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@16:d490e11c466d, 2018-01-11 (annotated)

Committer:
deece
Date:
Thu Jan 11 04:37:42 2018 +0000
Revision:
16:d490e11c466d
Parent:
14:c591209285e9
Child:
17:045f96704cc6
Broken - always gives a reading of 85C

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 DigitalOut tracer(PA_6);
Sissors 14:c591209285e9 4
deece 16:d490e11c466d 5 static inline void onewire_input(DigitalInOut &pin) {
deece 16:d490e11c466d 6 pin.input();
deece 16:d490e11c466d 7 pin.mode(PullUp);
deece 16:d490e11c466d 8 }
Sissors 14:c591209285e9 9
deece 16:d490e11c466d 10 static inline void onewire_output(DigitalInOut &pin) {
deece 16:d490e11c466d 11 pin.output();
deece 16:d490e11c466d 12 pin.write(0);
deece 16:d490e11c466d 13 }
Sissors 14:c591209285e9 14
Sissors 5:2cd4928e8147 15 LinkedList<node> DS1820::probes;
pairmand 3:8f2b7f4940b5 16
pairmand 3:8f2b7f4940b5 17
deece 16:d490e11c466d 18 DS1820::DS1820 (PinName data_pin) : _datapin(data_pin) {
pairmand 3:8f2b7f4940b5 19 int byte_counter;
deece 16:d490e11c466d 20
deece 16:d490e11c466d 21 tracer = 1;
florian 9:3821ca0b7f14 22
pairmand 3:8f2b7f4940b5 23 for(byte_counter=0;byte_counter<9;byte_counter++)
pairmand 3:8f2b7f4940b5 24 RAM[byte_counter] = 0x00;
Sissors 5:2cd4928e8147 25
deece 16:d490e11c466d 26 onewire_input(_datapin);
Sissors 14:c591209285e9 27
deece 16:d490e11c466d 28 if (!unassignedProbe(_ROM))
deece 16:d490e11c466d 29 error("No unassigned DS1820 found!\r\n");
Sissors 5:2cd4928e8147 30 else {
deece 16:d490e11c466d 31 onewire_input(_datapin);
Sissors 5:2cd4928e8147 32 probes.append(this);
Sissors 5:2cd4928e8147 33 }
pairmand 3:8f2b7f4940b5 34 }
Sissors 5:2cd4928e8147 35
Sissors 5:2cd4928e8147 36 DS1820::~DS1820 (void) {
Sissors 5:2cd4928e8147 37 node *tmp;
Sissors 5:2cd4928e8147 38 for(int i=1; i<=probes.length(); i++)
Sissors 5:2cd4928e8147 39 {
Sissors 5:2cd4928e8147 40 tmp = probes.pop(i);
Sissors 5:2cd4928e8147 41 if (tmp->data == this)
Sissors 5:2cd4928e8147 42 probes.remove(i);
Sissors 5:2cd4928e8147 43 }
pairmand 3:8f2b7f4940b5 44 }
Sissors 5:2cd4928e8147 45
pairmand 3:8f2b7f4940b5 46
deece 16:d490e11c466d 47 bool DS1820::onewire_reset() {
pairmand 3:8f2b7f4940b5 48 // This will return false if no devices are present on the data bus
pairmand 3:8f2b7f4940b5 49 bool presence=false;
deece 16:d490e11c466d 50 onewire_output(_datapin); // bring low for 500 us
pairmand 3:8f2b7f4940b5 51 wait_us(500);
deece 16:d490e11c466d 52 onewire_input(_datapin); // let the data line float high
pairmand 3:8f2b7f4940b5 53 wait_us(90); // wait 90us
deece 16:d490e11c466d 54 if (_datapin.read()==0) // see if any devices are pulling the data line low
pairmand 3:8f2b7f4940b5 55 presence=true;
pairmand 3:8f2b7f4940b5 56 wait_us(410);
pairmand 3:8f2b7f4940b5 57 return presence;
pairmand 3:8f2b7f4940b5 58 }
pairmand 3:8f2b7f4940b5 59
deece 16:d490e11c466d 60 void DS1820::onewire_bit_out (bool bit_data) {
deece 16:d490e11c466d 61 onewire_output(_datapin);
deece 16:d490e11c466d 62 wait_us(1); // DXP modified from 5
pairmand 3:8f2b7f4940b5 63 if (bit_data) {
deece 16:d490e11c466d 64 onewire_input(_datapin); // bring data line high
pairmand 3:8f2b7f4940b5 65 } else {
deece 16:d490e11c466d 66 wait_us(57); // keep data line low
deece 16:d490e11c466d 67 onewire_input(_datapin);
pairmand 3:8f2b7f4940b5 68 }
deece 16:d490e11c466d 69 wait_us(55);
pairmand 3:8f2b7f4940b5 70 }
pairmand 3:8f2b7f4940b5 71
pairmand 3:8f2b7f4940b5 72 void DS1820::onewire_byte_out(char data) { // output data character (least sig bit first).
