Zoltan Hudak / OneWire

Dallas' 1-Wire bus protocol library

Dependents:   DS1825 DISCO-F746-Dessiccateur-V1 watersenor_and_temp_code DS1820 ... more

OneWire.cpp@6:d6e084297fb9, 2019-01-20 (annotated)

Committer:
hudakz
Date:
Sun Jan 20 10:10:20 2019 +0000
Revision:
6:d6e084297fb9
Parent:
5:45f3eb39b00c
Child:
7:acf3f0ee66d2
Reading data bits improved.

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 6:d6e084297fb9 188 timer.start();
hudakz 0:acf75feb0947 189 wire.input();
hudakz 6:d6e084297fb9 190 wait_us(12 - timer.read_us());
hudakz 0:acf75feb0947 191 r = wire.read();
hudakz 6:d6e084297fb9 192 timer.stop();
hudakz 6:d6e084297fb9 193 timer.reset();
hudakz 0:acf75feb0947 194 wait_us(54);
hudakz 0:acf75feb0947 195 return r;
hudakz 0:acf75feb0947 196 }
hudakz 0:acf75feb0947 197
hudakz 0:acf75feb0947 198 //
hudakz 0:acf75feb0947 199 // Write a byte. The writing code uses the active drivers to raise the
hudakz 0:acf75feb0947 200 // pin high, if you need power after the write (e.g. DS18S20 in
hudakz 0:acf75feb0947 201 // parasite power mode) then set 'power' to 1, otherwise the pin will
hudakz 0:acf75feb0947 202 // go tri-state at the end of the write to avoid heating in a short or
hudakz 0:acf75feb0947 203 // other mishap.
hudakz 0:acf75feb0947 204 //
hudakz 0:acf75feb0947 205 void OneWire::write(uint8_t v, uint8_t power /* = 0 */) {
hudakz 0:acf75feb0947 206 uint8_t bitMask;
hudakz 0:acf75feb0947 207
hudakz 0:acf75feb0947 208 for (bitMask = 0x01; bitMask; bitMask <<= 1) {
hudakz 0:acf75feb0947 209 OneWire::write_bit( (bitMask & v)?1:0);
hudakz 0:acf75feb0947 210 }
hudakz 0:acf75feb0947 211 if ( !power) {
hudakz 0:acf75feb0947 212 wire.input();
hudakz 0:acf75feb0947 213 }
hudakz 0:acf75feb0947 214 }
hudakz 0:acf75feb0947 215
hudakz 0:acf75feb0947 216 void OneWire::write_bytes(const uint8_t *buf, uint16_t count, bool power /* = 0 */) {
hudakz 0:acf75feb0947 217 for (uint16_t i = 0 ; i < count ; i++)
hudakz 0:acf75feb0947 218 write(buf[i]);
hudakz 0:acf75feb0947 219 if (!power) {
hudakz 0:acf75feb0947 220 wire.input();
hudakz 0:acf75feb0947 221 }
hudakz 0:acf75feb0947 222 }
hudakz 0:acf75feb0947 223
hudakz 0:acf75feb0947 224 //
hudakz 0:acf75feb0947 225 // Read a byte
hudakz 0:acf75feb0947 226 //
hudakz 0:acf75feb0947 227 uint8_t OneWire::read() {
hudakz 0:acf75feb0947 228 uint8_t bitMask;
hudakz 0:acf75feb0947 229 uint8_t r = 0;
hudakz 0:acf75feb0947 230
hudakz 0:acf75feb0947 231 for (bitMask = 0x01; bitMask; bitMask <<= 1) {
hudakz 0:acf75feb0947 232 if ( OneWire::read_bit()) r |= bitMask;
hudakz 0:acf75feb0947 233 }
hudakz 0:acf75feb0947 234 return r;
hudakz 0:acf75feb0947 235 }
hudakz 0:acf75feb0947 236
hudakz 0:acf75feb0947 237 void OneWire::read_bytes(uint8_t *buf, uint16_t count) {
hudakz 0:acf75feb0947 238 for (uint16_t i = 0 ; i < count ; i++)
hudakz 0:acf75feb0947 239 buf[i] = read();
hudakz 0:acf75feb0947 240 }
hudakz 0:acf75feb0947 241
hudakz 0:acf75feb0947 242 //
hudakz 0:acf75feb0947 243 // Do a ROM select
hudakz 0:acf75feb0947 244 //
hudakz 0:acf75feb0947 245 void OneWire::select(const uint8_t rom[8])
hudakz 0:acf75feb0947 246 {
hudakz 0:acf75feb0947 247 uint8_t i;
hudakz 0:acf75feb0947 248
hudakz 0:acf75feb0947 249 write(0x55); // Choose ROM
hudakz 0:acf75feb0947 250
hudakz 0:acf75feb0947 251 for (i = 0; i < 8; i++) write(rom[i]);
hudakz 0:acf75feb0947 252 }
hudakz 0:acf75feb0947 253
hudakz 0:acf75feb0947 254 //
hudakz 0:acf75feb0947 255 // Do a ROM skip
hudakz 0:acf75feb0947 256 //
hudakz 0:acf75feb0947 257 void OneWire::skip()
hudakz 0:acf75feb0947 258 {
hudakz 0:acf75feb0947 259 write(0xCC); // Skip ROM
hudakz 0:acf75feb0947 260 }
hudakz 0:acf75feb0947 261
hudakz 0:acf75feb0947 262 void OneWire::depower()
hudakz 0:acf75feb0947 263 {
hudakz 0:acf75feb0947 264 wire.input();
hudakz 0:acf75feb0947 265 }
hudakz 0:acf75feb0947 266
hudakz 0:acf75feb0947 267 #if ONEWIRE_SEARCH
hudakz 0:acf75feb0947 268
hudakz 0:acf75feb0947 269 //
hudakz 0:acf75feb0947 270 // You need to use this function to start a search again from the beginning.
