Alastair D'Silva / DS1820

A cut-down version of https://os.mbed.com/users/Sissors/code/DS1820/ tweaked for use with the STM32F103. It is all generic Mbed operations though, so should be usable anywhere. Non-essential functions have been removed, as this is intended for use within a tutorial.

Dependencies:   LinkedList

Dependents:   STM32F103C8T6_DS18B20 stm32f103c8t6-ds18b20

Fork of DS1820 by Erik -

DS1820.cpp@17:045f96704cc6, 2018-01-12 (annotated)

Committer:
deece
Date:
Fri Jan 12 00:38:01 2018 +0000
Revision:
17:045f96704cc6
Parent:
16:d490e11c466d
Child:
18:3a24aedc1e7c
Child:
19:b9d69bad8185
Working

Who changed what in which revision?

UserRevisionLine numberNew contents of line
pairmand 3:8f2b7f4940b5 1 #include "DS1820.h"
Sissors 5:2cd4928e8147 2
deece 16:d490e11c466d 3 static inline void onewire_input(DigitalInOut &pin) {
deece 16:d490e11c466d 4 pin.input();
deece 16:d490e11c466d 5 }
Sissors 14:c591209285e9 6
deece 16:d490e11c466d 7 static inline void onewire_output(DigitalInOut &pin) {
deece 16:d490e11c466d 8 pin.output();
deece 16:d490e11c466d 9 pin.write(0);
deece 16:d490e11c466d 10 }
Sissors 14:c591209285e9 11
Sissors 5:2cd4928e8147 12 LinkedList<node> DS1820::probes;
pairmand 3:8f2b7f4940b5 13
pairmand 3:8f2b7f4940b5 14
deece 16:d490e11c466d 15 DS1820::DS1820 (PinName data_pin) : _datapin(data_pin) {
pairmand 3:8f2b7f4940b5 16 int byte_counter;
deece 16:d490e11c466d 17
deece 16:d490e11c466d 18 tracer = 1;
florian 9:3821ca0b7f14 19
pairmand 3:8f2b7f4940b5 20 for(byte_counter=0;byte_counter<9;byte_counter++)
pairmand 3:8f2b7f4940b5 21 RAM[byte_counter] = 0x00;
Sissors 5:2cd4928e8147 22
deece 16:d490e11c466d 23 onewire_input(_datapin);
Sissors 14:c591209285e9 24
deece 16:d490e11c466d 25 if (!unassignedProbe(_ROM))
deece 16:d490e11c466d 26 error("No unassigned DS1820 found!\r\n");
Sissors 5:2cd4928e8147 27 else {
deece 16:d490e11c466d 28 onewire_input(_datapin);
Sissors 5:2cd4928e8147 29 probes.append(this);
Sissors 5:2cd4928e8147 30 }
pairmand 3:8f2b7f4940b5 31 }
Sissors 5:2cd4928e8147 32
Sissors 5:2cd4928e8147 33 DS1820::~DS1820 (void) {
Sissors 5:2cd4928e8147 34 node *tmp;
Sissors 5:2cd4928e8147 35 for(int i=1; i<=probes.length(); i++)
Sissors 5:2cd4928e8147 36 {
Sissors 5:2cd4928e8147 37 tmp = probes.pop(i);
Sissors 5:2cd4928e8147 38 if (tmp->data == this)
Sissors 5:2cd4928e8147 39 probes.remove(i);
Sissors 5:2cd4928e8147 40 }
pairmand 3:8f2b7f4940b5 41 }
Sissors 5:2cd4928e8147 42
pairmand 3:8f2b7f4940b5 43
deece 16:d490e11c466d 44 bool DS1820::onewire_reset() {
pairmand 3:8f2b7f4940b5 45 // This will return false if no devices are present on the data bus
pairmand 3:8f2b7f4940b5 46 bool presence=false;
deece 16:d490e11c466d 47 onewire_output(_datapin); // bring low for 500 us
pairmand 3:8f2b7f4940b5 48 wait_us(500);
deece 16:d490e11c466d 49 onewire_input(_datapin); // let the data line float high
pairmand 3:8f2b7f4940b5 50 wait_us(90); // wait 90us
deece 16:d490e11c466d 51 if (_datapin.read()==0) // see if any devices are pulling the data line low
pairmand 3:8f2b7f4940b5 52 presence=true;
pairmand 3:8f2b7f4940b5 53 wait_us(410);
pairmand 3:8f2b7f4940b5 54 return presence;
pairmand 3:8f2b7f4940b5 55 }
pairmand 3:8f2b7f4940b5 56
deece 16:d490e11c466d 57 void DS1820::onewire_bit_out (bool bit_data) {
deece 16:d490e11c466d 58 onewire_output(_datapin);
deece 16:d490e11c466d 59 wait_us(1); // DXP modified from 5
deece 17:045f96704cc6 60 if (!bit_data) {
deece 17:045f96704cc6 61 wait_us(57); // keep data line low
pairmand 3:8f2b7f4940b5 62 }
deece 17:045f96704cc6 63 onewire_input(_datapin);
deece 17:045f96704cc6 64 wait_us(50);
pairmand 3:8f2b7f4940b5 65 }
pairmand 3:8f2b7f4940b5 66
pairmand 3:8f2b7f4940b5 67 void DS1820::onewire_byte_out(char data) { // output data character (least sig bit first).
