Thing Innovations / DS1820

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Fork of DS1820 by Erik -

DS1820.cpp@0:61d83318f2d6, 2010-12-19 (annotated)

Committer:
Michael_
Date:
Sun Dec 19 05:40:28 2010 +0000
Revision:
0:61d83318f2d6
Child:
1:6a427f54e82c
Dec 18, 2010 First pubication

Who changed what in which revision?

UserRevisionLine numberNew contents of line
Michael_ 0:61d83318f2d6 1 #include "DS1820.h"
Michael_ 0:61d83318f2d6 2 #include "mbed.h"
Michael_ 0:61d83318f2d6 3
Michael_ 0:61d83318f2d6 4 // Global variables shared between all DS1820 objects
Michael_ 0:61d83318f2d6 5 bool DS1820_done_flag;
Michael_ 0:61d83318f2d6 6 int DS1820_last_descrepancy;
Michael_ 0:61d83318f2d6 7 char DS1820_search_ROM[8];
Michael_ 0:61d83318f2d6 8
Michael_ 0:61d83318f2d6 9
Michael_ 0:61d83318f2d6 10 DS1820::DS1820 (PinName data_pin, PinName power_pin) : _datapin(data_pin), _parasitepin(power_pin) {
Michael_ 0:61d83318f2d6 11 int byte_counter;
Michael_ 0:61d83318f2d6 12 _parasite_power = true;
Michael_ 0:61d83318f2d6 13 for(byte_counter=0;byte_counter<8;byte_counter++)
Michael_ 0:61d83318f2d6 14 ROM[byte_counter] = 0xFF;
Michael_ 0:61d83318f2d6 15 for(byte_counter=0;byte_counter<9;byte_counter++)
Michael_ 0:61d83318f2d6 16 RAM[byte_counter] = 0x00;
Michael_ 0:61d83318f2d6 17 }
Michael_ 0:61d83318f2d6 18 DS1820::DS1820 (PinName data_pin) : _datapin(data_pin), _parasitepin(NC) {
Michael_ 0:61d83318f2d6 19 int byte_counter;
Michael_ 0:61d83318f2d6 20 _parasite_power = false;
Michael_ 0:61d83318f2d6 21 for(byte_counter=0;byte_counter<8;byte_counter++)
Michael_ 0:61d83318f2d6 22 ROM[byte_counter] = 0xFF;
Michael_ 0:61d83318f2d6 23 for(byte_counter=0;byte_counter<9;byte_counter++)
Michael_ 0:61d83318f2d6 24 RAM[byte_counter] = 0x00;
Michael_ 0:61d83318f2d6 25 }
Michael_ 0:61d83318f2d6 26
Michael_ 0:61d83318f2d6 27 bool DS1820::onewire_reset() {
Michael_ 0:61d83318f2d6 28 // This will return false if no devices are present on the data bus
Michael_ 0:61d83318f2d6 29 bool presence=false;
Michael_ 0:61d83318f2d6 30 _datapin.output();
Michael_ 0:61d83318f2d6 31 _datapin = 0; // bring low for 500 us
Michael_ 0:61d83318f2d6 32 wait_us(500);
Michael_ 0:61d83318f2d6 33 _datapin.input(); // let the data line float high
Michael_ 0:61d83318f2d6 34 wait_us(90); // wait 90us
Michael_ 0:61d83318f2d6 35 if (_datapin.read()==0) // see if any devices are pulling the data line low
Michael_ 0:61d83318f2d6 36 presence=true;
Michael_ 0:61d83318f2d6 37 wait_us(410);
Michael_ 0:61d83318f2d6 38 return presence;
Michael_ 0:61d83318f2d6 39 }
Michael_ 0:61d83318f2d6 40
Michael_ 0:61d83318f2d6 41 void DS1820::onewire_bit_out (bool bit_data) {
Michael_ 0:61d83318f2d6 42 _datapin.output();
Michael_ 0:61d83318f2d6 43 _datapin = 0;
Michael_ 0:61d83318f2d6 44 wait_us(5);
Michael_ 0:61d83318f2d6 45 if (bit_data) {
Michael_ 0:61d83318f2d6 46 _datapin.input(); // bring data line high
Michael_ 0:61d83318f2d6 47 wait_us(55);
Michael_ 0:61d83318f2d6 48 } else {
Michael_ 0:61d83318f2d6 49 wait_us(55); // keep data line low
Michael_ 0:61d83318f2d6 50 _datapin.input();
Michael_ 0:61d83318f2d6 51 }
Michael_ 0:61d83318f2d6 52 }
Michael_ 0:61d83318f2d6 53
Michael_ 0:61d83318f2d6 54 void DS1820::onewire_byte_out(char data) { // output data character (least sig bit first).
