Zoltan Hudak / OneWire

Dallas' 1-Wire bus protocol library

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

OneWire.cpp@15:7f7759008807, 2020-07-20 (annotated)

Committer:
hudakz
Date:
Mon Jul 20 08:09:13 2020 +0000
Revision:
15:7f7759008807
Parent:
14:12b783661ff4
Child:
16:4c3edd30ad6e
Dallas' 1-Wire bus protocol library

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 9:4af0015b0f47 5 http://www.pjrc.com/teensy/td_libs_Onehtml
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 9:4af0015b0f47 10 contributors were interested in maintaining One 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 9:4af0015b0f47 38 http://www.pjrc.com/teensy/td_libs_Onehtml
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 #include "OneWire.h"
hudakz 0:acf75feb0947 117
hudakz 12:27a1b359b95c 118
hudakz 8:87fbdaba5535 119 /**
hudakz 10:c89b9ad6097c 120 * @brief Constructs a OneWire object.
hudakz 10:c89b9ad6097c 121 * @note GPIO is configured as output and an internal pull up resistor is connected.
hudakz 10:c89b9ad6097c 122 * But because for STM chips it takes very long time to change from output
hudakz 10:c89b9ad6097c 123 * to input an open drain mode is used rather and the GPIO remains output forever.
hudakz 8:87fbdaba5535 124 * @param
hudakz 8:87fbdaba5535 125 * @retval
hudakz 8:87fbdaba5535 126 */
hudakz 15:7f7759008807 127 OneWire::OneWire(PinName pin, int sample_point_us /* = 13 */) :
hudakz 15:7f7759008807 128 DigitalInOut(pin),
hudakz 15:7f7759008807 129 _sample_point_us(sample_point_us)
hudakz 7:acf3f0ee66d2 130 {
hudakz 15:7f7759008807 131 Timer timer;
hudakz 15:7f7759008807 132
hudakz 12:27a1b359b95c 133 MODE(); // set mode to either OpenDrain for STM or PullUp for others
hudakz 15:7f7759008807 134
hudakz 15:7f7759008807 135 // Measure bus transition time from ouput to input
hudakz 15:7f7759008807 136 timer.reset();
hudakz 15:7f7759008807 137 OUTPUT(); // set as output
hudakz 15:7f7759008807 138 WRITE(0); // pull the line down
hudakz 15:7f7759008807 139 timer.start();
hudakz 15:7f7759008807 140 INPUT(); // set as input (and release the bus)
hudakz 15:7f7759008807 141 timer.stop();
hudakz 15:7f7759008807 142 _out_to_in_transition_us = timer.read_us();
hudakz 15:7f7759008807 143
hudakz 15:7f7759008807 144 MBED_ASSERT(_out_to_in_transition_us < _sample_point_us);
hudakz 15:7f7759008807 145
hudakz 12:27a1b359b95c 146 INIT_WAIT;
hudakz 0:acf75feb0947 147 #if ONEWIRE_SEARCH
hudakz 0:acf75feb0947 148 reset_search();
hudakz 0:acf75feb0947 149 #endif
hudakz 0:acf75feb0947 150 }
hudakz 0:acf75feb0947 151
hudakz 10:c89b9ad6097c 152 /**
hudakz 10:c89b9ad6097c 153 * @brief Performs the onewire reset function.
hudakz 10:c89b9ad6097c 154 * @note We will wait up to 250uS for the bus to come high,
hudakz 10:c89b9ad6097c 155 * if it doesn't then it is broken or shorted and we return a 0;
hudakz 10:c89b9ad6097c 156 * @param
hudakz 10:c89b9ad6097c 157 * @retval 1 if a device asserted a presence pulse, 0 otherwise.
