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@6:d2452e9b169b, 2015-10-05 (annotated)

Committer:
Bobty
Date:
Mon Oct 05 14:03:29 2015 +0000
Revision:
6:d2452e9b169b
Parent:
5:45b6a39002f1
Child:
7:0a87f8c2d9e6
Changed return code from search to be more meaningful about the reason for failure

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 {
Bobty 5:45b6a39002f1 15 __disable_irq();
simonbarker 0:d961f715d82b 16 bit = bit & 0x01;
Bobty 2:b7ee49dbd7ef 17 if (bit)
Bobty 2:b7ee49dbd7ef 18 {
simonbarker 0:d961f715d82b 19 // Write '1' bit
simonbarker 0:d961f715d82b 20 oneBus_.output();
simonbarker 0:d961f715d82b 21 oneBus_ = 0;
Bobty 5:45b6a39002f1 22 wait_us(12);
simonbarker 0:d961f715d82b 23 oneBus_.input();
simonbarker 0:d961f715d82b 24 wait_us(60);
Bobty 2:b7ee49dbd7ef 25 }
Bobty 2:b7ee49dbd7ef 26 else
Bobty 2:b7ee49dbd7ef 27 {
simonbarker 0:d961f715d82b 28 // Write '0' bit
simonbarker 0:d961f715d82b 29 oneBus_.output();
simonbarker 0:d961f715d82b 30 oneBus_ = 0;
Bobty 5:45b6a39002f1 31 wait_us(60);
simonbarker 0:d961f715d82b 32 oneBus_.input();
Bobty 5:45b6a39002f1 33 wait_us(12);
simonbarker 0:d961f715d82b 34 }
Bobty 5:45b6a39002f1 35 __enable_irq();
simonbarker 0:d961f715d82b 36 }
simonbarker 0:d961f715d82b 37
Bobty 2:b7ee49dbd7ef 38 int Onewire::readBit()
Bobty 2:b7ee49dbd7ef 39 {
simonbarker 0:d961f715d82b 40 char result;
simonbarker 0:d961f715d82b 41
Bobty 5:45b6a39002f1 42 __disable_irq();
simonbarker 0:d961f715d82b 43 oneBus_.output();
simonbarker 0:d961f715d82b 44 oneBus_ = 0;
Bobty 5:45b6a39002f1 45 wait_us(5);
simonbarker 0:d961f715d82b 46 oneBus_.input();
Bobty 5:45b6a39002f1 47 wait_us(7);
simonbarker 0:d961f715d82b 48 result = oneBus_.read();
Bobty 5:45b6a39002f1 49 wait_us(60);
Bobty 5:45b6a39002f1 50 __enable_irq();
simonbarker 0:d961f715d82b 51 return result;
simonbarker 0:d961f715d82b 52 }
simonbarker 0:d961f715d82b 53
Bobty 2:b7ee49dbd7ef 54 int Onewire::init()
Bobty 2:b7ee49dbd7ef 55 {
simonbarker 0:d961f715d82b 56 oneBus_.output();
simonbarker 0:d961f715d82b 57 oneBus_ = 0;
simonbarker 0:d961f715d82b 58 wait_us(480);
Bobty 5:45b6a39002f1 59 __disable_irq();
simonbarker 0:d961f715d82b 60 oneBus_.input();
simonbarker 0:d961f715d82b 61 wait_us(60);
Bobty 2:b7ee49dbd7ef 62 if (oneBus_.read() == 0)
Bobty 2:b7ee49dbd7ef 63 {
Bobty 5:45b6a39002f1 64 __enable_irq();
Bobty 5:45b6a39002f1 65 wait_us(100);
simonbarker 0:d961f715d82b 66 return 1;
simonbarker 0:d961f715d82b 67 }
Bobty 5:45b6a39002f1 68 __enable_irq();
simonbarker 0:d961f715d82b 69 return 0;
simonbarker 0:d961f715d82b 70 }
Bobty 2:b7ee49dbd7ef 71
Bobty 2:b7ee49dbd7ef 72 int Onewire::readByte()
Bobty 2:b7ee49dbd7ef 73 {
simonbarker 0:d961f715d82b 74 int result = 0;
simonbarker 0:d961f715d82b 75
Bobty 4:b678c7c8203c 76 for (int loop = 0; loop < ONEWIRE_ADDR_BYTES; loop++) {
simonbarker 0:d961f715d82b 77 // shift the result to get it ready for the next bit
simonbarker 0:d961f715d82b 78 result >>= 1;
simonbarker 0:d961f715d82b 79
simonbarker 0:d961f715d82b 80 // if result is one, then set MS bit
simonbarker 0:d961f715d82b 81 if (readBit())
simonbarker 0:d961f715d82b 82 result |= 0x80;
simonbarker 0:d961f715d82b 83 }
