Rob Dobson / Onewire

Library to communicate with Maxim OneWire protocol devices Modified timings and IRQ overrides

Dependents:   RdGasUseMonitor

Fork of Onewire by Simon Barker

Onewire.cpp@3:712bf8967b68, 2015-02-21 (annotated)

Committer:
Bobty
Date:
Sat Feb 21 17:54:33 2015 +0000
Revision:
3:712bf8967b68
Parent:
2:b7ee49dbd7ef
Child:
4:b678c7c8203c
Added comments about source of code

Who changed what in which revision?

UserRevisionLine numberNew contents of line
Bobty 3:712bf8967b68 1 // Code derived from a number of sources including:
Bobty 3:712bf8967b68 2 // simonbarker on MBED
Bobty 3:712bf8967b68 3 // The search code is a port of Jim Studt's Adruino One Wire lib
Bobty 3:712bf8967b68 4 // Can handle multiple devices per pin
Bobty 3:712bf8967b68 5 // Rob Dobson, 2015
Bobty 3:712bf8967b68 6
simonbarker 0:d961f715d82b 7 #include "Onewire.h"
simonbarker 0:d961f715d82b 8
Bobty 2:b7ee49dbd7ef 9 Onewire::Onewire(PinName oneBus):oneBus_(oneBus)
Bobty 2:b7ee49dbd7ef 10 {
simonbarker 0:d961f715d82b 11 }
Bobty 2:b7ee49dbd7ef 12
Bobty 2:b7ee49dbd7ef 13 void Onewire::writeBit(int bit)
Bobty 2:b7ee49dbd7ef 14 {
simonbarker 0:d961f715d82b 15 bit = bit & 0x01;
Bobty 2:b7ee49dbd7ef 16 if (bit)
Bobty 2:b7ee49dbd7ef 17 {
simonbarker 0:d961f715d82b 18 // Write '1' bit
simonbarker 0:d961f715d82b 19 oneBus_.output();
simonbarker 0:d961f715d82b 20 oneBus_ = 0;
simonbarker 0:d961f715d82b 21 wait_us(5);
simonbarker 0:d961f715d82b 22 oneBus_.input();
simonbarker 0:d961f715d82b 23 wait_us(60);
Bobty 2:b7ee49dbd7ef 24 }
Bobty 2:b7ee49dbd7ef 25 else
Bobty 2:b7ee49dbd7ef 26 {
simonbarker 0:d961f715d82b 27 // Write '0' bit
simonbarker 0:d961f715d82b 28 oneBus_.output();
simonbarker 0:d961f715d82b 29 oneBus_ = 0;
simonbarker 0:d961f715d82b 30 wait_us(70);
simonbarker 0:d961f715d82b 31 oneBus_.input();
simonbarker 0:d961f715d82b 32 wait_us(2);
simonbarker 0:d961f715d82b 33 }
simonbarker 0:d961f715d82b 34 }
simonbarker 0:d961f715d82b 35
Bobty 2:b7ee49dbd7ef 36 int Onewire::readBit()
Bobty 2:b7ee49dbd7ef 37 {
simonbarker 0:d961f715d82b 38 char result;
simonbarker 0:d961f715d82b 39
simonbarker 0:d961f715d82b 40 oneBus_.output();
simonbarker 0:d961f715d82b 41 oneBus_ = 0;
simonbarker 0:d961f715d82b 42 wait_us(1);
simonbarker 0:d961f715d82b 43 oneBus_.input();
simonbarker 0:d961f715d82b 44 wait_us(5);
simonbarker 0:d961f715d82b 45 result = oneBus_.read();
simonbarker 0:d961f715d82b 46 wait_us(55);
simonbarker 0:d961f715d82b 47 return result;
simonbarker 0:d961f715d82b 48 }
simonbarker 0:d961f715d82b 49
Bobty 2:b7ee49dbd7ef 50 int Onewire::init()
Bobty 2:b7ee49dbd7ef 51 {
simonbarker 0:d961f715d82b 52 oneBus_.output();
simonbarker 0:d961f715d82b 53 oneBus_ = 0;
simonbarker 0:d961f715d82b 54 wait_us(480);
simonbarker 0:d961f715d82b 55 oneBus_.input();
simonbarker 0:d961f715d82b 56 wait_us(60);
Bobty 2:b7ee49dbd7ef 57 if (oneBus_.read() == 0)
Bobty 2:b7ee49dbd7ef 58 {
simonbarker 0:d961f715d82b 59 wait(0.0001);
simonbarker 0:d961f715d82b 60 return 1;
simonbarker 0:d961f715d82b 61 }
simonbarker 0:d961f715d82b 62 return 0;
simonbarker 0:d961f715d82b 63 }
Bobty 2:b7ee49dbd7ef 64
Bobty 2:b7ee49dbd7ef 65 int Onewire::readByte()