hudakz 10:c89b9ad6097c 158 */
hudakz 0:acf75feb0947 159 uint8_t OneWire::reset(void)
hudakz 0:acf75feb0947 160 {
hudakz 12:27a1b359b95c 161 uint8_t present;
hudakz 0:acf75feb0947 162
hudakz 9:4af0015b0f47 163 OUTPUT();
hudakz 12:27a1b359b95c 164 WRITE(0); // pull down the 1-wire bus do create reset pulse
hudakz 12:27a1b359b95c 165 WAIT_US(500); // wait at least 480 us
hudakz 12:27a1b359b95c 166 INPUT(); // release the 1-wire bus and go into receive mode
hudakz 12:27a1b359b95c 167 WAIT_US(90); // DS1820 waits about 15 to 60 us and generates a 60 to 240 us presence pulse
hudakz 12:27a1b359b95c 168 present = !READ(); // read the presence pulse
hudakz 12:27a1b359b95c 169 WAIT_US(420);
hudakz 12:27a1b359b95c 170
hudakz 12:27a1b359b95c 171 return present;
hudakz 0:acf75feb0947 172 }
hudakz 0:acf75feb0947 173
hudakz 10:c89b9ad6097c 174 /**
hudakz 10:c89b9ad6097c 175 * @brief Writes a bit.
hudakz 10:c89b9ad6097c 176 * @note GPIO registers are used for STM chips to cut time.
hudakz 10:c89b9ad6097c 177 * @param
hudakz 10:c89b9ad6097c 178 * @retval
hudakz 10:c89b9ad6097c 179 */
hudakz 0:acf75feb0947 180 void OneWire::write_bit(uint8_t v)
hudakz 0:acf75feb0947 181 {
hudakz 9:4af0015b0f47 182 OUTPUT();
hudakz 0:acf75feb0947 183 if (v & 1) {
hudakz 9:4af0015b0f47 184 WRITE(0); // drive output low
hudakz 12:27a1b359b95c 185 WAIT_US(1);
hudakz 9:4af0015b0f47 186 WRITE(1); // drive output high
hudakz 12:27a1b359b95c 187 WAIT_US(60);
hudakz 8:87fbdaba5535 188 }
hudakz 8:87fbdaba5535 189 else {
hudakz 9:4af0015b0f47 190 WRITE(0); // drive output low
hudakz 12:27a1b359b95c 191 WAIT_US(60);
hudakz 9:4af0015b0f47 192 WRITE(1); // drive output high
hudakz 12:27a1b359b95c 193 WAIT_US(1);
hudakz 0:acf75feb0947 194 }
hudakz 0:acf75feb0947 195 }
hudakz 0:acf75feb0947 196
hudakz 10:c89b9ad6097c 197 /**
hudakz 10:c89b9ad6097c 198 * @brief Reads a bit.
hudakz 10:c89b9ad6097c 199 * @note GPIO registers are used for STM chips to cut time.
hudakz 10:c89b9ad6097c 200 * @param
hudakz 10:c89b9ad6097c 201 * @retval
hudakz 10:c89b9ad6097c 202 */
hudakz 0:acf75feb0947 203 uint8_t OneWire::read_bit(void)
hudakz 0:acf75feb0947 204 {
hudakz 0:acf75feb0947 205 uint8_t r;
hudakz 0:acf75feb0947 206
hudakz 9:4af0015b0f47 207 OUTPUT();
hudakz 12:27a1b359b95c 208 WRITE(0);
hudakz 9:4af0015b0f47 209 INPUT();
hudakz 15:7f7759008807 210 wait_us(_sample_point_us - _out_to_in_transition_us); // wait till sample point
hudakz 9:4af0015b0f47 211 r = READ();
hudakz 14:12b783661ff4 212 WAIT_US(55);
hudakz 0:acf75feb0947 213 return r;
hudakz 0:acf75feb0947 214 }
hudakz 0:acf75feb0947 215
hudakz 10:c89b9ad6097c 216 /**
hudakz 10:c89b9ad6097c 217 * @brief Writes a byte.
hudakz 10:c89b9ad6097c 218 * @note The writing code uses the active drivers to raise the
hudakz 10:c89b9ad6097c 219 pin high, if you need power after the write (e.g. DS18S20 in
hudakz 10:c89b9ad6097c 220 parasite power mode) then set 'power' to 1, otherwise the pin will
hudakz 10:c89b9ad6097c 221 go tri-state at the end of the write to avoid heating in a short or
hudakz 10:c89b9ad6097c 222 other mishap.