pairmand 3:8f2b7f4940b5 73 int n;
pairmand 3:8f2b7f4940b5 74 for (n=0; n<8; n++) {
deece 16:d490e11c466d 75 onewire_bit_out(data & 0x01);
pairmand 3:8f2b7f4940b5 76 data = data >> 1; // now the next bit is in the least sig bit position.
pairmand 3:8f2b7f4940b5 77 }
deece 16:d490e11c466d 78 wait_us(100);
pairmand 3:8f2b7f4940b5 79 }
pairmand 3:8f2b7f4940b5 80
deece 16:d490e11c466d 81 bool DS1820::onewire_bit_in() {
pairmand 3:8f2b7f4940b5 82 bool answer;
deece 16:d490e11c466d 83 onewire_output(_datapin);
deece 16:d490e11c466d 84 wait_us(1); // DXP modified from 5
deece 16:d490e11c466d 85 onewire_input(_datapin);
pairmand 3:8f2b7f4940b5 86 wait_us(10); // DXP modified from 5
deece 16:d490e11c466d 87 answer = _datapin.read();
deece 16:d490e11c466d 88 wait_us(49); // DXP modified from 50
pairmand 3:8f2b7f4940b5 89 return answer;
pairmand 3:8f2b7f4940b5 90 }
pairmand 3:8f2b7f4940b5 91
pairmand 3:8f2b7f4940b5 92 char DS1820::onewire_byte_in() { // read byte, least sig byte first
pairmand 3:8f2b7f4940b5 93 char answer = 0x00;
pairmand 3:8f2b7f4940b5 94 int i;
pairmand 3:8f2b7f4940b5 95 for (i=0; i<8; i++) {
pairmand 3:8f2b7f4940b5 96 answer = answer >> 1; // shift over to make room for the next bit
deece 16:d490e11c466d 97 if (onewire_bit_in())
pairmand 3:8f2b7f4940b5 98 answer = answer | 0x80; // if the data port is high, make this bit a 1
pairmand 3:8f2b7f4940b5 99 }
pairmand 3:8f2b7f4940b5 100 return answer;
pairmand 3:8f2b7f4940b5 101 }
Sissors 5:2cd4928e8147 102
deece 16:d490e11c466d 103
deece 16:d490e11c466d 104 bool DS1820::unassignedProbe(char *ROM_address) {
deece 16:d490e11c466d 105 return search_ROM_routine(0xF0, ROM_address);
pairmand 3:8f2b7f4940b5 106 }
pairmand 3:8f2b7f4940b5 107
deece 16:d490e11c466d 108 bool DS1820::search_ROM_routine(char command, char *ROM_address) {
Sissors 5:2cd4928e8147 109 bool DS1820_done_flag = false;
Sissors 5:2cd4928e8147 110 int DS1820_last_descrepancy = 0;
Sissors 5:2cd4928e8147 111 char DS1820_search_ROM[8] = {0, 0, 0, 0, 0, 0, 0, 0};
Sissors 5:2cd4928e8147 112
pairmand 3:8f2b7f4940b5 113 int descrepancy_marker, ROM_bit_index;
pairmand 3:8f2b7f4940b5 114 bool return_value, Bit_A, Bit_B;
pairmand 3:8f2b7f4940b5 115 char byte_counter, bit_mask;
pairmand 3:8f2b7f4940b5 116
pairmand 3:8f2b7f4940b5 117 return_value=false;
Sissors 5:2cd4928e8147 118 while (!DS1820_done_flag) {
deece 16:d490e11c466d 119 if (!onewire_reset()) {
Sissors 5:2cd4928e8147 120 return false;
pairmand 3:8f2b7f4940b5 121 } else {
pairmand 3:8f2b7f4940b5 122 ROM_bit_index=1;
pairmand 3:8f2b7f4940b5 123 descrepancy_marker=0;
Sissors 12:196e9e54b033 124 char command_shift = command;
Sissors 5:2cd4928e8147 125 for (int n=0; n<8; n++) { // Search ROM command or Search Alarm command
deece 16:d490e11c466d 126 onewire_bit_out(command_shift & 0x01);
Sissors 12:196e9e54b033 127 command_shift = command_shift >> 1; // now the next bit is in the least sig bit position.