Michael_ 0:61d83318f2d6 55 int n;
Michael_ 0:61d83318f2d6 56 for (n=0; n<8; n++) {
Michael_ 0:61d83318f2d6 57 onewire_bit_out(data & 0x01);
Michael_ 0:61d83318f2d6 58 data = data >> 1; // now the next bit is in the least sig bit position.
Michael_ 0:61d83318f2d6 59 }
Michael_ 0:61d83318f2d6 60 }
Michael_ 0:61d83318f2d6 61
Michael_ 0:61d83318f2d6 62 bool DS1820::onewire_bit_in() {
Michael_ 0:61d83318f2d6 63 bool answer;
Michael_ 0:61d83318f2d6 64 _datapin.output();
Michael_ 0:61d83318f2d6 65 _datapin = 0;
Michael_ 0:61d83318f2d6 66 wait_us(5);
Michael_ 0:61d83318f2d6 67 _datapin.input();
Michael_ 0:61d83318f2d6 68 wait_us(5);
Michael_ 0:61d83318f2d6 69 answer = _datapin.read();
Michael_ 0:61d83318f2d6 70 wait_us(50);
Michael_ 0:61d83318f2d6 71 return answer;
Michael_ 0:61d83318f2d6 72 }
Michael_ 0:61d83318f2d6 73
Michael_ 0:61d83318f2d6 74 char DS1820::onewire_byte_in() { // read byte, least sig byte first
Michael_ 0:61d83318f2d6 75 char answer = 0x00;
Michael_ 0:61d83318f2d6 76 int i;
Michael_ 0:61d83318f2d6 77 for (i=0; i<8; i++) {
Michael_ 0:61d83318f2d6 78 answer = answer >> 1; // shift over to make room for the next bit
Michael_ 0:61d83318f2d6 79 if (onewire_bit_in())
Michael_ 0:61d83318f2d6 80 answer = answer | 0x80; // if the data port is high, make this bit a 1
Michael_ 0:61d83318f2d6 81 }
Michael_ 0:61d83318f2d6 82 return answer;
Michael_ 0:61d83318f2d6 83 }
Michael_ 0:61d83318f2d6 84
Michael_ 0:61d83318f2d6 85 bool DS1820::search_ROM() {
Michael_ 0:61d83318f2d6 86 return search_ROM_routine(0xF0); // Search ROM command
Michael_ 0:61d83318f2d6 87 }
Michael_ 0:61d83318f2d6 88
Michael_ 0:61d83318f2d6 89 bool DS1820::search_alarm() {
Michael_ 0:61d83318f2d6 90 return search_ROM_routine(0xEC); // Search Alarm command
Michael_ 0:61d83318f2d6 91 }
Michael_ 0:61d83318f2d6 92
Michael_ 0:61d83318f2d6 93 bool DS1820::search_ROM_routine(char command) {
Michael_ 0:61d83318f2d6 94 extern bool DS1820_done_flag;
Michael_ 0:61d83318f2d6 95 extern int DS1820_last_descrepancy;
Michael_ 0:61d83318f2d6 96 extern char DS1820_search_ROM[8];
Michael_ 0:61d83318f2d6 97 int descrepancy_marker, ROM_bit_index;
Michael_ 0:61d83318f2d6 98 bool return_value, Bit_A, Bit_B;
Michael_ 0:61d83318f2d6 99 char byte_counter, bit_mask;
Michael_ 0:61d83318f2d6 100
Michael_ 0:61d83318f2d6 101 return_value=false;
Michael_ 0:61d83318f2d6 102 if (!DS1820_done_flag) {
Michael_ 0:61d83318f2d6 103 if (!onewire_reset()) {
Michael_ 0:61d83318f2d6 104 DS1820_last_descrepancy = 0; // no devices present
Michael_ 0:61d83318f2d6 105 } else {
Michael_ 0:61d83318f2d6 106 ROM_bit_index=1;
Michael_ 0:61d83318f2d6 107 descrepancy_marker=0;
Michael_ 0:61d83318f2d6 108 onewire_byte_out(command); // Search ROM command or Search Alarm command
Michael_ 0:61d83318f2d6 109 byte_counter = 0;
Michael_ 0:61d83318f2d6 110 bit_mask = 0x01;