hudakz 0:acf75feb0947 271 // You do not need to do it for the first search, though you could.
hudakz 0:acf75feb0947 272 //
hudakz 0:acf75feb0947 273 void OneWire::reset_search()
hudakz 0:acf75feb0947 274 {
hudakz 0:acf75feb0947 275 // reset the search state
hudakz 0:acf75feb0947 276 LastDiscrepancy = 0;
hudakz 0:acf75feb0947 277 LastDeviceFlag = false;
hudakz 0:acf75feb0947 278 LastFamilyDiscrepancy = 0;
hudakz 0:acf75feb0947 279 for(int i = 7; ; i--) {
hudakz 0:acf75feb0947 280 ROM_NO[i] = 0;
hudakz 0:acf75feb0947 281 if ( i == 0) break;
hudakz 0:acf75feb0947 282 }
hudakz 0:acf75feb0947 283 }
hudakz 0:acf75feb0947 284
hudakz 0:acf75feb0947 285 // Setup the search to find the device type 'family_code' on the next call
hudakz 0:acf75feb0947 286 // to search(*newAddr) if it is present.
hudakz 0:acf75feb0947 287 //
hudakz 0:acf75feb0947 288 void OneWire::target_search(uint8_t family_code)
hudakz 0:acf75feb0947 289 {
hudakz 0:acf75feb0947 290 // set the search state to find SearchFamily type devices
hudakz 0:acf75feb0947 291 ROM_NO[0] = family_code;
hudakz 0:acf75feb0947 292 for (uint8_t i = 1; i < 8; i++)
hudakz 0:acf75feb0947 293 ROM_NO[i] = 0;
hudakz 0:acf75feb0947 294 LastDiscrepancy = 64;
hudakz 0:acf75feb0947 295 LastFamilyDiscrepancy = 0;
hudakz 0:acf75feb0947 296 LastDeviceFlag = false;
hudakz 0:acf75feb0947 297 }
hudakz 0:acf75feb0947 298
hudakz 0:acf75feb0947 299 //
hudakz 0:acf75feb0947 300 // Perform a search. If this function returns a '1' then it has
hudakz 0:acf75feb0947 301 // enumerated the next device and you may retrieve the ROM from the
hudakz 0:acf75feb0947 302 // OneWire::address variable. If there are no devices, no further
hudakz 0:acf75feb0947 303 // devices, or something horrible happens in the middle of the
hudakz 0:acf75feb0947 304 // enumeration then a 0 is returned. If a new device is found then
hudakz 0:acf75feb0947 305 // its address is copied to newAddr. Use OneWire::reset_search() to
hudakz 0:acf75feb0947 306 // start over.
hudakz 0:acf75feb0947 307 //
hudakz 0:acf75feb0947 308 // --- Replaced by the one from the Dallas Semiconductor web site ---
hudakz 0:acf75feb0947 309 //--------------------------------------------------------------------------
hudakz 0:acf75feb0947 310 // Perform the 1-Wire Search Algorithm on the 1-Wire bus using the existing
hudakz 0:acf75feb0947 311 // search state.