deece 17:045f96704cc6 68 for (int n=0; n<8; n++) {
deece 16:d490e11c466d 69 onewire_bit_out(data & 0x01);
pairmand 3:8f2b7f4940b5 70 data = data >> 1; // now the next bit is in the least sig bit position.
pairmand 3:8f2b7f4940b5 71 }
deece 16:d490e11c466d 72 wait_us(100);
pairmand 3:8f2b7f4940b5 73 }
pairmand 3:8f2b7f4940b5 74
deece 16:d490e11c466d 75 bool DS1820::onewire_bit_in() {
pairmand 3:8f2b7f4940b5 76 bool answer;
deece 16:d490e11c466d 77 onewire_output(_datapin);
deece 16:d490e11c466d 78 wait_us(1); // DXP modified from 5
deece 16:d490e11c466d 79 onewire_input(_datapin);
pairmand 3:8f2b7f4940b5 80 wait_us(10); // DXP modified from 5
deece 16:d490e11c466d 81 answer = _datapin.read();
deece 16:d490e11c466d 82 wait_us(49); // DXP modified from 50
pairmand 3:8f2b7f4940b5 83 return answer;
pairmand 3:8f2b7f4940b5 84 }
pairmand 3:8f2b7f4940b5 85
pairmand 3:8f2b7f4940b5 86 char DS1820::onewire_byte_in() { // read byte, least sig byte first
pairmand 3:8f2b7f4940b5 87 char answer = 0x00;
pairmand 3:8f2b7f4940b5 88 int i;
pairmand 3:8f2b7f4940b5 89 for (i=0; i<8; i++) {
pairmand 3:8f2b7f4940b5 90 answer = answer >> 1; // shift over to make room for the next bit
deece 16:d490e11c466d 91 if (onewire_bit_in())
pairmand 3:8f2b7f4940b5 92 answer = answer | 0x80; // if the data port is high, make this bit a 1
pairmand 3:8f2b7f4940b5 93 }
pairmand 3:8f2b7f4940b5 94 return answer;
pairmand 3:8f2b7f4940b5 95 }
Sissors 5:2cd4928e8147 96
deece 16:d490e11c466d 97
deece 16:d490e11c466d 98 bool DS1820::unassignedProbe(char *ROM_address) {
deece 16:d490e11c466d 99 return search_ROM_routine(0xF0, ROM_address);
pairmand 3:8f2b7f4940b5 100 }
pairmand 3:8f2b7f4940b5 101
deece 16:d490e11c466d 102 bool DS1820::search_ROM_routine(char command, char *ROM_address) {
Sissors 5:2cd4928e8147 103 bool DS1820_done_flag = false;
Sissors 5:2cd4928e8147 104 int DS1820_last_descrepancy = 0;
Sissors 5:2cd4928e8147 105 char DS1820_search_ROM[8] = {0, 0, 0, 0, 0, 0, 0, 0};
Sissors 5:2cd4928e8147 106
pairmand 3:8f2b7f4940b5 107 int descrepancy_marker, ROM_bit_index;
pairmand 3:8f2b7f4940b5 108 bool return_value, Bit_A, Bit_B;
pairmand 3:8f2b7f4940b5 109 char byte_counter, bit_mask;
pairmand 3:8f2b7f4940b5 110
pairmand 3:8f2b7f4940b5 111 return_value=false;
Sissors 5:2cd4928e8147 112 while (!DS1820_done_flag) {
deece 16:d490e11c466d 113 if (!onewire_reset()) {
Sissors 5:2cd4928e8147 114 return false;
pairmand 3:8f2b7f4940b5 115 } else {
pairmand 3:8f2b7f4940b5 116 ROM_bit_index=1;
pairmand 3:8f2b7f4940b5 117 descrepancy_marker=0;
Sissors 12:196e9e54b033 118 char command_shift = command;
Sissors 5:2cd4928e8147 119 for (int n=0; n<8; n++) { // Search ROM command or Search Alarm command
deece 16:d490e11c466d 120 onewire_bit_out(command_shift & 0x01);
Sissors 12:196e9e54b033 121 command_shift = command_shift >> 1; // now the next bit is in the least sig bit position.