Michael_ 0:61d83318f2d6 111 while (ROM_bit_index<=64) {
Michael_ 0:61d83318f2d6 112 Bit_A = onewire_bit_in();
Michael_ 0:61d83318f2d6 113 Bit_B = onewire_bit_in();
Michael_ 0:61d83318f2d6 114 if (Bit_A & Bit_B) {
Michael_ 0:61d83318f2d6 115 descrepancy_marker = 0; // data read error, this should never happen
Michael_ 0:61d83318f2d6 116 ROM_bit_index = 0xFF;
Michael_ 0:61d83318f2d6 117 } else {
Michael_ 0:61d83318f2d6 118 if (Bit_A | Bit_B) {
Michael_ 0:61d83318f2d6 119 // Set ROM bit to Bit_A
Michael_ 0:61d83318f2d6 120 if (Bit_A) {
Michael_ 0:61d83318f2d6 121 DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] | bit_mask; // Set ROM bit to one
Michael_ 0:61d83318f2d6 122 } else {
Michael_ 0:61d83318f2d6 123 DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] & ~bit_mask; // Set ROM bit to zero
Michael_ 0:61d83318f2d6 124 }
Michael_ 0:61d83318f2d6 125 } else {
Michael_ 0:61d83318f2d6 126 // both bits A and B are low, so there are two or more devices present
Michael_ 0:61d83318f2d6 127 if ( ROM_bit_index == DS1820_last_descrepancy ) {
Michael_ 0:61d83318f2d6 128 DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] | bit_mask; // Set ROM bit to one
Michael_ 0:61d83318f2d6 129 } else {
Michael_ 0:61d83318f2d6 130 if ( ROM_bit_index > DS1820_last_descrepancy ) {
Michael_ 0:61d83318f2d6 131 DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] & ~bit_mask; // Set ROM bit to zero
Michael_ 0:61d83318f2d6 132 descrepancy_marker = ROM_bit_index;
Michael_ 0:61d83318f2d6 133 } else {
Michael_ 0:61d83318f2d6 134 if (( DS1820_search_ROM[byte_counter] & bit_mask) == 0x00 )
Michael_ 0:61d83318f2d6 135 descrepancy_marker = ROM_bit_index;
Michael_ 0:61d83318f2d6 136 }
Michael_ 0:61d83318f2d6 137 }
Michael_ 0:61d83318f2d6 138 }
Michael_ 0:61d83318f2d6 139 onewire_bit_out (DS1820_search_ROM[byte_counter] & bit_mask);
Michael_ 0:61d83318f2d6 140 ROM_bit_index++;
Michael_ 0:61d83318f2d6 141 if (bit_mask & 0x80) {
Michael_ 0:61d83318f2d6 142 byte_counter++;
Michael_ 0:61d83318f2d6 143 bit_mask = 0x01;
Michael_ 0:61d83318f2d6 144 } else {
Michael_ 0:61d83318f2d6 145 bit_mask = bit_mask << 1;
Michael_ 0:61d83318f2d6 146 }
Michael_ 0:61d83318f2d6 147 }
Michael_ 0:61d83318f2d6 148 }
Michael_ 0:61d83318f2d6 149 DS1820_last_descrepancy = descrepancy_marker;
Michael_ 0:61d83318f2d6 150 if (ROM_bit_index != 0xFF) {
Michael_ 0:61d83318f2d6 151 for(byte_counter=0;byte_counter<8;byte_counter++)
Michael_ 0:61d83318f2d6 152 ROM[byte_counter] = DS1820_search_ROM[byte_counter];
Michael_ 0:61d83318f2d6 153 return_value = true;
Michael_ 0:61d83318f2d6 154 }
Michael_ 0:61d83318f2d6 155 }
Michael_ 0:61d83318f2d6 156 if (DS1820_last_descrepancy == 0)
Michael_ 0:61d83318f2d6 157 DS1820_done_flag = true;
Michael_ 0:61d83318f2d6 158 }
Michael_ 0:61d83318f2d6 159 return return_value;
Michael_ 0:61d83318f2d6 160 }