hudakz 10:c89b9ad6097c 223 * @param
hudakz 10:c89b9ad6097c 224 * @retval
hudakz 10:c89b9ad6097c 225 */
hudakz 9:4af0015b0f47 226 void OneWire::write_byte(uint8_t v, uint8_t power /* = 0 */ )
hudakz 8:87fbdaba5535 227 {
hudakz 0:acf75feb0947 228 uint8_t bitMask;
hudakz 0:acf75feb0947 229
hudakz 9:4af0015b0f47 230 for (bitMask = 0x01; bitMask; bitMask <<= 1)
hudakz 9:4af0015b0f47 231 write_bit((bitMask & v) ? 1 : 0);
hudakz 8:87fbdaba5535 232 if (!power)
hudakz 9:4af0015b0f47 233 INPUT();
hudakz 0:acf75feb0947 234 }
hudakz 0:acf75feb0947 235
hudakz 8:87fbdaba5535 236 /**
hudakz 10:c89b9ad6097c 237 * @brief Writes bytes.
hudakz 8:87fbdaba5535 238 * @note
hudakz 8:87fbdaba5535 239 * @param
hudakz 8:87fbdaba5535 240 * @retval
hudakz 8:87fbdaba5535 241 */
hudakz 8:87fbdaba5535 242 void OneWire::write_bytes(const uint8_t* buf, uint16_t count, bool power /* = 0 */ )
hudakz 8:87fbdaba5535 243 {
hudakz 8:87fbdaba5535 244 for (uint16_t i = 0; i < count; i++)
hudakz 9:4af0015b0f47 245 write_byte(buf[i]);
hudakz 8:87fbdaba5535 246 if (!power)
hudakz 9:4af0015b0f47 247 INPUT();
hudakz 0:acf75feb0947 248 }
hudakz 0:acf75feb0947 249
hudakz 10:c89b9ad6097c 250 /**
hudakz 10:c89b9ad6097c 251 * @brief Reads a byte.
hudakz 10:c89b9ad6097c 252 * @note
hudakz 10:c89b9ad6097c 253 * @param
hudakz 10:c89b9ad6097c 254 * @retval
hudakz 10:c89b9ad6097c 255 */
hudakz 9:4af0015b0f47 256 uint8_t OneWire::read_byte()
hudakz 8:87fbdaba5535 257 {
hudakz 0:acf75feb0947 258 uint8_t bitMask;
hudakz 0:acf75feb0947 259 uint8_t r = 0;
hudakz 0:acf75feb0947 260
hudakz 0:acf75feb0947 261 for (bitMask = 0x01; bitMask; bitMask <<= 1) {
hudakz 9:4af0015b0f47 262 if (read_bit())
hudakz 8:87fbdaba5535 263 r |= bitMask;
hudakz 0:acf75feb0947 264 }
hudakz 8:87fbdaba5535 265
hudakz 0:acf75feb0947 266 return r;
hudakz 0:acf75feb0947 267 }
hudakz 0:acf75feb0947 268
hudakz 8:87fbdaba5535 269 /**
hudakz 10:c89b9ad6097c 270 * @brief Reads bytes.
hudakz 8:87fbdaba5535 271 * @note
hudakz 8:87fbdaba5535 272 * @param
hudakz 8:87fbdaba5535 273 * @retval
hudakz 8:87fbdaba5535 274 */
hudakz 8:87fbdaba5535 275 void OneWire::read_bytes(uint8_t* buf, uint16_t count)
hudakz 8:87fbdaba5535 276 {
hudakz 8:87fbdaba5535 277 for (uint16_t i = 0; i < count; i++)
hudakz 9:4af0015b0f47 278 buf[i] = read_byte();
hudakz 0:acf75feb0947 279 }
hudakz 0:acf75feb0947 280
hudakz 10:c89b9ad6097c 281 /**
hudakz 10:c89b9ad6097c 282 * @brief Selects ROM.