Sissors 5:2cd4928e8147 122 }
deece 16:d490e11c466d 123 wait_us(100);
deece 16:d490e11c466d 124
pairmand 3:8f2b7f4940b5 125 byte_counter = 0;
pairmand 3:8f2b7f4940b5 126 bit_mask = 0x01;
pairmand 3:8f2b7f4940b5 127 while (ROM_bit_index<=64) {
deece 16:d490e11c466d 128 Bit_A = onewire_bit_in();
deece 16:d490e11c466d 129 Bit_B = onewire_bit_in();
pairmand 3:8f2b7f4940b5 130 if (Bit_A & Bit_B) {
pairmand 3:8f2b7f4940b5 131 descrepancy_marker = 0; // data read error, this should never happen
pairmand 3:8f2b7f4940b5 132 ROM_bit_index = 0xFF;
pairmand 3:8f2b7f4940b5 133 } else {
pairmand 3:8f2b7f4940b5 134 if (Bit_A | Bit_B) {
pairmand 3:8f2b7f4940b5 135 // Set ROM bit to Bit_A
pairmand 3:8f2b7f4940b5 136 if (Bit_A) {
pairmand 3:8f2b7f4940b5 137 DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] | bit_mask; // Set ROM bit to one
pairmand 3:8f2b7f4940b5 138 } else {
pairmand 3:8f2b7f4940b5 139 DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] & ~bit_mask; // Set ROM bit to zero
pairmand 3:8f2b7f4940b5 140 }
pairmand 3:8f2b7f4940b5 141 } else {
pairmand 3:8f2b7f4940b5 142 // both bits A and B are low, so there are two or more devices present
pairmand 3:8f2b7f4940b5 143 if ( ROM_bit_index == DS1820_last_descrepancy ) {
pairmand 3:8f2b7f4940b5 144 DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] | bit_mask; // Set ROM bit to one
pairmand 3:8f2b7f4940b5 145 } else {
pairmand 3:8f2b7f4940b5 146 if ( ROM_bit_index > DS1820_last_descrepancy ) {
pairmand 3:8f2b7f4940b5 147 DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] & ~bit_mask; // Set ROM bit to zero
pairmand 3:8f2b7f4940b5 148 descrepancy_marker = ROM_bit_index;
pairmand 3:8f2b7f4940b5 149 } else {
pairmand 3:8f2b7f4940b5 150 if (( DS1820_search_ROM[byte_counter] & bit_mask) == 0x00 )
pairmand 3:8f2b7f4940b5 151 descrepancy_marker = ROM_bit_index;
pairmand 3:8f2b7f4940b5 152 }
pairmand 3:8f2b7f4940b5 153 }
pairmand 3:8f2b7f4940b5 154 }
deece 16:d490e11c466d 155 onewire_bit_out (DS1820_search_ROM[byte_counter] & bit_mask);
pairmand 3:8f2b7f4940b5 156 ROM_bit_index++;
pairmand 3:8f2b7f4940b5 157 if (bit_mask & 0x80) {
pairmand 3:8f2b7f4940b5 158 byte_counter++;
pairmand 3:8f2b7f4940b5 159 bit_mask = 0x01;
pairmand 3:8f2b7f4940b5 160 } else {
pairmand 3:8f2b7f4940b5 161 bit_mask = bit_mask << 1;
pairmand 3:8f2b7f4940b5 162 }
pairmand 3:8f2b7f4940b5 163 }
deece 16:d490e11c466d 164
deece 16:d490e11c466d 165 wait_us(100);
pairmand 3:8f2b7f4940b5 166 }
pairmand 3:8f2b7f4940b5 167 DS1820_last_descrepancy = descrepancy_marker;
pairmand 3:8f2b7f4940b5 168 if (ROM_bit_index != 0xFF) {
Sissors 5:2cd4928e8147 169 int i = 1;
Sissors 5:2cd4928e8147 170 node *list_container;