Bobty 2:b7ee49dbd7ef 66 {
simonbarker 0:d961f715d82b 67 int result = 0;
simonbarker 0:d961f715d82b 68
simonbarker 0:d961f715d82b 69 for (int loop = 0; loop < 8; loop++) {
simonbarker 0:d961f715d82b 70 // shift the result to get it ready for the next bit
simonbarker 0:d961f715d82b 71 result >>= 1;
simonbarker 0:d961f715d82b 72
simonbarker 0:d961f715d82b 73 // if result is one, then set MS bit
simonbarker 0:d961f715d82b 74 if (readBit())
simonbarker 0:d961f715d82b 75 result |= 0x80;
simonbarker 0:d961f715d82b 76 }
simonbarker 0:d961f715d82b 77 return result;
simonbarker 0:d961f715d82b 78 }
Bobty 2:b7ee49dbd7ef 79
Bobty 2:b7ee49dbd7ef 80 void Onewire::writeByte(char data)
Bobty 2:b7ee49dbd7ef 81 {
simonbarker 0:d961f715d82b 82 // Loop to write each bit in the byte, LS-bit first
simonbarker 0:d961f715d82b 83 for (int loop = 0; loop < 8; loop++) {
simonbarker 0:d961f715d82b 84 writeBit(data & 0x01);
simonbarker 0:d961f715d82b 85
simonbarker 0:d961f715d82b 86 // shift the data byte for the next bit
simonbarker 0:d961f715d82b 87 data >>= 1;
simonbarker 0:d961f715d82b 88 }
simonbarker 0:d961f715d82b 89 }
Bobty 2:b7ee49dbd7ef 90
Bobty 2:b7ee49dbd7ef 91 unsigned char Onewire::CRC(unsigned char* addr, unsigned char len)
Bobty 2:b7ee49dbd7ef 92 {
simonbarker 0:d961f715d82b 93 unsigned char i, j;
simonbarker 0:d961f715d82b 94 unsigned char crc = 0;
simonbarker 0:d961f715d82b 95
simonbarker 0:d961f715d82b 96 for (i = 0; i < len; i++) {
simonbarker 0:d961f715d82b 97 unsigned char inbyte = addr[i];
simonbarker 0:d961f715d82b 98 for (j = 0; j < 8; j++) {
simonbarker 0:d961f715d82b 99 unsigned char mix = (crc ^ inbyte) & 0x01;
simonbarker 0:d961f715d82b 100 crc >>= 1;
simonbarker 0:d961f715d82b 101 if (mix) crc ^= 0x8C;
simonbarker 0:d961f715d82b 102 inbyte >>= 1;
simonbarker 0:d961f715d82b 103 }
simonbarker 0:d961f715d82b 104 }
simonbarker 0:d961f715d82b 105 return crc;
simonbarker 0:d961f715d82b 106 }
simonbarker 0:d961f715d82b 107
Bobty 1:8e9464e05ddf 108 //
Bobty 1:8e9464e05ddf 109 // You need to use this function to start a search again from the beginning.
Bobty 1:8e9464e05ddf 110 // You do not need to do it for the first search, though you could.
Bobty 1:8e9464e05ddf 111 //
Bobty 1:8e9464e05ddf 112 void Onewire::reset_search()
Bobty 1:8e9464e05ddf 113 {
Bobty 2:b7ee49dbd7ef 114 // reset the search state
Bobty 2:b7ee49dbd7ef 115 _search_LastDiscrepancy = 0;
Bobty 2:b7ee49dbd7ef 116 _search_LastDeviceFlag = false;
Bobty 2:b7ee49dbd7ef 117 _search_LastFamilyDiscrepancy = 0;
Bobty 2:b7ee49dbd7ef 118 for(int i = 7; i >= 0; i--)
Bobty 2:b7ee49dbd7ef 119 _search_ROM_NO[i] = 0;
Bobty 1:8e9464e05ddf 120 }
Bobty 1:8e9464e05ddf 121
Bobty 2:b7ee49dbd7ef 122 // Search Copied from Arduino code
Bobty 1:8e9464e05ddf 123 //
Bobty 1:8e9464e05ddf 124 // Perform a search. If this function returns a '1' then it has
Bobty 1:8e9464e05ddf 125 // enumerated the next device and you may retrieve the ROM from the
Bobty 1:8e9464e05ddf 126 // Onewire::address variable. If there are no devices, no further
Bobty 1:8e9464e05ddf 127 // devices, or something horrible happens in the middle of the