simonbarker 0:d961f715d82b 84 return result;
simonbarker 0:d961f715d82b 85 }
Bobty 2:b7ee49dbd7ef 86
Bobty 2:b7ee49dbd7ef 87 void Onewire::writeByte(char data)
Bobty 2:b7ee49dbd7ef 88 {
simonbarker 0:d961f715d82b 89 // Loop to write each bit in the byte, LS-bit first
Bobty 4:b678c7c8203c 90 for (int loop = 0; loop < ONEWIRE_ADDR_BYTES; loop++) {
simonbarker 0:d961f715d82b 91 writeBit(data & 0x01);
simonbarker 0:d961f715d82b 92
simonbarker 0:d961f715d82b 93 // shift the data byte for the next bit
simonbarker 0:d961f715d82b 94 data >>= 1;
simonbarker 0:d961f715d82b 95 }
simonbarker 0:d961f715d82b 96 }
Bobty 2:b7ee49dbd7ef 97
Bobty 2:b7ee49dbd7ef 98 unsigned char Onewire::CRC(unsigned char* addr, unsigned char len)
Bobty 2:b7ee49dbd7ef 99 {
simonbarker 0:d961f715d82b 100 unsigned char i, j;
simonbarker 0:d961f715d82b 101 unsigned char crc = 0;
simonbarker 0:d961f715d82b 102
simonbarker 0:d961f715d82b 103 for (i = 0; i < len; i++) {
simonbarker 0:d961f715d82b 104 unsigned char inbyte = addr[i];
Bobty 4:b678c7c8203c 105 for (j = 0; j < ONEWIRE_ADDR_BYTES; j++) {
simonbarker 0:d961f715d82b 106 unsigned char mix = (crc ^ inbyte) & 0x01;
simonbarker 0:d961f715d82b 107 crc >>= 1;
simonbarker 0:d961f715d82b 108 if (mix) crc ^= 0x8C;
simonbarker 0:d961f715d82b 109 inbyte >>= 1;
simonbarker 0:d961f715d82b 110 }
simonbarker 0:d961f715d82b 111 }
simonbarker 0:d961f715d82b 112 return crc;
simonbarker 0:d961f715d82b 113 }
simonbarker 0:d961f715d82b 114
Bobty 1:8e9464e05ddf 115 //
Bobty 1:8e9464e05ddf 116 // You need to use this function to start a search again from the beginning.
Bobty 1:8e9464e05ddf 117 // You do not need to do it for the first search, though you could.
Bobty 1:8e9464e05ddf 118 //
Bobty 1:8e9464e05ddf 119 void Onewire::reset_search()
Bobty 1:8e9464e05ddf 120 {
Bobty 2:b7ee49dbd7ef 121 // reset the search state
Bobty 2:b7ee49dbd7ef 122 _search_LastDiscrepancy = 0;
Bobty 2:b7ee49dbd7ef 123 _search_LastDeviceFlag = false;
Bobty 2:b7ee49dbd7ef 124 _search_LastFamilyDiscrepancy = 0;
Bobty 4:b678c7c8203c 125 for(int i = ONEWIRE_ADDR_BYTES-1; i >= 0; i--)
Bobty 2:b7ee49dbd7ef 126 _search_ROM_NO[i] = 0;
Bobty 1:8e9464e05ddf 127 }
Bobty 1:8e9464e05ddf 128
Bobty 2:b7ee49dbd7ef 129 // Search Copied from Arduino code
Bobty 1:8e9464e05ddf 130 //
Bobty 6:d2452e9b169b 131 // Perform a search.
Bobty 6:d2452e9b169b 132 // Returns
Bobty 6:d2452e9b169b 133 // ONEWIRE_OK if a new address has been returned.
Bobty 6:d2452e9b169b 134 // ONEWIRE_SEARCH_ALL_DONE = all devices found
Bobty 6:d2452e9b169b 135 // ONEWIRE_SEARCH_INIT_FAIL = failed to init
Bobty 6:d2452e9b169b 136 // ONEWIRE_SEARCH_NOT_FOUND = no devices found If this function returns a '1' then it has
Bobty 1:8e9464e05ddf 137 // enumerated the next device and you may retrieve the ROM from the
Bobty 1:8e9464e05ddf 138 // Onewire::address variable. If there are no devices, no further
Bobty 1:8e9464e05ddf 139 // devices, or something horrible happens in the middle of the
Bobty 1:8e9464e05ddf 140 // enumeration then a 0 is returned. If a new device is found then
Bobty 1:8e9464e05ddf 141 // its address is copied to newAddr. Use Onewire::reset_search() to
Bobty 1:8e9464e05ddf 142 // start over.