Sissors 5:2cd4928e8147 171 while(1) {
Sissors 5:2cd4928e8147 172 list_container = probes.pop(i);
Sissors 5:2cd4928e8147 173 if (list_container == NULL) { //End of list, or empty list
Sissors 5:2cd4928e8147 174 if (ROM_checksum_error(DS1820_search_ROM)) { // Check the CRC
Sissors 5:2cd4928e8147 175 return false;
Sissors 5:2cd4928e8147 176 }
Sissors 5:2cd4928e8147 177 for(byte_counter=0;byte_counter<8;byte_counter++)
Sissors 5:2cd4928e8147 178 ROM_address[byte_counter] = DS1820_search_ROM[byte_counter];
deece 16:d490e11c466d 179
deece 16:d490e11c466d 180 printf("Found DS18B20: %02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x\r\n",
deece 16:d490e11c466d 181 ROM_address[0], ROM_address[1], ROM_address[2], ROM_address[3], ROM_address[4], ROM_address[5], ROM_address[6], ROM_address[7]);
Sissors 5:2cd4928e8147 182 return true;
Sissors 5:2cd4928e8147 183 } else { //Otherwise, check if ROM is already known
Sissors 5:2cd4928e8147 184 bool equal = true;
Sissors 5:2cd4928e8147 185 DS1820 *pointer = (DS1820*) list_container->data;
Sissors 5:2cd4928e8147 186 char *ROM_compare = pointer->_ROM;
Sissors 5:2cd4928e8147 187
Sissors 5:2cd4928e8147 188 for(byte_counter=0;byte_counter<8;byte_counter++) {
Sissors 5:2cd4928e8147 189 if ( ROM_compare[byte_counter] != DS1820_search_ROM[byte_counter])
Sissors 5:2cd4928e8147 190 equal = false;
Sissors 5:2cd4928e8147 191 }
Sissors 5:2cd4928e8147 192 if (equal)
Sissors 5:2cd4928e8147 193 break;
Sissors 5:2cd4928e8147 194 else
Sissors 5:2cd4928e8147 195 i++;
Sissors 5:2cd4928e8147 196 }
Sissors 5:2cd4928e8147 197 }
pairmand 3:8f2b7f4940b5 198 }
pairmand 3:8f2b7f4940b5 199 }
pairmand 3:8f2b7f4940b5 200 if (DS1820_last_descrepancy == 0)
pairmand 3:8f2b7f4940b5 201 DS1820_done_flag = true;
pairmand 3:8f2b7f4940b5 202 }
pairmand 3:8f2b7f4940b5 203 return return_value;
pairmand 3:8f2b7f4940b5 204 }
pairmand 3:8f2b7f4940b5 205
pairmand 3:8f2b7f4940b5 206 void DS1820::match_ROM() {
pairmand 3:8f2b7f4940b5 207 // Used to select a specific device
pairmand 3:8f2b7f4940b5 208 int i;
deece 16:d490e11c466d 209 onewire_reset();
deece 16:d490e11c466d 210 onewire_byte_out(0x55); //Match ROM command
Sissors 5:2cd4928e8147 211 for (i=0;i<8;i++) {
Sissors 5:2cd4928e8147 212 onewire_byte_out(_ROM[i]);
Sissors 5:2cd4928e8147 213 }
pairmand 3:8f2b7f4940b5 214 }
pairmand 3:8f2b7f4940b5 215
pairmand 3:8f2b7f4940b5 216 void DS1820::skip_ROM() {
deece 16:d490e11c466d 217 onewire_reset();
pairmand 3:8f2b7f4940b5 218 onewire_byte_out(0xCC); // Skip ROM command
pairmand 3:8f2b7f4940b5 219 }
pairmand 3:8f2b7f4940b5 220
Sissors 5:2cd4928e8147 221 bool DS1820::ROM_checksum_error(char *_ROM_address) {
