Erik - / DS1820

Library for reading temperature from DS1820, DS18B20 and DS1822

Dependencies:   LinkedList

Dependents:   heatmap BLE_Temperature BLE_Temperature_Exercise F334andDS18B20 ... more

Fork of DS1820 by David Pairman

HelloWorld: http://mbed.org/users/Sissors/code/DS1820_HelloWorld/

Library should currently work on all mbed targets, let me know if there is an issue. First however make sure you have latest version of mbed library and this library.

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 }