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@5:45b6a39002f1, 2015-09-28 (annotated)

Committer:
Bobty
Date:
Mon Sep 28 10:31:58 2015 +0000
Revision:
5:45b6a39002f1
Parent:
4:b678c7c8203c
Child:
6:d2452e9b169b
Added IRQ handling code; Changed timings a little

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 1:8e9464e05ddf 131 // Perform a search. If this function returns a '1' then it has
Bobty 1:8e9464e05ddf 132 // enumerated the next device and you may retrieve the ROM from the
Bobty 1:8e9464e05ddf 133 // Onewire::address variable. If there are no devices, no further
Bobty 1:8e9464e05ddf 134 // devices, or something horrible happens in the middle of the
Bobty 1:8e9464e05ddf 135 // enumeration then a 0 is returned. If a new device is found then
Bobty 1:8e9464e05ddf 136 // its address is copied to newAddr. Use Onewire::reset_search() to
Bobty 1:8e9464e05ddf 137 // start over.
Bobty 1:8e9464e05ddf 138 //
Bobty 1:8e9464e05ddf 139 // --- Replaced by the one from the Dallas Semiconductor web site ---
Bobty 1:8e9464e05ddf 140 //--------------------------------------------------------------------------
Bobty 1:8e9464e05ddf 141 // Perform the 1-Wire Search Algorithm on the 1-Wire bus using the existing
Bobty 1:8e9464e05ddf 142 // search state.
Bobty 1:8e9464e05ddf 143 // Return TRUE : device found, ROM number in ROM_NO buffer
Bobty 1:8e9464e05ddf 144 // FALSE : device not found, end of search
Bobty 1:8e9464e05ddf 145 //
Bobty 1:8e9464e05ddf 146 uint8_t Onewire::search(uint8_t *newAddr)
Bobty 1:8e9464e05ddf 147 {
Bobty 2:b7ee49dbd7ef 148 uint8_t id_bit_number = 1;
Bobty 2:b7ee49dbd7ef 149 uint8_t last_zero = 0, rom_byte_number = 0, search_result = 0;
Bobty 2:b7ee49dbd7ef 150 uint8_t id_bit = 0, cmp_id_bit = 0;
Bobty 1:8e9464e05ddf 151
Bobty 1:8e9464e05ddf 152 // initialize for search
Bobty 2:b7ee49dbd7ef 153 unsigned char rom_byte_mask = 1, search_direction = 0;
Bobty 1:8e9464e05ddf 154
Bobty 1:8e9464e05ddf 155 // if the last call was not the last one
Bobty 1:8e9464e05ddf 156 if (!_search_LastDeviceFlag)
Bobty 1:8e9464e05ddf 157 {
Bobty 1:8e9464e05ddf 158 // 1-Wire reset
Bobty 1:8e9464e05ddf 159 if (!init())
Bobty 1:8e9464e05ddf 160 {
Bobty 1:8e9464e05ddf 161 // reset the search
Bobty 1:8e9464e05ddf 162 _search_LastDiscrepancy = 0;
Bobty 1:8e9464e05ddf 163 _search_LastDeviceFlag = false;
Bobty 1:8e9464e05ddf 164 _search_LastFamilyDiscrepancy = 0;
Bobty 1:8e9464e05ddf 165 return false;
Bobty 1:8e9464e05ddf 166 }
Bobty 1:8e9464e05ddf 167
Bobty 1:8e9464e05ddf 168 // issue the search command
Bobty 1:8e9464e05ddf 169 writeByte(0xF0);
Bobty 1:8e9464e05ddf 170
Bobty 1:8e9464e05ddf 171 // loop to do the search
Bobty 1:8e9464e05ddf 172 do
Bobty 1:8e9464e05ddf 173 {
Bobty 1:8e9464e05ddf 174 // read a bit and its complement
Bobty 1:8e9464e05ddf 175 id_bit = readBit();
Bobty 1:8e9464e05ddf 176 cmp_id_bit = readBit();
Bobty 1:8e9464e05ddf 177
Bobty 1:8e9464e05ddf 178 // check for no devices on 1-wire
Bobty 1:8e9464e05ddf 179 if ((id_bit == 1) && (cmp_id_bit == 1))
Bobty 1:8e9464e05ddf 180 break;
Bobty 1:8e9464e05ddf 181 else
Bobty 1:8e9464e05ddf 182 {
Bobty 1:8e9464e05ddf 183 // all devices coupled have 0 or 1
Bobty 1:8e9464e05ddf 184 if (id_bit != cmp_id_bit)
Bobty 1:8e9464e05ddf 185 search_direction = id_bit; // bit write value for search
Bobty 1:8e9464e05ddf 186 else
Bobty 1:8e9464e05ddf 187 {
Bobty 1:8e9464e05ddf 188 // if this discrepancy if before the Last Discrepancy
Bobty 1:8e9464e05ddf 189 // on a previous next then pick the same as last time