Sissors 11:1a3c3002b50c 222 char _CRC=0x00;
pairmand 3:8f2b7f4940b5 223 int i;
pairmand 3:8f2b7f4940b5 224 for(i=0;i<7;i++) // Only going to shift the lower 7 bytes
Sissors 11:1a3c3002b50c 225 _CRC = CRC_byte(_CRC, _ROM_address[i]);
pairmand 3:8f2b7f4940b5 226 // After 7 bytes CRC should equal the 8th byte (ROM CRC)
Sissors 11:1a3c3002b50c 227 return (_CRC!=_ROM_address[7]); // will return true if there is a CRC checksum mis-match
pairmand 3:8f2b7f4940b5 228 }
pairmand 3:8f2b7f4940b5 229
pairmand 3:8f2b7f4940b5 230 bool DS1820::RAM_checksum_error() {
Sissors 11:1a3c3002b50c 231 char _CRC=0x00;
pairmand 3:8f2b7f4940b5 232 int i;
pairmand 3:8f2b7f4940b5 233 for(i=0;i<8;i++) // Only going to shift the lower 8 bytes
Sissors 11:1a3c3002b50c 234 _CRC = CRC_byte(_CRC, RAM[i]);
pairmand 3:8f2b7f4940b5 235 // After 8 bytes CRC should equal the 9th byte (RAM CRC)
Sissors 11:1a3c3002b50c 236 return (_CRC!=RAM[8]); // will return true if there is a CRC checksum mis-match
pairmand 3:8f2b7f4940b5 237 }
pairmand 3:8f2b7f4940b5 238
Sissors 11:1a3c3002b50c 239 char DS1820::CRC_byte (char _CRC, char byte ) {
pairmand 3:8f2b7f4940b5 240 int j;
pairmand 3:8f2b7f4940b5 241 for(j=0;j<8;j++) {
Sissors 11:1a3c3002b50c 242 if ((byte & 0x01 ) ^ (_CRC & 0x01)) {
pairmand 3:8f2b7f4940b5 243 // DATA ^ LSB CRC = 1
Sissors 11:1a3c3002b50c 244 _CRC = _CRC>>1;
pairmand 3:8f2b7f4940b5 245 // Set the MSB to 1
Sissors 11:1a3c3002b50c 246 _CRC = _CRC | 0x80;
pairmand 3:8f2b7f4940b5 247 // Check bit 3
Sissors 11:1a3c3002b50c 248 if (_CRC & 0x04) {
Sissors 11:1a3c3002b50c 249 _CRC = _CRC & 0xFB; // Bit 3 is set, so clear it
pairmand 3:8f2b7f4940b5 250 } else {
Sissors 11:1a3c3002b50c 251 _CRC = _CRC | 0x04; // Bit 3 is clear, so set it
pairmand 3:8f2b7f4940b5 252 }
pairmand 3:8f2b7f4940b5 253 // Check bit 4
Sissors 11:1a3c3002b50c 254 if (_CRC & 0x08) {
Sissors 11:1a3c3002b50c 255 _CRC = _CRC & 0xF7; // Bit 4 is set, so clear it
pairmand 3:8f2b7f4940b5 256 } else {
Sissors 11:1a3c3002b50c 257 _CRC = _CRC | 0x08; // Bit 4 is clear, so set it
pairmand 3:8f2b7f4940b5 258 }
pairmand 3:8f2b7f4940b5 259 } else {
pairmand 3:8f2b7f4940b5 260 // DATA ^ LSB CRC = 0
Sissors 11:1a3c3002b50c 261 _CRC = _CRC>>1;
pairmand 3:8f2b7f4940b5 262 // clear MSB
Sissors 11:1a3c3002b50c 263 _CRC = _CRC & 0x7F;
pairmand 3:8f2b7f4940b5 264 // No need to check bits, with DATA ^ LSB CRC = 0, they will remain unchanged
pairmand 3:8f2b7f4940b5 265 }
pairmand 3:8f2b7f4940b5 266 byte = byte>>1;
pairmand 3:8f2b7f4940b5 267 }
Sissors 11:1a3c3002b50c 268 return _CRC;
pairmand 3:8f2b7f4940b5 269 }
pairmand 3:8f2b7f4940b5 270
Sissors 5:2cd4928e8147 271 int DS1820::convertTemperature(bool wait, devices device) {