Sissors 5:2cd4928e8147 128 }
deece 16:d490e11c466d 129 wait_us(100);
deece 16:d490e11c466d 130
pairmand 3:8f2b7f4940b5 131 byte_counter = 0;
pairmand 3:8f2b7f4940b5 132 bit_mask = 0x01;
pairmand 3:8f2b7f4940b5 133 while (ROM_bit_index<=64) {
deece 16:d490e11c466d 134 Bit_A = onewire_bit_in();
deece 16:d490e11c466d 135 Bit_B = onewire_bit_in();
pairmand 3:8f2b7f4940b5 136 if (Bit_A & Bit_B) {
pairmand 3:8f2b7f4940b5 137 descrepancy_marker = 0; // data read error, this should never happen
pairmand 3:8f2b7f4940b5 138 ROM_bit_index = 0xFF;
pairmand 3:8f2b7f4940b5 139 } else {
pairmand 3:8f2b7f4940b5 140 if (Bit_A | Bit_B) {
pairmand 3:8f2b7f4940b5 141 // Set ROM bit to Bit_A
pairmand 3:8f2b7f4940b5 142 if (Bit_A) {
pairmand 3:8f2b7f4940b5 143 DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] | bit_mask; // Set ROM bit to one
pairmand 3:8f2b7f4940b5 144 } else {
pairmand 3:8f2b7f4940b5 145 DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] & ~bit_mask; // Set ROM bit to zero
pairmand 3:8f2b7f4940b5 146 }
pairmand 3:8f2b7f4940b5 147 } else {
pairmand 3:8f2b7f4940b5 148 // both bits A and B are low, so there are two or more devices present
pairmand 3:8f2b7f4940b5 149 if ( ROM_bit_index == DS1820_last_descrepancy ) {
pairmand 3:8f2b7f4940b5 150 DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] | bit_mask; // Set ROM bit to one
pairmand 3:8f2b7f4940b5 151 } else {
pairmand 3:8f2b7f4940b5 152 if ( ROM_bit_index > DS1820_last_descrepancy ) {
pairmand 3:8f2b7f4940b5 153 DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] & ~bit_mask; // Set ROM bit to zero
pairmand 3:8f2b7f4940b5 154 descrepancy_marker = ROM_bit_index;
pairmand 3:8f2b7f4940b5 155 } else {
pairmand 3:8f2b7f4940b5 156 if (( DS1820_search_ROM[byte_counter] & bit_mask) == 0x00 )
pairmand 3:8f2b7f4940b5 157 descrepancy_marker = ROM_bit_index;
pairmand 3:8f2b7f4940b5 158 }
pairmand 3:8f2b7f4940b5 159 }
pairmand 3:8f2b7f4940b5 160 }
deece 16:d490e11c466d 161 onewire_bit_out (DS1820_search_ROM[byte_counter] & bit_mask);
pairmand 3:8f2b7f4940b5 162 ROM_bit_index++;
pairmand 3:8f2b7f4940b5 163 if (bit_mask & 0x80) {
pairmand 3:8f2b7f4940b5 164 byte_counter++;
pairmand 3:8f2b7f4940b5 165 bit_mask = 0x01;
pairmand 3:8f2b7f4940b5 166 } else {
pairmand 3:8f2b7f4940b5 167 bit_mask = bit_mask << 1;
pairmand 3:8f2b7f4940b5 168 }
pairmand 3:8f2b7f4940b5 169 }
deece 16:d490e11c466d 170
deece 16:d490e11c466d 171 wait_us(100);
pairmand 3:8f2b7f4940b5 172 }
pairmand 3:8f2b7f4940b5 173 DS1820_last_descrepancy = descrepancy_marker;
pairmand 3:8f2b7f4940b5 174 if (ROM_bit_index != 0xFF) {
Sissors 5:2cd4928e8147 175 int i = 1;
Sissors 5:2cd4928e8147 176 node *list_container;
Sissors 5:2cd4928e8147 177 while(1) {
Sissors 5:2cd4928e8147 178 list_container = probes.pop(i);