Bobty 1:8e9464e05ddf 143 //
Bobty 1:8e9464e05ddf 144 // --- Replaced by the one from the Dallas Semiconductor web site ---
Bobty 1:8e9464e05ddf 145 //--------------------------------------------------------------------------
Bobty 1:8e9464e05ddf 146 // Perform the 1-Wire Search Algorithm on the 1-Wire bus using the existing
Bobty 1:8e9464e05ddf 147 // search state.
Bobty 1:8e9464e05ddf 148 // Return TRUE : device found, ROM number in ROM_NO buffer
Bobty 1:8e9464e05ddf 149 // FALSE : device not found, end of search
Bobty 1:8e9464e05ddf 150 //
Bobty 1:8e9464e05ddf 151 uint8_t Onewire::search(uint8_t *newAddr)
Bobty 1:8e9464e05ddf 152 {
Bobty 2:b7ee49dbd7ef 153 uint8_t id_bit_number = 1;
Bobty 6:d2452e9b169b 154 uint8_t last_zero = 0, rom_byte_number = 0;
Bobty 6:d2452e9b169b 155 uint8_t search_result = ONEWIRE_SEARCH_ALL_DONE;
Bobty 2:b7ee49dbd7ef 156 uint8_t id_bit = 0, cmp_id_bit = 0;
Bobty 1:8e9464e05ddf 157
Bobty 1:8e9464e05ddf 158 // initialize for search
Bobty 2:b7ee49dbd7ef 159 unsigned char rom_byte_mask = 1, search_direction = 0;
Bobty 1:8e9464e05ddf 160
Bobty 1:8e9464e05ddf 161 // if the last call was not the last one
Bobty 1:8e9464e05ddf 162 if (!_search_LastDeviceFlag)
Bobty 1:8e9464e05ddf 163 {
Bobty 1:8e9464e05ddf 164 // 1-Wire reset
Bobty 1:8e9464e05ddf 165 if (!init())
Bobty 1:8e9464e05ddf 166 {
Bobty 1:8e9464e05ddf 167 // reset the search
Bobty 1:8e9464e05ddf 168 _search_LastDiscrepancy = 0;
Bobty 1:8e9464e05ddf 169 _search_LastDeviceFlag = false;
Bobty 1:8e9464e05ddf 170 _search_LastFamilyDiscrepancy = 0;
Bobty 6:d2452e9b169b 171 return ONEWIRE_SEARCH_INIT_FAIL;
Bobty 1:8e9464e05ddf 172 }
Bobty 1:8e9464e05ddf 173
Bobty 1:8e9464e05ddf 174 // issue the search command
Bobty 1:8e9464e05ddf 175 writeByte(0xF0);
Bobty 1:8e9464e05ddf 176
Bobty 1:8e9464e05ddf 177 // loop to do the search
Bobty 1:8e9464e05ddf 178 do
Bobty 1:8e9464e05ddf 179 {
Bobty 1:8e9464e05ddf 180 // read a bit and its complement
Bobty 1:8e9464e05ddf 181 id_bit = readBit();
Bobty 1:8e9464e05ddf 182 cmp_id_bit = readBit();
Bobty 1:8e9464e05ddf 183
Bobty 1:8e9464e05ddf 184 // check for no devices on 1-wire
Bobty 1:8e9464e05ddf 185 if ((id_bit == 1) && (cmp_id_bit == 1))
Bobty 1:8e9464e05ddf 186 break;
Bobty 1:8e9464e05ddf 187 else
Bobty 1:8e9464e05ddf 188 {
Bobty 1:8e9464e05ddf 189 // all devices coupled have 0 or 1
Bobty 1:8e9464e05ddf 190 if (id_bit != cmp_id_bit)
Bobty 1:8e9464e05ddf 191 search_direction = id_bit; // bit write value for search
Bobty 1:8e9464e05ddf 192 else
Bobty 1:8e9464e05ddf 193 {
Bobty 1:8e9464e05ddf 194 // if this discrepancy if before the Last Discrepancy
Bobty 1:8e9464e05ddf 195 // on a previous next then pick the same as last time
Bobty 1:8e9464e05ddf 196 if (id_bit_number < _search_LastDiscrepancy)
Bobty 1:8e9464e05ddf 197 search_direction = ((_search_ROM_NO[rom_byte_number] & rom_byte_mask) > 0);
Bobty 1:8e9464e05ddf 198 else
Bobty 1:8e9464e05ddf 199 // if equal to last pick 1, if not then pick 0
Bobty 1:8e9464e05ddf 200 search_direction = (id_bit_number == _search_LastDiscrepancy);
Bobty 1:8e9464e05ddf 201
Bobty 1:8e9464e05ddf 202 // if 0 was picked then record its position in LastZero