pairmand 3:8f2b7f4940b5 272 // Convert temperature into scratchpad RAM for all devices at once
deece 17:045f96704cc6 273 int delay_time = 850; // Default delay time
pairmand 3:8f2b7f4940b5 274 if (device==all_devices)
pairmand 3:8f2b7f4940b5 275 skip_ROM(); // Skip ROM command, will convert for ALL devices
pairmand 3:8f2b7f4940b5 276 else {
pairmand 3:8f2b7f4940b5 277 match_ROM();
pairmand 3:8f2b7f4940b5 278 }
Sissors 5:2cd4928e8147 279
deece 17:045f96704cc6 280 onewire_byte_out(0x44); // perform temperature conversion
deece 16:d490e11c466d 281
deece 16:d490e11c466d 282 if (wait) {
deece 16:d490e11c466d 283 wait_ms(delay_time);
pairmand 3:8f2b7f4940b5 284 }
pairmand 3:8f2b7f4940b5 285 return delay_time;
pairmand 3:8f2b7f4940b5 286 }
pairmand 3:8f2b7f4940b5 287
pairmand 3:8f2b7f4940b5 288 void DS1820::read_RAM() {
pairmand 3:8f2b7f4940b5 289 // This will copy the DS1820's 9 bytes of RAM data
pairmand 3:8f2b7f4940b5 290 // into the objects RAM array. Functions that use
pairmand 3:8f2b7f4940b5 291 // RAM values will automaticly call this procedure.
pairmand 3:8f2b7f4940b5 292 int i;
pairmand 3:8f2b7f4940b5 293 match_ROM(); // Select this device
pairmand 3:8f2b7f4940b5 294 onewire_byte_out( 0xBE); //Read Scratchpad command
pairmand 3:8f2b7f4940b5 295 for(i=0;i<9;i++) {
pairmand 3:8f2b7f4940b5 296 RAM[i] = onewire_byte_in();
pairmand 3:8f2b7f4940b5 297 }
deece 17:045f96704cc6 298 printf("Scratchpad=%02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x\r\n",
deece 17:045f96704cc6 299 RAM[8], RAM[7], RAM[6], RAM[5], RAM[4], RAM[3], RAM[2], RAM[1], RAM[0]);
deece 17:045f96704cc6 300 printf("Checksum is %s\r\n", RAM_checksum_error() ? "bad" : "good");
pairmand 3:8f2b7f4940b5 301 }
pairmand 3:8f2b7f4940b5 302
Sissors 5:2cd4928e8147 303 bool DS1820::setResolution(unsigned int resolution) {
pairmand 3:8f2b7f4940b5 304 bool answer = false;
pairmand 3:8f2b7f4940b5 305 resolution = resolution - 9;
pairmand 3:8f2b7f4940b5 306 if (resolution < 4) {
pairmand 3:8f2b7f4940b5 307 resolution = resolution<<5; // align the bits
pairmand 3:8f2b7f4940b5 308 RAM[4] = (RAM[4] & 0x60) | resolution; // mask out old data, insert new
pairmand 3:8f2b7f4940b5 309 write_scratchpad ((RAM[2]<<8) + RAM[3]);
pairmand 3:8f2b7f4940b5 310 // store_scratchpad (DS1820::this_device); // Need to test if this is required
pairmand 3:8f2b7f4940b5 311 answer = true;
pairmand 3:8f2b7f4940b5 312 }
pairmand 3:8f2b7f4940b5 313 return answer;
pairmand 3:8f2b7f4940b5 314 }
pairmand 3:8f2b7f4940b5 315
pairmand 3:8f2b7f4940b5 316 void DS1820::write_scratchpad(int data) {
pairmand 3:8f2b7f4940b5 317 RAM[3] = data;
pairmand 3:8f2b7f4940b5 318 RAM[2] = data>>8;