Sissors 5:2cd4928e8147 179 if (list_container == NULL) { //End of list, or empty list
Sissors 5:2cd4928e8147 180 if (ROM_checksum_error(DS1820_search_ROM)) { // Check the CRC
Sissors 5:2cd4928e8147 181 return false;
Sissors 5:2cd4928e8147 182 }
Sissors 5:2cd4928e8147 183 for(byte_counter=0;byte_counter<8;byte_counter++)
Sissors 5:2cd4928e8147 184 ROM_address[byte_counter] = DS1820_search_ROM[byte_counter];
deece 16:d490e11c466d 185
deece 16:d490e11c466d 186 printf("Found DS18B20: %02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x\r\n",
deece 16:d490e11c466d 187 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 188 return true;
Sissors 5:2cd4928e8147 189 } else { //Otherwise, check if ROM is already known
Sissors 5:2cd4928e8147 190 bool equal = true;
Sissors 5:2cd4928e8147 191 DS1820 *pointer = (DS1820*) list_container->data;
Sissors 5:2cd4928e8147 192 char *ROM_compare = pointer->_ROM;
Sissors 5:2cd4928e8147 193
Sissors 5:2cd4928e8147 194 for(byte_counter=0;byte_counter<8;byte_counter++) {
Sissors 5:2cd4928e8147 195 if ( ROM_compare[byte_counter] != DS1820_search_ROM[byte_counter])
Sissors 5:2cd4928e8147 196 equal = false;
Sissors 5:2cd4928e8147 197 }
Sissors 5:2cd4928e8147 198 if (equal)
Sissors 5:2cd4928e8147 199 break;
Sissors 5:2cd4928e8147 200 else
Sissors 5:2cd4928e8147 201 i++;
Sissors 5:2cd4928e8147 202 }
Sissors 5:2cd4928e8147 203 }
pairmand 3:8f2b7f4940b5 204 }
pairmand 3:8f2b7f4940b5 205 }
pairmand 3:8f2b7f4940b5 206 if (DS1820_last_descrepancy == 0)
pairmand 3:8f2b7f4940b5 207 DS1820_done_flag = true;
pairmand 3:8f2b7f4940b5 208 }
pairmand 3:8f2b7f4940b5 209 return return_value;
pairmand 3:8f2b7f4940b5 210 }
pairmand 3:8f2b7f4940b5 211
pairmand 3:8f2b7f4940b5 212 void DS1820::match_ROM() {
pairmand 3:8f2b7f4940b5 213 // Used to select a specific device
pairmand 3:8f2b7f4940b5 214 int i;
deece 16:d490e11c466d 215 onewire_reset();
deece 16:d490e11c466d 216 onewire_byte_out(0x55); //Match ROM command
Sissors 5:2cd4928e8147 217 for (i=0;i<8;i++) {
Sissors 5:2cd4928e8147 218 onewire_byte_out(_ROM[i]);
Sissors 5:2cd4928e8147 219 }
pairmand 3:8f2b7f4940b5 220 }
pairmand 3:8f2b7f4940b5 221
pairmand 3:8f2b7f4940b5 222 void DS1820::skip_ROM() {
deece 16:d490e11c466d 223 onewire_reset();
pairmand 3:8f2b7f4940b5 224 onewire_byte_out(0xCC); // Skip ROM command
pairmand 3:8f2b7f4940b5 225 }
pairmand 3:8f2b7f4940b5 226
Sissors 5:2cd4928e8147 227 bool DS1820::ROM_checksum_error(char *_ROM_address) {
Sissors 11:1a3c3002b50c 228 char _CRC=0x00;
pairmand 3:8f2b7f4940b5 229 int i;
pairmand 3:8f2b7f4940b5 230 for(i=0;i<7;i++) // Only going to shift the lower 7 bytes
Sissors 11:1a3c3002b50c 231 _CRC = CRC_byte(_CRC, _ROM_address[i]);