Michael_ 0:61d83318f2d6 161
Michael_ 0:61d83318f2d6 162 void DS1820::search_ROM_setup() {
Michael_ 0:61d83318f2d6 163 extern bool DS1820_done_flag;
Michael_ 0:61d83318f2d6 164 extern int DS1820_last_descrepancy;
Michael_ 0:61d83318f2d6 165 extern char DS1820_search_ROM[8];
Michael_ 0:61d83318f2d6 166 DS1820_done_flag = false;
Michael_ 0:61d83318f2d6 167 DS1820_last_descrepancy = 0;
Michael_ 0:61d83318f2d6 168 int i;
Michael_ 0:61d83318f2d6 169 for (i=0; i<8; i++)
Michael_ 0:61d83318f2d6 170 DS1820_search_ROM[i]=0x00;
Michael_ 0:61d83318f2d6 171 }
Michael_ 0:61d83318f2d6 172
Michael_ 0:61d83318f2d6 173 void DS1820::read_ROM() {
Michael_ 0:61d83318f2d6 174 // NOTE: This command can only be used when there is one DS1820 on the bus. If this command
Michael_ 0:61d83318f2d6 175 // is used when there is more than one slave present on the bus, a data collision will occur
Michael_ 0:61d83318f2d6 176 // when all the DS1820s attempt to respond at the same time.
Michael_ 0:61d83318f2d6 177 int i;
Michael_ 0:61d83318f2d6 178 onewire_reset();
Michael_ 0:61d83318f2d6 179 onewire_byte_out(0x33); // Read ROM id
Michael_ 0:61d83318f2d6 180 for (i=0; i<8; i++)
Michael_ 0:61d83318f2d6 181 ROM[i]=onewire_byte_in();
Michael_ 0:61d83318f2d6 182 }
Michael_ 0:61d83318f2d6 183
Michael_ 0:61d83318f2d6 184 void DS1820::match_ROM() {
Michael_ 0:61d83318f2d6 185 // Used to select a specific device
Michael_ 0:61d83318f2d6 186 int i;
Michael_ 0:61d83318f2d6 187 onewire_reset();
Michael_ 0:61d83318f2d6 188 onewire_byte_out( 0x55); //Match ROM command
Michael_ 0:61d83318f2d6 189 for (i=0;i<8;i++)
Michael_ 0:61d83318f2d6 190 onewire_byte_out(ROM[i]);
Michael_ 0:61d83318f2d6 191 }
Michael_ 0:61d83318f2d6 192
Michael_ 0:61d83318f2d6 193 void DS1820::skip_ROM() {
Michael_ 0:61d83318f2d6 194 onewire_reset();
Michael_ 0:61d83318f2d6 195 onewire_byte_out(0xCC); // Skip ROM command
Michael_ 0:61d83318f2d6 196 }
Michael_ 0:61d83318f2d6 197
Michael_ 0:61d83318f2d6 198 bool DS1820::ROM_checksum_error() {
Michael_ 0:61d83318f2d6 199 char CRC=0x00;
Michael_ 0:61d83318f2d6 200 int i;
Michael_ 0:61d83318f2d6 201 for(i=0;i<7;i++) // Only going to shift the lower 7 bytes
Michael_ 0:61d83318f2d6 202 CRC = CRC_byte(CRC, ROM[i]);
Michael_ 0:61d83318f2d6 203 // After 7 bytes CRC should equal the 8th byte (ROM CRC)
Michael_ 0:61d83318f2d6 204 return (CRC!=ROM[7]); // will return true if there is a CRC checksum error
Michael_ 0:61d83318f2d6 205 }
Michael_ 0:61d83318f2d6 206
Michael_ 0:61d83318f2d6 207 bool DS1820::RAM_checksum_error() {
Michael_ 0:61d83318f2d6 208 char CRC=0x00;
Michael_ 0:61d83318f2d6 209 int i;
Michael_ 0:61d83318f2d6 210 read_RAM();
Michael_ 0:61d83318f2d6 211 for(i=0;i<8;i++) // Only going to shift the lower 8 bytes
Michael_ 0:61d83318f2d6 212 CRC = CRC_byte(CRC, RAM[i]);
Michael_ 0:61d83318f2d6 213 // After 8 bytes CRC should equal the 9th byte (RAM CRC)
