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@2:b7ee49dbd7ef, 2015-02-21 (annotated)

Committer:
Bobty
Date:
Sat Feb 21 17:26:40 2015 +0000
Revision:
2:b7ee49dbd7ef
Parent:
1:8e9464e05ddf
Child:
3:712bf8967b68
Tidied up a little

Who changed what in which revision?

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