pairmand 3:8f2b7f4940b5 232 // After 7 bytes CRC should equal the 8th byte (ROM CRC)
Sissors 11:1a3c3002b50c 233 return (_CRC!=_ROM_address[7]); // will return true if there is a CRC checksum mis-match
pairmand 3:8f2b7f4940b5 234 }
pairmand 3:8f2b7f4940b5 235
pairmand 3:8f2b7f4940b5 236 bool DS1820::RAM_checksum_error() {
Sissors 11:1a3c3002b50c 237 char _CRC=0x00;
pairmand 3:8f2b7f4940b5 238 int i;
pairmand 3:8f2b7f4940b5 239 for(i=0;i<8;i++) // Only going to shift the lower 8 bytes
Sissors 11:1a3c3002b50c 240 _CRC = CRC_byte(_CRC, RAM[i]);
pairmand 3:8f2b7f4940b5 241 // After 8 bytes CRC should equal the 9th byte (RAM CRC)
Sissors 11:1a3c3002b50c 242 return (_CRC!=RAM[8]); // will return true if there is a CRC checksum mis-match
pairmand 3:8f2b7f4940b5 243 }
pairmand 3:8f2b7f4940b5 244
Sissors 11:1a3c3002b50c 245 char DS1820::CRC_byte (char _CRC, char byte ) {
pairmand 3:8f2b7f4940b5 246 int j;
pairmand 3:8f2b7f4940b5 247 for(j=0;j<8;j++) {
Sissors 11:1a3c3002b50c 248 if ((byte & 0x01 ) ^ (_CRC & 0x01)) {
pairmand 3:8f2b7f4940b5 249 // DATA ^ LSB CRC = 1
Sissors 11:1a3c3002b50c 250 _CRC = _CRC>>1;
pairmand 3:8f2b7f4940b5 251 // Set the MSB to 1
Sissors 11:1a3c3002b50c 252 _CRC = _CRC | 0x80;
pairmand 3:8f2b7f4940b5 253 // Check bit 3
Sissors 11:1a3c3002b50c 254 if (_CRC & 0x04) {
Sissors 11:1a3c3002b50c 255 _CRC = _CRC & 0xFB; // Bit 3 is set, so clear it
pairmand 3:8f2b7f4940b5 256 } else {
Sissors 11:1a3c3002b50c 257 _CRC = _CRC | 0x04; // Bit 3 is clear, so set it
pairmand 3:8f2b7f4940b5 258 }
pairmand 3:8f2b7f4940b5 259 // Check bit 4
Sissors 11:1a3c3002b50c 260 if (_CRC & 0x08) {
Sissors 11:1a3c3002b50c 261 _CRC = _CRC & 0xF7; // Bit 4 is set, so clear it
pairmand 3:8f2b7f4940b5 262 } else {
Sissors 11:1a3c3002b50c 263 _CRC = _CRC | 0x08; // Bit 4 is clear, so set it
pairmand 3:8f2b7f4940b5 264 }
pairmand 3:8f2b7f4940b5 265 } else {
pairmand 3:8f2b7f4940b5 266 // DATA ^ LSB CRC = 0
Sissors 11:1a3c3002b50c 267 _CRC = _CRC>>1;
pairmand 3:8f2b7f4940b5 268 // clear MSB
Sissors 11:1a3c3002b50c 269 _CRC = _CRC & 0x7F;
pairmand 3:8f2b7f4940b5 270 // No need to check bits, with DATA ^ LSB CRC = 0, they will remain unchanged
pairmand 3:8f2b7f4940b5 271 }
pairmand 3:8f2b7f4940b5 272 byte = byte>>1;
pairmand 3:8f2b7f4940b5 273 }
Sissors 11:1a3c3002b50c 274 return _CRC;
pairmand 3:8f2b7f4940b5 275 }
pairmand 3:8f2b7f4940b5 276
Sissors 5:2cd4928e8147 277 int DS1820::convertTemperature(bool wait, devices device) {
pairmand 3:8f2b7f4940b5 278 // Convert temperature into scratchpad RAM for all devices at once
pairmand 3:8f2b7f4940b5 279 int delay_time = 750; // Default delay time
pairmand 3:8f2b7f4940b5 280 char resolution;
pairmand 3:8f2b7f4940b5 281 if (device==all_devices)
pairmand 3:8f2b7f4940b5 282 skip_ROM(); // Skip ROM command, will convert for ALL devices