Bobty 1:8e9464e05ddf 203 if (search_direction == 0)
Bobty 1:8e9464e05ddf 204 {
Bobty 1:8e9464e05ddf 205 last_zero = id_bit_number;
Bobty 1:8e9464e05ddf 206
Bobty 1:8e9464e05ddf 207 // check for Last discrepancy in family
Bobty 1:8e9464e05ddf 208 if (last_zero < 9)
Bobty 1:8e9464e05ddf 209 _search_LastFamilyDiscrepancy = last_zero;
Bobty 1:8e9464e05ddf 210 }
Bobty 1:8e9464e05ddf 211 }
Bobty 1:8e9464e05ddf 212
Bobty 1:8e9464e05ddf 213 // set or clear the bit in the ROM byte rom_byte_number
Bobty 1:8e9464e05ddf 214 // with mask rom_byte_mask
Bobty 1:8e9464e05ddf 215 if (search_direction == 1)
Bobty 1:8e9464e05ddf 216 _search_ROM_NO[rom_byte_number] |= rom_byte_mask;
Bobty 1:8e9464e05ddf 217 else
Bobty 1:8e9464e05ddf 218 _search_ROM_NO[rom_byte_number] &= ~rom_byte_mask;
Bobty 1:8e9464e05ddf 219
Bobty 1:8e9464e05ddf 220 // serial number search direction write bit
Bobty 1:8e9464e05ddf 221 writeBit(search_direction);
Bobty 1:8e9464e05ddf 222
Bobty 1:8e9464e05ddf 223 // increment the byte counter id_bit_number
Bobty 1:8e9464e05ddf 224 // and shift the mask rom_byte_mask
Bobty 1:8e9464e05ddf 225 id_bit_number++;
Bobty 1:8e9464e05ddf 226 rom_byte_mask <<= 1;
Bobty 1:8e9464e05ddf 227
Bobty 1:8e9464e05ddf 228 // if the mask is 0 then go to new SerialNum byte rom_byte_number and reset mask
Bobty 1:8e9464e05ddf 229 if (rom_byte_mask == 0)
Bobty 1:8e9464e05ddf 230 {
Bobty 1:8e9464e05ddf 231 rom_byte_number++;
Bobty 1:8e9464e05ddf 232 rom_byte_mask = 1;
Bobty 1:8e9464e05ddf 233 }
Bobty 1:8e9464e05ddf 234 }
Bobty 1:8e9464e05ddf 235 }
Bobty 4:b678c7c8203c 236 while(rom_byte_number < ONEWIRE_ADDR_BYTES); // loop until through all ROM bytes 0-7
Bobty 1:8e9464e05ddf 237
Bobty 1:8e9464e05ddf 238 // if the search was successful then
Bobty 1:8e9464e05ddf 239 if (!(id_bit_number < 65))
Bobty 1:8e9464e05ddf 240 {
Bobty 1:8e9464e05ddf 241 // search successful so set LastDiscrepancy,LastDeviceFlag,search_result
Bobty 1:8e9464e05ddf 242 _search_LastDiscrepancy = last_zero;
Bobty 1:8e9464e05ddf 243
Bobty 1:8e9464e05ddf 244 // check for last device
Bobty 1:8e9464e05ddf 245 if (_search_LastDiscrepancy == 0)
Bobty 1:8e9464e05ddf 246 _search_LastDeviceFlag = true;
Bobty 1:8e9464e05ddf 247
Bobty 6:d2452e9b169b 248 search_result = ONEWIRE_OK;
Bobty 1:8e9464e05ddf 249 }
Bobty 1:8e9464e05ddf 250 }
Bobty 1:8e9464e05ddf 251
Bobty 1:8e9464e05ddf 252 // if no device found then reset counters so next 'search' will be like a first
Bobty 6:d2452e9b169b 253 if (!_search_ROM_NO[0])
Bobty 1:8e9464e05ddf 254 {
Bobty 1:8e9464e05ddf 255 _search_LastDiscrepancy = 0;
Bobty 1:8e9464e05ddf 256 _search_LastDeviceFlag = false;
Bobty 1:8e9464e05ddf 257 _search_LastFamilyDiscrepancy = 0;
Bobty 6:d2452e9b169b 258 search_result = ONEWIRE_SEARCH_NOT_FOUND;
Bobty 1:8e9464e05ddf 259 }
Bobty 6:d2452e9b169b 260 if (search_result != ONEWIRE_OK)
Bobty 6:d2452e9b169b 261 return search_result;
Bobty 4:b678c7c8203c 262 for (int i = 0; i < ONEWIRE_ADDR_BYTES; i++)
Bobty 1:8e9464e05ddf 263 newAddr[i] = _search_ROM_NO[i];
Bobty 1:8e9464e05ddf 264 return search_result;
Bobty 1:8e9464e05ddf 265 }
Bobty 1:8e9464e05ddf 266