pairmand 3:8f2b7f4940b5 319 match_ROM();
pairmand 3:8f2b7f4940b5 320 onewire_byte_out(0x4E); // Copy scratchpad into DS1820 ram memory
pairmand 3:8f2b7f4940b5 321 onewire_byte_out(RAM[2]); // T(H)
pairmand 3:8f2b7f4940b5 322 onewire_byte_out(RAM[3]); // T(L)
Sissors 5:2cd4928e8147 323 if ((FAMILY_CODE == FAMILY_CODE_DS18B20 ) || (FAMILY_CODE == FAMILY_CODE_DS1822 )) {
pairmand 3:8f2b7f4940b5 324 onewire_byte_out(RAM[4]); // Configuration register
pairmand 3:8f2b7f4940b5 325 }
pairmand 3:8f2b7f4940b5 326 }
pairmand 3:8f2b7f4940b5 327
pairmand 3:8f2b7f4940b5 328 float DS1820::temperature(char scale) {
pairmand 3:8f2b7f4940b5 329 // The data specs state that count_per_degree should be 0x10 (16), I found my devices
pairmand 3:8f2b7f4940b5 330 // to have a count_per_degree of 0x4B (75). With the standard resolution of 1/2 deg C
pairmand 3:8f2b7f4940b5 331 // this allowed an expanded resolution of 1/150th of a deg C. I wouldn't rely on this
pairmand 3:8f2b7f4940b5 332 // being super acurate, but it does allow for a smooth display in the 1/10ths of a
pairmand 3:8f2b7f4940b5 333 // deg C or F scales.
pairmand 3:8f2b7f4940b5 334 float answer, remaining_count, count_per_degree;
pairmand 3:8f2b7f4940b5 335 int reading;
pairmand 3:8f2b7f4940b5 336 read_RAM();
pairmand 3:8f2b7f4940b5 337 if (RAM_checksum_error())
pairmand 3:8f2b7f4940b5 338 // Indicate we got a CRC error
Sissors 7:58b61681818f 339 answer = invalid_conversion;
pairmand 3:8f2b7f4940b5 340 else {
pairmand 3:8f2b7f4940b5 341 reading = (RAM[1] << 8) + RAM[0];
pairmand 3:8f2b7f4940b5 342 if (reading & 0x8000) { // negative degrees C
pairmand 3:8f2b7f4940b5 343 reading = 0-((reading ^ 0xffff) + 1); // 2's comp then convert to signed int
pairmand 3:8f2b7f4940b5 344 }
pairmand 3:8f2b7f4940b5 345 answer = reading +0.0; // convert to floating point
Sissors 5:2cd4928e8147 346 if ((FAMILY_CODE == FAMILY_CODE_DS18B20 ) || (FAMILY_CODE == FAMILY_CODE_DS1822 )) {
Sissors 11:1a3c3002b50c 347 answer = answer / 16.0f;
pairmand 3:8f2b7f4940b5 348 }
pairmand 3:8f2b7f4940b5 349 else {
pairmand 3:8f2b7f4940b5 350 remaining_count = RAM[6];
pairmand 3:8f2b7f4940b5 351 count_per_degree = RAM[7];
Sissors 11:1a3c3002b50c 352 answer = floor(answer/2.0f) - 0.25f + (count_per_degree - remaining_count) / count_per_degree;
pairmand 3:8f2b7f4940b5 353 }
florian 10:d297ce9ce422 354 if (scale=='F' or scale=='f')
pairmand 3:8f2b7f4940b5 355 // Convert to deg F
Sissors 11:1a3c3002b50c 356 answer = answer * 9.0f / 5.0f + 32.0f;
pairmand 3:8f2b7f4940b5 357 }
pairmand 3:8f2b7f4940b5 358 return answer;
pairmand 3:8f2b7f4940b5 359 }
pairmand 3:8f2b7f4940b5 360
pairmand 3:8f2b7f4940b5 361