pairmand 3:8f2b7f4940b5 283 else {
pairmand 3:8f2b7f4940b5 284 match_ROM();
Sissors 5:2cd4928e8147 285 if ((FAMILY_CODE == FAMILY_CODE_DS18B20 ) || (FAMILY_CODE == FAMILY_CODE_DS1822 )) {
pairmand 3:8f2b7f4940b5 286 resolution = RAM[4] & 0x60;
pairmand 3:8f2b7f4940b5 287 if (resolution == 0x00) // 9 bits
pairmand 3:8f2b7f4940b5 288 delay_time = 94;
pairmand 3:8f2b7f4940b5 289 if (resolution == 0x20) // 10 bits
pairmand 3:8f2b7f4940b5 290 delay_time = 188;
pairmand 3:8f2b7f4940b5 291 if (resolution == 0x40) // 11 bits. Note 12bits uses the 750ms default
pairmand 3:8f2b7f4940b5 292 delay_time = 375;
pairmand 3:8f2b7f4940b5 293 }
pairmand 3:8f2b7f4940b5 294 }
Sissors 5:2cd4928e8147 295
deece 16:d490e11c466d 296 tracer = 0;
pairmand 3:8f2b7f4940b5 297 onewire_byte_out( 0x44); // perform temperature conversion
deece 16:d490e11c466d 298 tracer = 1;
deece 16:d490e11c466d 299
deece 16:d490e11c466d 300 if (wait) {
deece 16:d490e11c466d 301 wait_ms(delay_time);
deece 16:d490e11c466d 302 delay_time = 0;
pairmand 3:8f2b7f4940b5 303 }
pairmand 3:8f2b7f4940b5 304 return delay_time;
pairmand 3:8f2b7f4940b5 305 }
pairmand 3:8f2b7f4940b5 306
pairmand 3:8f2b7f4940b5 307 void DS1820::read_RAM() {
pairmand 3:8f2b7f4940b5 308 // This will copy the DS1820's 9 bytes of RAM data
pairmand 3:8f2b7f4940b5 309 // into the objects RAM array. Functions that use
pairmand 3:8f2b7f4940b5 310 // RAM values will automaticly call this procedure.
pairmand 3:8f2b7f4940b5 311 int i;
pairmand 3:8f2b7f4940b5 312 match_ROM(); // Select this device
pairmand 3:8f2b7f4940b5 313 onewire_byte_out( 0xBE); //Read Scratchpad command
pairmand 3:8f2b7f4940b5 314 for(i=0;i<9;i++) {
pairmand 3:8f2b7f4940b5 315 RAM[i] = onewire_byte_in();
pairmand 3:8f2b7f4940b5 316 }
pairmand 3:8f2b7f4940b5 317 // if (!RAM_checksum_error())
pairmand 3:8f2b7f4940b5 318 // crcerr = 1;
pairmand 3:8f2b7f4940b5 319 }
pairmand 3:8f2b7f4940b5 320
Sissors 5:2cd4928e8147 321 bool DS1820::setResolution(unsigned int resolution) {
pairmand 3:8f2b7f4940b5 322 bool answer = false;
pairmand 3:8f2b7f4940b5 323 resolution = resolution - 9;
pairmand 3:8f2b7f4940b5 324 if (resolution < 4) {
pairmand 3:8f2b7f4940b5 325 resolution = resolution<<5; // align the bits
pairmand 3:8f2b7f4940b5 326 RAM[4] = (RAM[4] & 0x60) | resolution; // mask out old data, insert new
pairmand 3:8f2b7f4940b5 327 write_scratchpad ((RAM[2]<<8) + RAM[3]);
pairmand 3:8f2b7f4940b5 328 // store_scratchpad (DS1820::this_device); // Need to test if this is required
pairmand 3:8f2b7f4940b5 329 answer = true;
pairmand 3:8f2b7f4940b5 330 }
pairmand 3:8f2b7f4940b5 331 return answer;
pairmand 3:8f2b7f4940b5 332 }
pairmand 3:8f2b7f4940b5 333
pairmand 3:8f2b7f4940b5 334 void DS1820::write_scratchpad(int data) {