hudakz 10:c89b9ad6097c 283 * @note
hudakz 10:c89b9ad6097c 284 * @param
hudakz 10:c89b9ad6097c 285 * @retval
hudakz 10:c89b9ad6097c 286 */
hudakz 0:acf75feb0947 287 void OneWire::select(const uint8_t rom[8])
hudakz 0:acf75feb0947 288 {
hudakz 0:acf75feb0947 289 uint8_t i;
hudakz 0:acf75feb0947 290
hudakz 10:c89b9ad6097c 291 write_byte(0x55); // Choose ROM
hudakz 8:87fbdaba5535 292 for (i = 0; i < 8; i++)
hudakz 9:4af0015b0f47 293 write_byte(rom[i]);
hudakz 0:acf75feb0947 294 }
hudakz 0:acf75feb0947 295
hudakz 10:c89b9ad6097c 296 /**
hudakz 10:c89b9ad6097c 297 * @brief Skips ROM select.
hudakz 10:c89b9ad6097c 298 * @note
hudakz 10:c89b9ad6097c 299 * @param
hudakz 10:c89b9ad6097c 300 * @retval
hudakz 10:c89b9ad6097c 301 */
hudakz 0:acf75feb0947 302 void OneWire::skip()
hudakz 0:acf75feb0947 303 {
hudakz 10:c89b9ad6097c 304 write_byte(0xCC); // Skip ROM
hudakz 0:acf75feb0947 305 }
hudakz 0:acf75feb0947 306
hudakz 8:87fbdaba5535 307 /**
hudakz 10:c89b9ad6097c 308 * @brief Unpowers the chip.
hudakz 8:87fbdaba5535 309 * @note
hudakz 8:87fbdaba5535 310 * @param
hudakz 8:87fbdaba5535 311 * @retval
hudakz 8:87fbdaba5535 312 */
hudakz 0:acf75feb0947 313 void OneWire::depower()
hudakz 0:acf75feb0947 314 {
hudakz 9:4af0015b0f47 315 INPUT();
hudakz 0:acf75feb0947 316 }
hudakz 0:acf75feb0947 317
hudakz 0:acf75feb0947 318 #if ONEWIRE_SEARCH
hudakz 8:87fbdaba5535 319 //
hudakz 0:acf75feb0947 320
hudakz 10:c89b9ad6097c 321 /**
hudakz 10:c89b9ad6097c 322 * @brief Resets the search state.
hudakz 10:c89b9ad6097c 323 * @note We need to use this function to start a search again from the beginning.
hudakz 10:c89b9ad6097c 324 * We do not need to do it for the first search, though we could.
hudakz 10:c89b9ad6097c 325 * @param
hudakz 10:c89b9ad6097c 326 * @retval
hudakz 10:c89b9ad6097c 327 */
hudakz 0:acf75feb0947 328 void OneWire::reset_search()
hudakz 0:acf75feb0947 329 {
hudakz 8:87fbdaba5535 330 // reset the search state
hudakz 8:87fbdaba5535 331 LastDiscrepancy = 0;
hudakz 8:87fbdaba5535 332 LastDeviceFlag = false;
hudakz 8:87fbdaba5535 333 LastFamilyDiscrepancy = 0;
hudakz 8:87fbdaba5535 334 for (int i = 7;; i--) {
hudakz 8:87fbdaba5535 335 ROM_NO[i] = 0;
hudakz 8:87fbdaba5535 336 if (i == 0)
hudakz 8:87fbdaba5535 337 break;
hudakz 8:87fbdaba5535 338 }
hudakz 0:acf75feb0947 339 }
hudakz 0:acf75feb0947 340
hudakz 10:c89b9ad6097c 341 /**
hudakz 10:c89b9ad6097c 342 * @brief Sets the search state to find SearchFamily type devices.