Michael_ 0:61d83318f2d6 214 return (CRC!=RAM[8]); // will return true if there is a CRC checksum error
Michael_ 0:61d83318f2d6 215 }
Michael_ 0:61d83318f2d6 216
Michael_ 0:61d83318f2d6 217 char DS1820::CRC_byte (char CRC, char byte ) {
Michael_ 0:61d83318f2d6 218 int j;
Michael_ 0:61d83318f2d6 219 for(j=0;j<8;j++) {
Michael_ 0:61d83318f2d6 220 if ((byte & 0x01 ) ^ (CRC & 0x01)) {
Michael_ 0:61d83318f2d6 221 // DATA ^ LSB CRC = 1
Michael_ 0:61d83318f2d6 222 CRC = CRC>>1;
Michael_ 0:61d83318f2d6 223 // Set the MSB to 1
Michael_ 0:61d83318f2d6 224 CRC = CRC | 0x80;
Michael_ 0:61d83318f2d6 225 // Check bit 3
Michael_ 0:61d83318f2d6 226 if (CRC & 0x04) {
Michael_ 0:61d83318f2d6 227 CRC = CRC & 0xFB; // Bit 3 is set, so clear it
Michael_ 0:61d83318f2d6 228 } else {
Michael_ 0:61d83318f2d6 229 CRC = CRC | 0x04; // Bit 3 is clear, so set it
Michael_ 0:61d83318f2d6 230 }
Michael_ 0:61d83318f2d6 231 // Check bit 4
Michael_ 0:61d83318f2d6 232 if (CRC & 0x08) {
Michael_ 0:61d83318f2d6 233 CRC = CRC & 0xF7; // Bit 4 is set, so clear it
Michael_ 0:61d83318f2d6 234 } else {
Michael_ 0:61d83318f2d6 235 CRC = CRC | 0x08; // Bit 4 is clear, so set it
Michael_ 0:61d83318f2d6 236 }
Michael_ 0:61d83318f2d6 237 } else {
Michael_ 0:61d83318f2d6 238 // DATA ^ LSB CRC = 0
Michael_ 0:61d83318f2d6 239 CRC = CRC>>1;
Michael_ 0:61d83318f2d6 240 // clear MSB
Michael_ 0:61d83318f2d6 241 CRC = CRC & 0x7F;
Michael_ 0:61d83318f2d6 242 // No need to check bits, with DATA ^ LSB CRC = 0, they will remain unchanged
Michael_ 0:61d83318f2d6 243 }
Michael_ 0:61d83318f2d6 244 byte = byte>>1;
Michael_ 0:61d83318f2d6 245 }
Michael_ 0:61d83318f2d6 246 return CRC;
Michael_ 0:61d83318f2d6 247 }
Michael_ 0:61d83318f2d6 248
Michael_ 0:61d83318f2d6 249 void DS1820::convert_temperature(devices device) {
Michael_ 0:61d83318f2d6 250 // Convert temperature into scratchpad RAM for all devices at once
Michael_ 0:61d83318f2d6 251 if (device==all_devices)
Michael_ 0:61d83318f2d6 252 skip_ROM(); // Skip ROM command, will convert for ALL devices
Michael_ 0:61d83318f2d6 253 else
Michael_ 0:61d83318f2d6 254 match_ROM();
Michael_ 0:61d83318f2d6 255 onewire_byte_out( 0x44); // perform temperature conversion
Michael_ 0:61d83318f2d6 256 if (_parasite_power)
Michael_ 0:61d83318f2d6 257 _parasitepin = 1; // Parasite power strong pullup
Michael_ 0:61d83318f2d6 258 wait_ms(750);
Michael_ 0:61d83318f2d6 259 if (_parasite_power)
Michael_ 0:61d83318f2d6 260 _parasitepin = 0;
Michael_ 0:61d83318f2d6 261 }
Michael_ 0:61d83318f2d6 262
Michael_ 0:61d83318f2d6 263 void DS1820::read_RAM() {
Michael_ 0:61d83318f2d6 264 // This will copy the DS1820's 9 bytes of RAM data
Michael_ 0:61d83318f2d6 265 // into the objects RAM array. Functions that use
Michael_ 0:61d83318f2d6 266 // RAM values will automaticly call this procedure.