pairmand 3:8f2b7f4940b5 335 RAM[3] = data;
pairmand 3:8f2b7f4940b5 336 RAM[2] = data>>8;
pairmand 3:8f2b7f4940b5 337 match_ROM();
pairmand 3:8f2b7f4940b5 338 onewire_byte_out(0x4E); // Copy scratchpad into DS1820 ram memory
pairmand 3:8f2b7f4940b5 339 onewire_byte_out(RAM[2]); // T(H)
pairmand 3:8f2b7f4940b5 340 onewire_byte_out(RAM[3]); // T(L)
Sissors 5:2cd4928e8147 341 if ((FAMILY_CODE == FAMILY_CODE_DS18B20 ) || (FAMILY_CODE == FAMILY_CODE_DS1822 )) {
pairmand 3:8f2b7f4940b5 342 onewire_byte_out(RAM[4]); // Configuration register
pairmand 3:8f2b7f4940b5 343 }
pairmand 3:8f2b7f4940b5 344 }
pairmand 3:8f2b7f4940b5 345
pairmand 3:8f2b7f4940b5 346 float DS1820::temperature(char scale) {
pairmand 3:8f2b7f4940b5 347 // The data specs state that count_per_degree should be 0x10 (16), I found my devices
pairmand 3:8f2b7f4940b5 348 // to have a count_per_degree of 0x4B (75). With the standard resolution of 1/2 deg C
pairmand 3:8f2b7f4940b5 349 // this allowed an expanded resolution of 1/150th of a deg C. I wouldn't rely on this
pairmand 3:8f2b7f4940b5 350 // being super acurate, but it does allow for a smooth display in the 1/10ths of a
pairmand 3:8f2b7f4940b5 351 // deg C or F scales.
pairmand 3:8f2b7f4940b5 352 float answer, remaining_count, count_per_degree;
pairmand 3:8f2b7f4940b5 353 int reading;
pairmand 3:8f2b7f4940b5 354 read_RAM();
pairmand 3:8f2b7f4940b5 355 if (RAM_checksum_error())
pairmand 3:8f2b7f4940b5 356 // Indicate we got a CRC error
Sissors 7:58b61681818f 357 answer = invalid_conversion;
pairmand 3:8f2b7f4940b5 358 else {
pairmand 3:8f2b7f4940b5 359 reading = (RAM[1] << 8) + RAM[0];
pairmand 3:8f2b7f4940b5 360 if (reading & 0x8000) { // negative degrees C
pairmand 3:8f2b7f4940b5 361 reading = 0-((reading ^ 0xffff) + 1); // 2's comp then convert to signed int
pairmand 3:8f2b7f4940b5 362 }
pairmand 3:8f2b7f4940b5 363 answer = reading +0.0; // convert to floating point
Sissors 5:2cd4928e8147 364 if ((FAMILY_CODE == FAMILY_CODE_DS18B20 ) || (FAMILY_CODE == FAMILY_CODE_DS1822 )) {
Sissors 11:1a3c3002b50c 365 answer = answer / 16.0f;
pairmand 3:8f2b7f4940b5 366 }
pairmand 3:8f2b7f4940b5 367 else {
pairmand 3:8f2b7f4940b5 368 remaining_count = RAM[6];
pairmand 3:8f2b7f4940b5 369 count_per_degree = RAM[7];
Sissors 11:1a3c3002b50c 370 answer = floor(answer/2.0f) - 0.25f + (count_per_degree - remaining_count) / count_per_degree;
pairmand 3:8f2b7f4940b5 371 }
florian 10:d297ce9ce422 372 if (scale=='F' or scale=='f')
pairmand 3:8f2b7f4940b5 373 // Convert to deg F
Sissors 11:1a3c3002b50c 374 answer = answer * 9.0f / 5.0f + 32.0f;
pairmand 3:8f2b7f4940b5 375 }
pairmand 3:8f2b7f4940b5 376 return answer;
pairmand 3:8f2b7f4940b5 377 }
pairmand 3:8f2b7f4940b5 378
pairmand 3:8f2b7f4940b5 379