hudakz 10:c89b9ad6097c 343 * @note
hudakz 10:c89b9ad6097c 344 * @param
hudakz 10:c89b9ad6097c 345 * @retval
hudakz 10:c89b9ad6097c 346 */
hudakz 0:acf75feb0947 347 void OneWire::target_search(uint8_t family_code)
hudakz 0:acf75feb0947 348 {
hudakz 8:87fbdaba5535 349 // set the search state to find SearchFamily type devices
hudakz 8:87fbdaba5535 350 ROM_NO[0] = family_code;
hudakz 8:87fbdaba5535 351 for (uint8_t i = 1; i < 8; i++)
hudakz 8:87fbdaba5535 352 ROM_NO[i] = 0;
hudakz 8:87fbdaba5535 353 LastDiscrepancy = 64;
hudakz 8:87fbdaba5535 354 LastFamilyDiscrepancy = 0;
hudakz 8:87fbdaba5535 355 LastDeviceFlag = false;
hudakz 0:acf75feb0947 356 }
hudakz 0:acf75feb0947 357
hudakz 10:c89b9ad6097c 358 /**
hudakz 10:c89b9ad6097c 359 * @brief Performs a search.
hudakz 10:c89b9ad6097c 360 * @note Perform a search. If this function returns a '1' then it has
hudakz 10:c89b9ad6097c 361 enumerated the next device and you may retrieve the ROM from the
hudakz 10:c89b9ad6097c 362 OneWire::address variable. If there are no devices, no further
hudakz 10:c89b9ad6097c 363 devices, or something horrible happens in the middle of the
hudakz 10:c89b9ad6097c 364 enumeration then a 0 is returned. If a new device is found then
hudakz 10:c89b9ad6097c 365 its address is copied to newAddr. Use OneWire::reset_search() to
hudakz 10:c89b9ad6097c 366 start over.
hudakz 10:c89b9ad6097c 367
hudakz 10:c89b9ad6097c 368 --- Replaced by the one from the Dallas Semiconductor web site ---
hudakz 10:c89b9ad6097c 369 -------------------------------------------------------------------------
hudakz 10:c89b9ad6097c 370 Perform the 1-Wire Search Algorithm on the 1-Wire bus using the existing
hudakz 10:c89b9ad6097c 371 search state.
hudakz 10:c89b9ad6097c 372 * @param
hudakz 10:c89b9ad6097c 373 * @retval true : device found, ROM number in ROM_NO buffer
hudakz 10:c89b9ad6097c 374 * false : device not found, end of search
hudakz 10:c89b9ad6097c 375 */
hudakz 8:87fbdaba5535 376 uint8_t OneWire::search(uint8_t* newAddr)
hudakz 0:acf75feb0947 377 {
hudakz 8:87fbdaba5535 378 uint8_t id_bit_number;
hudakz 8:87fbdaba5535 379 uint8_t last_zero, rom_byte_number, search_result;
hudakz 8:87fbdaba5535 380 uint8_t id_bit, cmp_id_bit;
hudakz 0:acf75feb0947 381
hudakz 8:87fbdaba5535 382 unsigned char rom_byte_mask, search_direction;
hudakz 0:acf75feb0947 383
hudakz 8:87fbdaba5535 384 // initialize for search
hudakz 8:87fbdaba5535 385 id_bit_number = 1;
hudakz 8:87fbdaba5535 386 last_zero = 0;
hudakz 8:87fbdaba5535 387 rom_byte_number = 0;
hudakz 8:87fbdaba5535 388 rom_byte_mask = 1;
hudakz 8:87fbdaba5535 389 search_result = 0;
hudakz 12:27a1b359b95c 390
hudakz 8:87fbdaba5535 391 // if the last call was not the last one
hudakz 8:87fbdaba5535 392 if (!LastDeviceFlag) {
hudakz 8:87fbdaba5535 393 // 1-Wire reset
hudakz 8:87fbdaba5535 394 if (!reset()) {
hudakz 8:87fbdaba5535 395 // reset the search
