.
hudakz 0:acf75feb0947 437 //
hudakz 0:acf75feb0947 438 uint8_t OneWire::crc8(const uint8_t *addr, uint8_t len)
hudakz 0:acf75feb0947 439 {
hudakz 0:acf75feb0947 440 uint8_t crc = 0;
hudakz 0:acf75feb0947 441
hudakz 0:acf75feb0947 442 while (len--) {
hudakz 0:acf75feb0947 443 uint8_t inbyte = *addr++;
hudakz 0:acf75feb0947 444 for (uint8_t i = 8; i; i--) {
hudakz 0:acf75feb0947 445 uint8_t mix = (crc ^ inbyte) & 0x01;
hudakz 0:acf75feb0947 446 crc >>= 1;
hudakz 0:acf75feb0947 447 if (mix) crc ^= 0x8C;
hudakz 0:acf75feb0947 448 inbyte >>= 1;
hudakz 0:acf75feb0947 449 }
hudakz 0:acf75feb0947 450 }
hudakz 0:acf75feb0947 451 return crc;
hudakz 0:acf75feb0947 452 }
hudakz 0:acf75feb0947 453 #endif