Michael_ 0:61d83318f2d6 267 int i;
Michael_ 0:61d83318f2d6 268 match_ROM(); // Select this device
Michael_ 0:61d83318f2d6 269 onewire_byte_out( 0xBE); //Read Scratchpad command
Michael_ 0:61d83318f2d6 270 for(i=0;i<9;i++) {
Michael_ 0:61d83318f2d6 271 RAM[i] = onewire_byte_in();
Michael_ 0:61d83318f2d6 272 }
Michael_ 0:61d83318f2d6 273 }
Michael_ 0:61d83318f2d6 274
Michael_ 0:61d83318f2d6 275 int DS1820::read_scratchpad() {
Michael_ 0:61d83318f2d6 276 int answer;
Michael_ 0:61d83318f2d6 277 read_RAM();
Michael_ 0:61d83318f2d6 278 answer = (RAM[2]<<8) + RAM[3];
Michael_ 0:61d83318f2d6 279 return answer;
Michael_ 0:61d83318f2d6 280 }
Michael_ 0:61d83318f2d6 281
Michael_ 0:61d83318f2d6 282 void DS1820::write_scratchpad(int data) {
Michael_ 0:61d83318f2d6 283 RAM[3] = data;
Michael_ 0:61d83318f2d6 284 RAM[2] = data>>8;
Michael_ 0:61d83318f2d6 285 match_ROM();
Michael_ 0:61d83318f2d6 286 onewire_byte_out(0x4E); // Copy scratchpad into DS1820 ram memory
Michael_ 0:61d83318f2d6 287 onewire_byte_out(RAM[2]); // T(H)
Michael_ 0:61d83318f2d6 288 onewire_byte_out(RAM[3]); // T(L)
Michael_ 0:61d83318f2d6 289 }
Michael_ 0:61d83318f2d6 290
Michael_ 0:61d83318f2d6 291 void DS1820::store_scratchpad(devices device) {
Michael_ 0:61d83318f2d6 292 if (device==all_devices)
Michael_ 0:61d83318f2d6 293 skip_ROM(); // Skip ROM command, will store for ALL devices
Michael_ 0:61d83318f2d6 294 else
Michael_ 0:61d83318f2d6 295 match_ROM();
Michael_ 0:61d83318f2d6 296 onewire_byte_out(0x48); // Write scratchpad into E2 command
Michael_ 0:61d83318f2d6 297 if (_parasite_power)
Michael_ 0:61d83318f2d6 298 _parasitepin=1;
Michael_ 0:61d83318f2d6 299 wait_ms(10); // Parasite power strong pullup for 10ms
Michael_ 0:61d83318f2d6 300 if (_parasite_power)
Michael_ 0:61d83318f2d6 301 _parasitepin=0;
Michael_ 0:61d83318f2d6 302 }
Michael_ 0:61d83318f2d6 303
Michael_ 0:61d83318f2d6 304 int DS1820::recall_scratchpad(devices device) {
Michael_ 0:61d83318f2d6 305 // This copies the E2 values into the DS1820's memory.
Michael_ 0:61d83318f2d6 306 // If you specify all_devices this will return zero, otherwise
Michael_ 0:61d83318f2d6 307 // it will return the value of the scratchpad memory.