Bobty 1:8e9464e05ddf 190 if (id_bit_number < _search_LastDiscrepancy)
Bobty 1:8e9464e05ddf 191 search_direction = ((_search_ROM_NO[rom_byte_number] & rom_byte_mask) > 0);
Bobty 1:8e9464e05ddf 192 else
Bobty 1:8e9464e05ddf 193 // if equal to last pick 1, if not then pick 0
Bobty 1:8e9464e05ddf 194 search_direction = (id_bit_number == _search_LastDiscrepancy);
Bobty 1:8e9464e05ddf 195
Bobty 1:8e9464e05ddf 196 // if 0 was picked then record its position in LastZero
Bobty 1:8e9464e05ddf 197 if (search_direction == 0)
Bobty 1:8e9464e05ddf 198 {
Bobty 1:8e9464e05ddf 199 last_zero = id_bit_number;
Bobty 1:8e9464e05ddf 200
Bobty 1:8e9464e05ddf 201 // check for Last discrepancy in family
Bobty 1:8e9464e05ddf 202 if (last_zero < 9)
Bobty 1:8e9464e05ddf 203 _search_LastFamilyDiscrepancy = last_zero;
Bobty 1:8e9464e05ddf 204 }
Bobty 1:8e9464e05ddf 205 }
Bobty 1:8e9464e05ddf 206
Bobty 1:8e9464e05ddf 207 // set or clear the bit in the ROM byte rom_byte_number
Bobty 1:8e9464e05ddf 208 // with mask rom_byte_mask
Bobty 1:8e9464e05ddf 209 if (search_direction == 1)
Bobty 1:8e9464e05ddf 210 _search_ROM_NO[rom_byte_number] |= rom_byte_mask;
Bobty 1:8e9464e05ddf 211 else
Bobty 1:8e9464e05ddf 212 _search_ROM_NO[rom_byte_number] &= ~rom_byte_mask;
Bobty 1:8e9464e05ddf 213
Bobty 1:8e9464e05ddf 214 // serial number search direction write bit
Bobty 1:8e9464e05ddf 215 writeBit(search_direction);
Bobty 1:8e9464e05ddf 216
Bobty 1:8e9464e05ddf 217 // increment the byte counter id_bit_number
Bobty 1:8e9464e05ddf 218 // and shift the mask rom_byte_mask
Bobty 1:8e9464e05ddf 219 id_bit_number++;
Bobty 1:8e9464e05ddf 220 rom_byte_mask <<= 1;
Bobty 1:8e9464e05ddf 221
Bobty 1:8e9464e05ddf 222 // if the mask is 0 then go to new SerialNum byte rom_byte_number and reset mask
Bobty 1:8e9464e05ddf 223 if (rom_byte_mask == 0)
Bobty 1:8e9464e05ddf 224 {
Bobty 1:8e9464e05ddf 225 rom_byte_number++;
Bobty 1:8e9464e05ddf 226 rom_byte_mask = 1;
Bobty 1:8e9464e05ddf 227 }
Bobty 1:8e9464e05ddf 228 }
Bobty 1:8e9464e05ddf 229 }
Bobty 4:b678c7c8203c 230 while(rom_byte_number < ONEWIRE_ADDR_BYTES); // loop until through all ROM bytes 0-7
Bobty 1:8e9464e05ddf 231
Bobty 1:8e9464e05ddf 232 // if the search was successful then
Bobty 1:8e9464e05ddf 233 if (!(id_bit_number < 65))
Bobty 1:8e9464e05ddf 234 {
Bobty 1:8e9464e05ddf 235 // search successful so set LastDiscrepancy,LastDeviceFlag,search_result
Bobty 1:8e9464e05ddf 236 _search_LastDiscrepancy = last_zero;
Bobty 1:8e9464e05ddf 237
Bobty 1:8e9464e05ddf 238 // check for last device
Bobty 1:8e9464e05ddf 239 if (_search_LastDiscrepancy == 0)
Bobty 1:8e9464e05ddf 240 _search_LastDeviceFlag = true;
Bobty 1:8e9464e05ddf 241
Bobty 1:8e9464e05ddf 242 search_result = true;
Bobty 1:8e9464e05ddf 243 }
Bobty 1:8e9464e05ddf 244 }
Bobty 1:8e9464e05ddf 245
Bobty 1:8e9464e05ddf 246 // if no device found then reset counters so next 'search' will be like a first
Bobty 1:8e9464e05ddf 247 if (!search_result || !_search_ROM_NO[0])
Bobty 1:8e9464e05ddf 248 {
Bobty 1:8e9464e05ddf 249 _search_LastDiscrepancy = 0;
Bobty 1:8e9464e05ddf 250 _search_LastDeviceFlag = false;
Bobty 1:8e9464e05ddf 251 _search_LastFamilyDiscrepancy = 0;
Bobty 1:8e9464e05ddf 252 search_result = false;
Bobty 1:8e9464e05ddf 253 }
Bobty 4:b678c7c8203c 254 for (int i = 0; i < ONEWIRE_ADDR_BYTES; i++)
Bobty 1:8e9464e05ddf 255 newAddr[i] = _search_ROM_NO[i];
Bobty 1:8e9464e05ddf 256 return search_result;
Bobty 1:8e9464e05ddf 257 }
Bobty 1:8e9464e05ddf 258