hudakz 0:acf75feb0947 312 // Return true : device found, ROM number in ROM_NO buffer
hudakz 0:acf75feb0947 313 // false : device not found, end of search
hudakz 0:acf75feb0947 314 //
hudakz 0:acf75feb0947 315 uint8_t OneWire::search(uint8_t *newAddr)
hudakz 0:acf75feb0947 316 {
hudakz 0:acf75feb0947 317 uint8_t id_bit_number;
hudakz 0:acf75feb0947 318 uint8_t last_zero, rom_byte_number, search_result;
hudakz 0:acf75feb0947 319 uint8_t id_bit, cmp_id_bit;
hudakz 0:acf75feb0947 320
hudakz 0:acf75feb0947 321 unsigned char rom_byte_mask, search_direction;
hudakz 0:acf75feb0947 322
hudakz 0:acf75feb0947 323 // initialize for search
hudakz 0:acf75feb0947 324 id_bit_number = 1;
hudakz 0:acf75feb0947 325 last_zero = 0;
hudakz 0:acf75feb0947 326 rom_byte_number = 0;
hudakz 0:acf75feb0947 327 rom_byte_mask = 1;
hudakz 0:acf75feb0947 328 search_result = 0;
hudakz 0:acf75feb0947 329
hudakz 0:acf75feb0947 330 // if the last call was not the last one
hudakz 0:acf75feb0947 331 if (!LastDeviceFlag)
hudakz 0:acf75feb0947 332 {
hudakz 0:acf75feb0947 333 // 1-Wire reset
hudakz 0:acf75feb0947 334 if (!reset())
hudakz 0:acf75feb0947 335 {
hudakz 0:acf75feb0947 336 // reset the search
hudakz 0:acf75feb0947 337 LastDiscrepancy = 0;
hudakz 0:acf75feb0947 338 LastDeviceFlag = false;
hudakz 0:acf75feb0947 339 LastFamilyDiscrepancy = 0;
hudakz 0:acf75feb0947 340 return false;
hudakz 0:acf75feb0947 341 }
hudakz 0:acf75feb0947 342
hudakz 0:acf75feb0947 343 // issue the search command
hudakz 0:acf75feb0947 344 write(0xF0);
hudakz 0:acf75feb0947 345
hudakz 0:acf75feb0947 346 // loop to do the search
hudakz 0:acf75feb0947 347 do
hudakz 0:acf75feb0947 348 {
hudakz 0:acf75feb0947 349 // read a bit and its complement
hudakz 0:acf75feb0947 350 id_bit = read_bit();
hudakz 0:acf75feb0947 351 cmp_id_bit = read_bit();
hudakz 0:acf75feb0947 352
hudakz 0:acf75feb0947 353 // check for no devices on 1-wire
hudakz 0:acf75feb0947 354 if ((id_bit == 1) && (cmp_id_bit == 1))
hudakz 0:acf75feb0947 355 break;
hudakz 0:acf75feb0947 356 else
hudakz 0:acf75feb0947 357 {
hudakz 0:acf75feb0947 358 // all devices coupled have 0 or 1
hudakz 0:acf75feb0947 359 if (id_bit != cmp_id_bit)
hudakz 0:acf75feb0947 360 search_direction = id_bit; // bit write value for search
hudakz 0:acf75feb0947 361 else
hudakz 0:acf75feb0947 362 {
hudakz 0:acf75feb0947 363 // if this discrepancy if before the Last Discrepancy
hudakz 0:acf75feb0947 364 // on a previous next then pick the same as last time
hudakz 0:acf75feb0947 365 if (id_bit_number < LastDiscrepancy)
hudakz 0:acf75feb0947 366 search_direction = ((ROM_NO[rom_byte_number] & rom_byte_mask) > 0);
hudakz 0:acf75feb0947 367 else
hudakz 0:acf75feb0947 368 // if equal to last pick 1, if not then pick 0
hudakz 0:acf75feb0947 369 search_direction = (id_bit_number == LastDiscrepancy);
hudakz 0:acf75feb0947 370
hudakz 0:acf75feb0947 371 // if 0 was picked then record its position in LastZero
hudakz 0:acf75feb0947 372 if (search_direction == 0)
hudakz 0:acf75feb0947 373 {
hudakz 0:acf75feb0947 374 last_zero = id_bit_number;
hudakz 0:acf75feb0947 375
hudakz 0:acf75feb0947 376 // check for Last discrepancy in family
hudakz 0:acf75feb0947 377 if (last_zero < 9)
hudakz 0:acf75feb0947 378 LastFamilyDiscrepancy = last_zero;
hudakz 0:acf75feb0947 379 }
hudakz 0:acf75feb0947 380 }
hudakz 0:acf75feb0947 381
hudakz 0:acf75feb0947 382 // set or clear the bit in the ROM byte rom_byte_number
hudakz 0:acf75feb0947 383 // with mask rom_byte_mask