Michael_ 0:61d83318f2d6 308 int answer=0;
Michael_ 0:61d83318f2d6 309 if (device==all_devices)
Michael_ 0:61d83318f2d6 310 skip_ROM(); // Skip ROM command, will recall for ALL devices
Michael_ 0:61d83318f2d6 311 else
Michael_ 0:61d83318f2d6 312 match_ROM();
Michael_ 0:61d83318f2d6 313 onewire_byte_out(0xB8); // Recall E2 data to scratchpad command
Michael_ 0:61d83318f2d6 314 wait_ms(10); // not sure I like polling for completion
Michael_ 0:61d83318f2d6 315 // it could cause an infinite loop
Michael_ 0:61d83318f2d6 316 if (device==DS1820::this_device) {
Michael_ 0:61d83318f2d6 317 read_RAM();
Michael_ 0:61d83318f2d6 318 answer = read_scratchpad();
Michael_ 0:61d83318f2d6 319 }
Michael_ 0:61d83318f2d6 320 return answer;
Michael_ 0:61d83318f2d6 321 }
Michael_ 0:61d83318f2d6 322
Michael_ 0:61d83318f2d6 323 float DS1820::temperature(char scale) {
Michael_ 0:61d83318f2d6 324 // The data specs state that count_per_degree should be 0x10 (16), I found my devices
Michael_ 0:61d83318f2d6 325 // to have a count_per_degree of 0x4B (75). With the standard resolution of 1/2 deg C
Michael_ 0:61d83318f2d6 326 // this allowed an expanded resolution of 1/150th of a deg C. I wouldn't rely on this
Michael_ 0:61d83318f2d6 327 // being super acurate, but it does allow for a smooth display in the 1/10ths of a
Michael_ 0:61d83318f2d6 328 // deg C or F scales.
Michael_ 0:61d83318f2d6 329 float answer, remaining_count, count_per_degree;
Michael_ 0:61d83318f2d6 330 int reading;
Michael_ 0:61d83318f2d6 331 read_RAM();
Michael_ 0:61d83318f2d6 332 reading = (RAM[1] << 8) + RAM[0];
Michael_ 0:61d83318f2d6 333 if (reading & 0x8000) { // negative degrees C
Michael_ 0:61d83318f2d6 334 reading = 0-((reading ^ 0xffff) + 1); // 2's comp then convert to signed int
Michael_ 0:61d83318f2d6 335 }
Michael_ 0:61d83318f2d6 336 remaining_count = RAM[6];
Michael_ 0:61d83318f2d6 337 count_per_degree = RAM[7];
Michael_ 0:61d83318f2d6 338 answer = reading +0.0;
Michael_ 0:61d83318f2d6 339 answer = answer - 0.25 + (count_per_degree - remaining_count) / count_per_degree;
Michael_ 0:61d83318f2d6 340 if (scale=='C' or scale=='c')
Michael_ 0:61d83318f2d6 341 answer = answer / 2.0;
Michael_ 0:61d83318f2d6 342 else
Michael_ 0:61d83318f2d6 343 // Convert to deg F
Michael_ 0:61d83318f2d6 344 answer = answer * 9.0 / 10.0 + 32.0;
Michael_ 0:61d83318f2d6 345 return answer;
Michael_ 0:61d83318f2d6 346 }
Michael_ 0:61d83318f2d6 347
Michael_ 0:61d83318f2d6 348 bool DS1820::read_power_supply(devices device) {
Michael_ 0:61d83318f2d6 349 // This will return true if the device (or all devices) are Vcc powered
Michael_ 0:61d83318f2d6 350 // This will return false if the device (or ANY device) is parasite powered
Michael_ 0:61d83318f2d6 351 if (device==all_devices)
Michael_ 0:61d83318f2d6 352 skip_ROM(); // Skip ROM command, will poll for any device using parasite power
Michael_ 0:61d83318f2d6 353 else
Michael_ 0:61d83318f2d6 354 match_ROM();
Michael_ 0:61d83318f2d6 355 onewire_byte_out(0xB4); // Read power supply command
Michael_ 0:61d83318f2d6 356 return onewire_bit_in();
Michael_ 0:61d83318f2d6 357 }