hudakz 8:87fbdaba5535 396 LastDiscrepancy = 0;
hudakz 8:87fbdaba5535 397 LastDeviceFlag = false;
hudakz 8:87fbdaba5535 398 LastFamilyDiscrepancy = 0;
hudakz 8:87fbdaba5535 399 return false;
hudakz 8:87fbdaba5535 400 }
hudakz 0:acf75feb0947 401
hudakz 8:87fbdaba5535 402 // issue the search command
hudakz 9:4af0015b0f47 403 write_byte(0xF0);
hudakz 0:acf75feb0947 404
hudakz 8:87fbdaba5535 405 // loop to do the search
hudakz 8:87fbdaba5535 406 do {
hudakz 8:87fbdaba5535 407 // read a bit and its complement
hudakz 8:87fbdaba5535 408 id_bit = read_bit();
hudakz 8:87fbdaba5535 409 cmp_id_bit = read_bit();
hudakz 0:acf75feb0947 410
hudakz 8:87fbdaba5535 411 // check for no devices on 1-wire
hudakz 8:87fbdaba5535 412 if ((id_bit == 1) && (cmp_id_bit == 1))
hudakz 8:87fbdaba5535 413 break;
hudakz 8:87fbdaba5535 414 else {
hudakz 8:87fbdaba5535 415 // all devices coupled have 0 or 1
hudakz 8:87fbdaba5535 416 if (id_bit != cmp_id_bit)
hudakz 8:87fbdaba5535 417 search_direction = id_bit; // bit write value for search
hudakz 8:87fbdaba5535 418 else {
hudakz 8:87fbdaba5535 419 // if this discrepancy if before the Last Discrepancy
hudakz 8:87fbdaba5535 420 // on a previous next then pick the same as last time
hudakz 8:87fbdaba5535 421 if (id_bit_number < LastDiscrepancy)
hudakz 8:87fbdaba5535 422 search_direction = ((ROM_NO[rom_byte_number] & rom_byte_mask) > 0);
hudakz 8:87fbdaba5535 423 else
hudakz 8:87fbdaba5535 424 // if equal to last pick 1, if not then pick 0
hudakz 8:87fbdaba5535 425 search_direction = (id_bit_number == LastDiscrepancy);
hudakz 0:acf75feb0947 426
hudakz 8:87fbdaba5535 427 // if 0 was picked then record its position in LastZero
hudakz 8:87fbdaba5535 428 if (search_direction == 0) {
hudakz 8:87fbdaba5535 429 last_zero = id_bit_number;
hudakz 0:acf75feb0947 430
hudakz 8:87fbdaba5535 431 // check for Last discrepancy in family
hudakz 8:87fbdaba5535 432 if (last_zero < 9)
hudakz 8:87fbdaba5535 433 LastFamilyDiscrepancy = last_zero;
hudakz 8:87fbdaba5535 434 }
hudakz 8:87fbdaba5535 435 }
hudakz 0:acf75feb0947 436
hudakz 8:87fbdaba5535 437 // set or clear the bit in the ROM byte rom_byte_number
hudakz 8:87fbdaba5535 438 // with mask rom_byte_mask
hudakz 8:87fbdaba5535 439 if (search_direction == 1)
hudakz 8:87fbdaba5535 440 ROM_NO[rom_byte_number] |= rom_byte_mask;
hudakz 8:87fbdaba5535 441 else
hudakz 8:87fbdaba5535 442 ROM_NO[rom_byte_number] &= ~rom_byte_mask;
hudakz 0:acf75feb0947 443
hudakz 8:87fbdaba5535 444 // serial number search direction write bit
hudakz 8:87fbdaba5535 445 write_bit(search_direction);
hudakz 0:acf75feb0947 446
hudakz 8:87fbdaba5535 447 // increment the byte counter id_bit_number
hudakz 8:87fbdaba5535 448 // and shift the mask rom_byte_mask
hudakz 8:87fbdaba5535 449 id_bit_number++;
hudakz 8:87fbdaba5535 450 rom_byte_mask <<= 1;
hudakz 0:acf75feb0947 451