hudakz 0:acf75feb0947 384 if (search_direction == 1)
hudakz 0:acf75feb0947 385 ROM_NO[rom_byte_number] |= rom_byte_mask;
hudakz 0:acf75feb0947 386 else
hudakz 0:acf75feb0947 387 ROM_NO[rom_byte_number] &= ~rom_byte_mask;
hudakz 0:acf75feb0947 388
hudakz 0:acf75feb0947 389 // serial number search direction write bit
hudakz 0:acf75feb0947 390 write_bit(search_direction);
hudakz 0:acf75feb0947 391
hudakz 0:acf75feb0947 392 // increment the byte counter id_bit_number
hudakz 0:acf75feb0947 393 // and shift the mask rom_byte_mask
hudakz 0:acf75feb0947 394 id_bit_number++;
hudakz 0:acf75feb0947 395 rom_byte_mask <<= 1;
hudakz 0:acf75feb0947 396
hudakz 0:acf75feb0947 397 // if the mask is 0 then go to new SerialNum byte rom_byte_number and reset mask
hudakz 0:acf75feb0947 398 if (rom_byte_mask == 0)
hudakz 0:acf75feb0947 399 {
hudakz 0:acf75feb0947 400 rom_byte_number++;
hudakz 0:acf75feb0947 401 rom_byte_mask = 1;
hudakz 0:acf75feb0947 402 }
hudakz 0:acf75feb0947 403 }
hudakz 0:acf75feb0947 404 }
hudakz 0:acf75feb0947 405 while(rom_byte_number < 8); // loop until through all ROM bytes 0-7
hudakz 0:acf75feb0947 406
hudakz 0:acf75feb0947 407 // if the search was successful then
hudakz 0:acf75feb0947 408 if (!(id_bit_number < 65))
hudakz 0:acf75feb0947 409 {
hudakz 0:acf75feb0947 410 // search successful so set LastDiscrepancy,LastDeviceFlag,search_result
hudakz 0:acf75feb0947 411 LastDiscrepancy = last_zero;
hudakz 0:acf75feb0947 412
hudakz 0:acf75feb0947 413 // check for last device
hudakz 0:acf75feb0947 414 if (LastDiscrepancy == 0)
hudakz 0:acf75feb0947 415 LastDeviceFlag = true;
hudakz 0:acf75feb0947 416
hudakz 0:acf75feb0947 417 search_result = true;
hudakz 0:acf75feb0947 418 }
hudakz 0:acf75feb0947 419 }
hudakz 0:acf75feb0947 420
hudakz 0:acf75feb0947 421 // if no device found then reset counters so next 'search' will be like a first
hudakz 0:acf75feb0947 422 if (!search_result || !ROM_NO[0])
hudakz 0:acf75feb0947 423 {
hudakz 0:acf75feb0947 424 LastDiscrepancy = 0;
hudakz 0:acf75feb0947 425 LastDeviceFlag = false;
hudakz 0:acf75feb0947 426 LastFamilyDiscrepancy = 0;
hudakz 0:acf75feb0947 427 search_result = false;
hudakz 0:acf75feb0947 428 }
hudakz 0:acf75feb0947 429 for (int i = 0; i < 8; i++) newAddr[i] = ROM_NO[i];
hudakz 0:acf75feb0947 430 return search_result;
hudakz 0:acf75feb0947 431 }
hudakz 0:acf75feb0947 432
hudakz 0:acf75feb0947 433 #endif
hudakz 0:acf75feb0947 434
hudakz 0:acf75feb0947 435 #if ONEWIRE_CRC
hudakz 0:acf75feb0947 436 // The 1-Wire CRC scheme is described in Maxim Application Note 27:
hudakz 0:acf75feb0947 437 // "Understanding and Using Cyclic Redundancy Checks with Maxim iButton Products"
hudakz 0:acf75feb0947 438 // Compute a Dallas Semiconductor 8 bit CRC directly.
hudakz 0:acf75feb0947 439 //
hudakz 0:acf75feb0947 440 uint8_t OneWire::crc8(const uint8_t *addr, uint8_t len)
hudakz 0:acf75feb0947 441 {
hudakz 0:acf75feb0947 442 uint8_t crc = 0;
hudakz 0:acf75feb0947 443
hudakz 0:acf75feb0947 444 while (len--) {
hudakz 0:acf75feb0947 445 uint8_t inbyte = *addr++;
hudakz 0:acf75feb0947 446 for (uint8_t i = 8; i; i--) {
hudakz 0:acf75feb0947 447 uint8_t mix = (crc ^ inbyte) & 0x01;
hudakz 0:acf75feb0947 448 crc >>= 1;
hudakz 0:acf75feb0947 449 if (mix) crc ^= 0x8C;
hudakz 0:acf75feb0947 450 inbyte >>= 1;
hudakz 0:acf75feb0947 451 }
hudakz 0:acf75feb0947 452 }
hudakz 0:acf75feb0947 453 return crc;
hudakz 0:acf75feb0947 454 }
hudakz 0:acf75feb0947 455 #endif
hudakz 6:d6e084297fb9 456