Bobty 1:8e9464e05ddf 128 // enumeration then a 0 is returned. If a new device is found then
Bobty 1:8e9464e05ddf 129 // its address is copied to newAddr. Use Onewire::reset_search() to
Bobty 1:8e9464e05ddf 130 // start over.
Bobty 1:8e9464e05ddf 131 //
Bobty 1:8e9464e05ddf 132 // --- Replaced by the one from the Dallas Semiconductor web site ---
Bobty 1:8e9464e05ddf 133 //--------------------------------------------------------------------------
Bobty 1:8e9464e05ddf 134 // Perform the 1-Wire Search Algorithm on the 1-Wire bus using the existing
Bobty 1:8e9464e05ddf 135 // search state.
Bobty 1:8e9464e05ddf 136 // Return TRUE : device found, ROM number in ROM_NO buffer
Bobty 1:8e9464e05ddf 137 // FALSE : device not found, end of search
Bobty 1:8e9464e05ddf 138 //
Bobty 1:8e9464e05ddf 139 uint8_t Onewire::search(uint8_t *newAddr)
Bobty 1:8e9464e05ddf 140 {
Bobty 2:b7ee49dbd7ef 141 uint8_t id_bit_number = 1;
Bobty 2:b7ee49dbd7ef 142 uint8_t last_zero = 0, rom_byte_number = 0, search_result = 0;
Bobty 2:b7ee49dbd7ef 143 uint8_t id_bit = 0, cmp_id_bit = 0;
Bobty 1:8e9464e05ddf 144
Bobty 1:8e9464e05ddf 145 // initialize for search
Bobty 2:b7ee49dbd7ef 146 unsigned char rom_byte_mask = 1, search_direction = 0;
Bobty 1:8e9464e05ddf 147
Bobty 1:8e9464e05ddf 148 // if the last call was not the last one
Bobty 1:8e9464e05ddf 149 if (!_search_LastDeviceFlag)
Bobty 1:8e9464e05ddf 150 {
Bobty 1:8e9464e05ddf 151 // 1-Wire reset
Bobty 1:8e9464e05ddf 152 if (!init())
Bobty 1:8e9464e05ddf 153 {
Bobty 1:8e9464e05ddf 154 // reset the search
Bobty 1:8e9464e05ddf 155 _search_LastDiscrepancy = 0;
Bobty 1:8e9464e05ddf 156 _search_LastDeviceFlag = false;
Bobty 1:8e9464e05ddf 157 _search_LastFamilyDiscrepancy = 0;
Bobty 1:8e9464e05ddf 158 return false;
Bobty 1:8e9464e05ddf 159 }
Bobty 1:8e9464e05ddf 160
Bobty 1:8e9464e05ddf 161 // issue the search command
Bobty 1:8e9464e05ddf 162 writeByte(0xF0);
Bobty 1:8e9464e05ddf 163
Bobty 1:8e9464e05ddf 164 // loop to do the search
Bobty 1:8e9464e05ddf 165 do
Bobty 1:8e9464e05ddf 166 {
Bobty 1:8e9464e05ddf 167 // read a bit and its complement
Bobty 1:8e9464e05ddf 168 id_bit = readBit();
Bobty 1:8e9464e05ddf 169 cmp_id_bit = readBit();
Bobty 1:8e9464e05ddf 170
Bobty 1:8e9464e05ddf 171 // check for no devices on 1-wire
Bobty 1:8e9464e05ddf 172 if ((id_bit == 1) && (cmp_id_bit == 1))
Bobty 1:8e9464e05ddf 173 break;
Bobty 1:8e9464e05ddf 174 else
Bobty 1:8e9464e05ddf 175 {
Bobty 1:8e9464e05ddf 176 // all devices coupled have 0 or 1
Bobty 1:8e9464e05ddf 177 if (id_bit != cmp_id_bit)
Bobty 1:8e9464e05ddf 178 search_direction = id_bit; // bit write value for search
Bobty 1:8e9464e05ddf 179 else
Bobty 1:8e9464e05ddf 180 {
Bobty 1:8e9464e05ddf 181 // if this discrepancy if before the Last Discrepancy
Bobty 1:8e9464e05ddf 182 // on a previous next then pick the same as last time
Bobty 1:8e9464e05ddf 183 if (id_bit_number < _search_LastDiscrepancy)
Bobty 1:8e9464e05ddf 184 search_direction = ((_search_ROM_NO[rom_byte_number] & rom_byte_mask) > 0);
Bobty 1:8e9464e05ddf 185 else
Bobty 1:8e9464e05ddf 186 // if equal to last pick 1, if not then pick 0