hudakz 8:87fbdaba5535 452 // if the mask is 0 then go to new SerialNum byte rom_byte_number and reset mask
hudakz 8:87fbdaba5535 453 if (rom_byte_mask == 0) {
hudakz 8:87fbdaba5535 454 rom_byte_number++;
hudakz 8:87fbdaba5535 455 rom_byte_mask = 1;
hudakz 8:87fbdaba5535 456 }
hudakz 0:acf75feb0947 457 }
hudakz 8:87fbdaba5535 458 } while (rom_byte_number < 8);
hudakz 8:87fbdaba5535 459 // loop until through all ROM bytes 0-7
hudakz 8:87fbdaba5535 460 // if the search was successful then
hudakz 8:87fbdaba5535 461 if (!(id_bit_number < 65)) {
hudakz 8:87fbdaba5535 462 // search successful so set LastDiscrepancy,LastDeviceFlag,search_result
hudakz 8:87fbdaba5535 463 LastDiscrepancy = last_zero;
hudakz 0:acf75feb0947 464
hudakz 8:87fbdaba5535 465 // check for last device
hudakz 8:87fbdaba5535 466 if (LastDiscrepancy == 0)
hudakz 8:87fbdaba5535 467 LastDeviceFlag = true;
hudakz 0:acf75feb0947 468
hudakz 8:87fbdaba5535 469 search_result = true;
hudakz 8:87fbdaba5535 470 }
hudakz 8:87fbdaba5535 471 }
hudakz 0:acf75feb0947 472
hudakz 8:87fbdaba5535 473 // if no device found then reset counters so next 'search' will be like a first
hudakz 8:87fbdaba5535 474 if (!search_result || !ROM_NO[0]) {
hudakz 8:87fbdaba5535 475 LastDiscrepancy = 0;
hudakz 8:87fbdaba5535 476 LastDeviceFlag = false;
hudakz 8:87fbdaba5535 477 LastFamilyDiscrepancy = 0;
hudakz 8:87fbdaba5535 478 search_result = false;
hudakz 8:87fbdaba5535 479 }
hudakz 0:acf75feb0947 480
hudakz 8:87fbdaba5535 481 for (int i = 0; i < 8; i++)
hudakz 8:87fbdaba5535 482 newAddr[i] = ROM_NO[i];
hudakz 8:87fbdaba5535 483 return search_result;
hudakz 8:87fbdaba5535 484 }
hudakz 0:acf75feb0947 485 #endif
hudakz 10:c89b9ad6097c 486 //
hudakz 0:acf75feb0947 487 #if ONEWIRE_CRC
hudakz 0:acf75feb0947 488 //
hudakz 10:c89b9ad6097c 489 /**
hudakz 10:c89b9ad6097c 490 * @brief Computes a Dallas Semiconductor 8 bit CRC directly.
hudakz 10:c89b9ad6097c 491 * @note The 1-Wire CRC scheme is described in Maxim Application Note 27:
hudakz 10:c89b9ad6097c 492 "Understanding and Using Cyclic Redundancy Checks with Maxim iButton Products"
hudakz 10:c89b9ad6097c 493 * @param
hudakz 10:c89b9ad6097c 494 * @retval
hudakz 10:c89b9ad6097c 495 */
hudakz 8:87fbdaba5535 496 uint8_t OneWire::crc8(const uint8_t* addr, uint8_t len)
hudakz 0:acf75feb0947 497 {
hudakz 0:acf75feb0947 498 uint8_t crc = 0;
hudakz 8:87fbdaba5535 499
hudakz 0:acf75feb0947 500 while (len--) {
hudakz 0:acf75feb0947 501 uint8_t inbyte = *addr++;
hudakz 0:acf75feb0947 502 for (uint8_t i = 8; i; i--) {
hudakz 0:acf75feb0947 503 uint8_t mix = (crc ^ inbyte) & 0x01;
hudakz 0:acf75feb0947 504 crc >>= 1;
hudakz 8:87fbdaba5535 505 if (mix)
hudakz 8:87fbdaba5535 506 crc ^= 0x8C;
hudakz 0:acf75feb0947 507 inbyte >>= 1;
hudakz 0:acf75feb0947 508 }
hudakz 0:acf75feb0947 509 }
hudakz 8:87fbdaba5535 510
hudakz 0:acf75feb0947 511 return crc;
hudakz 0:acf75feb0947 512 }
hudakz 0:acf75feb0947 513 #endif