Bobty 1:8e9464e05ddf 187 search_direction = (id_bit_number == _search_LastDiscrepancy);
Bobty 1:8e9464e05ddf 188
Bobty 1:8e9464e05ddf 189 // if 0 was picked then record its position in LastZero
Bobty 1:8e9464e05ddf 190 if (search_direction == 0)
Bobty 1:8e9464e05ddf 191 {
Bobty 1:8e9464e05ddf 192 last_zero = id_bit_number;
Bobty 1:8e9464e05ddf 193
Bobty 1:8e9464e05ddf 194 // check for Last discrepancy in family
Bobty 1:8e9464e05ddf 195 if (last_zero < 9)
Bobty 1:8e9464e05ddf 196 _search_LastFamilyDiscrepancy = last_zero;
Bobty 1:8e9464e05ddf 197 }
Bobty 1:8e9464e05ddf 198 }
Bobty 1:8e9464e05ddf 199
Bobty 1:8e9464e05ddf 200 // set or clear the bit in the ROM byte rom_byte_number
Bobty 1:8e9464e05ddf 201 // with mask rom_byte_mask
Bobty 1:8e9464e05ddf 202 if (search_direction == 1)
Bobty 1:8e9464e05ddf 203 _search_ROM_NO[rom_byte_number] |= rom_byte_mask;
Bobty 1:8e9464e05ddf 204 else
Bobty 1:8e9464e05ddf 205 _search_ROM_NO[rom_byte_number] &= ~rom_byte_mask;
Bobty 1:8e9464e05ddf 206
Bobty 1:8e9464e05ddf 207 // serial number search direction write bit
Bobty 1:8e9464e05ddf 208 writeBit(search_direction);
Bobty 1:8e9464e05ddf 209
Bobty 1:8e9464e05ddf 210 // increment the byte counter id_bit_number
Bobty 1:8e9464e05ddf 211 // and shift the mask rom_byte_mask
Bobty 1:8e9464e05ddf 212 id_bit_number++;
Bobty 1:8e9464e05ddf 213 rom_byte_mask <<= 1;
Bobty 1:8e9464e05ddf 214
Bobty 1:8e9464e05ddf 215 // if the mask is 0 then go to new SerialNum byte rom_byte_number and reset mask
Bobty 1:8e9464e05ddf 216 if (rom_byte_mask == 0)
Bobty 1:8e9464e05ddf 217 {
Bobty 1:8e9464e05ddf 218 rom_byte_number++;
Bobty 1:8e9464e05ddf 219 rom_byte_mask = 1;
Bobty 1:8e9464e05ddf 220 }
Bobty 1:8e9464e05ddf 221 }
Bobty 1:8e9464e05ddf 222 }
Bobty 1:8e9464e05ddf 223 while(rom_byte_number < 8); // loop until through all ROM bytes 0-7
Bobty 1:8e9464e05ddf 224
Bobty 1:8e9464e05ddf 225 // if the search was successful then
Bobty 1:8e9464e05ddf 226 if (!(id_bit_number < 65))
Bobty 1:8e9464e05ddf 227 {
Bobty 1:8e9464e05ddf 228 // search successful so set LastDiscrepancy,LastDeviceFlag,search_result
Bobty 1:8e9464e05ddf 229 _search_LastDiscrepancy = last_zero;
Bobty 1:8e9464e05ddf 230
Bobty 1:8e9464e05ddf 231 // check for last device
Bobty 1:8e9464e05ddf 232 if (_search_LastDiscrepancy == 0)
Bobty 1:8e9464e05ddf 233 _search_LastDeviceFlag = true;
Bobty 1:8e9464e05ddf 234
Bobty 1:8e9464e05ddf 235 search_result = true;
Bobty 1:8e9464e05ddf 236 }
Bobty 1:8e9464e05ddf 237 }
Bobty 1:8e9464e05ddf 238
Bobty 1:8e9464e05ddf 239 // if no device found then reset counters so next 'search' will be like a first
Bobty 1:8e9464e05ddf 240 if (!search_result || !_search_ROM_NO[0])
Bobty 1:8e9464e05ddf 241 {
Bobty 1:8e9464e05ddf 242 _search_LastDiscrepancy = 0;
Bobty 1:8e9464e05ddf 243 _search_LastDeviceFlag = false;
Bobty 1:8e9464e05ddf 244 _search_LastFamilyDiscrepancy = 0;
Bobty 1:8e9464e05ddf 245 search_result = false;
Bobty 1:8e9464e05ddf 246 }
Bobty 1:8e9464e05ddf 247 for (int i = 0; i < 8; i++)
Bobty 1:8e9464e05ddf 248 newAddr[i] = _search_ROM_NO[i];
Bobty 1:8e9464e05ddf 249 return search_result;
Bobty 1:8e9464e05ddf 250 }
Bobty 1:8e9464e05ddf 251