Marco Zecchini
Working version for L-tek FF1705
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DS1820.cpp
00001 /* 00002 * Dallas' DS1820 family temperature sensor. 00003 * This library depends on the OneWire library (Dallas' 1-Wire bus protocol implementation) 00004 * available at <http://developer.mbed.org/users/hudakz/code/OneWire/> 00005 * 00006 * Example of use: 00007 * 00008 * Single sensor. 00009 * 00010 * #include "mbed.h" 00011 * #include "DS1820.h" 00012 * 00013 * Serial pc(USBTX, USBRX); 00014 * DigitalOut led(LED1); 00015 * OneWire oneWire(D8); // substitute D8 with actual mbed pin name connected 1-wire bus 00016 * float temp = 0; 00017 * int result = 0; 00018 * 00019 * int main() 00020 * { 00021 * pc.printf("\r\n--Starting--\r\n"); 00022 * if (ds1820.begin()) { 00023 * while (1) { 00024 * ds1820.startConversion(); // start temperature conversion from analog to digital 00025 * wait(1.0); // let DS1820 complete the temperature conversion 00026 * result = ds1820.read(temp); // read temperature from DS1820 and perform cyclic redundancy check (CRC) 00027 * switch (result) { 00028 * case 0: // no errors -> 'temp' contains the value of measured temperature 00029 * pc.printf("temp = %3.1f%cC\r\n", temp, 176); 00030 * break; 00031 * 00032 * case 1: // no sensor present -> 'temp' is not updated 00033 * pc.printf("no sensor present\n\r"); 00034 * break; 00035 * 00036 * case 2: // CRC error -> 'temp' is not updated 00037 * pc.printf("CRC error\r\n"); 00038 * } 00039 * 00040 * led = !led; 00041 * } 00042 * } 00043 * else 00044 * pc.printf("No DS1820 sensor found!\r\n"); 00045 * } 00046 * 00047 * 00048 * More sensors connected to the same 1-wire bus. 00049 * 00050 * #include "mbed.h" 00051 * #include "DS1820.h" 00052 * 00053 * #define SENSORS_COUNT 64 // number of DS1820 sensors to be connected to the 1-wire bus (max 256) 00054 * 00055 * Serial pc(USBTX, USBRX); 00056 * DigitalOut led(LED1); 00057 * OneWire oneWire(D8); // substitute D8 with actual mbed pin name connected to the DS1820 data pin 00058 * DS1820* ds1820[SENSORS_COUNT]; 00059 * int sensors_found = 0; // counts the actually found DS1820 sensors 00060 * float temp = 0; 00061 * int result = 0; 00062 * 00063 * int main() { 00064 * int i = 0; 00065 * 00066 * pc.printf("\r\n Starting \r\n"); 00067 * //Enumerate (i.e. detect) DS1820 sensors on the 1-wire bus 00068 * for(i = 0; i < SENSORS_COUNT; i++) { 00069 * ds1820[i] = new DS1820(&oneWire); 00070 * if(!ds1820[i]->begin()) { 00071 * delete ds1820[i]; 00072 * break; 00073 * } 00074 * } 00075 * 00076 * sensors_found = i; 00077 * 00078 * if (sensors_found == 0) { 00079 * pc.printf("No DS1820 sensor found!\r\n"); 00080 * return -1; 00081 * } 00082 * else 00083 * pc.printf("Found %d sensors.\r\n", sensors_found); 00084 * 00085 * while(1) { 00086 * pc.printf("-------------------\r\n"); 00087 * for(i = 0; i < sensors_found; i++) 00088 * ds1820[i]->startConversion(); // start temperature conversion from analog to digital 00089 * wait(1.0); // let DS1820s complete the temperature conversion 00090 * for(int i = 0; i < sensors_found; i++) { 00091 * if(ds1820[i]->isPresent()) 00092 * pc.printf("temp[%d] = %3.1f%cC\r\n", i, ds1820[i]->read(), 176); // read temperature 00093 * } 00094 * } 00095 * } 00096 * 00097 */ 00098 00099 #include "DS1820.h" 00100 00101 #define DEBUG 0 00102 00103 //* Initializing static members 00104 uint8_t DS1820::lastAddr[8] = {0, 0, 0, 0, 0, 0, 0, 0}; 00105 /** 00106 * @brief Constructs a generic DS1820 sensor 00107 * @note begin() must be called to detect and initialize the actual model 00108 * @param pin: Name of data pin 00109 * @retval 00110 */ 00111 DS1820::DS1820(PinName pin) { 00112 oneWire = new OneWire(pin); 00113 present = false; 00114 model_s = false; 00115 } 00116 00117 /** 00118 * @brief Constructs a generic DS1820 sensor 00119 * @note begin() must be called to detect and initialize the actual model 00120 * @param pin: Name of data pin 00121 * @retval 00122 */ 00123 DS1820::DS1820(OneWire* wire) : 00124 oneWire(wire) { 00125 present = false; 00126 model_s = false; 00127 } 00128 00129 /** 00130 * @brief Detects and initializes the actual DS1820 model 00131 * @note 00132 * @param 00133 * @retval true: if a DS1820 family sensor was detected and initialized 00134 false: otherwise 00135 */ 00136 bool DS1820::begin(void) { 00137 #if DEBUG 00138 printf("lastAddr ="); 00139 for(uint8_t i = 0; i < 8; i++) { 00140 printf(" %x", lastAddr[i]); 00141 } 00142 printf("\r\n"); 00143 #endif 00144 if(!oneWire->search(lastAddr)) { 00145 #if DEBUG 00146 printf("No addresses.\r\n"); 00147 #endif 00148 oneWire->reset_search(); 00149 wait_ms(250); 00150 return false; 00151 } 00152 00153 for (int i = 0; i < 8; i++) 00154 addr[i] = lastAddr[i]; 00155 00156 #if DEBUG 00157 printf("ROM ="); 00158 for(uint8_t i = 0; i < 8; i++) { 00159 printf(" %x", addr[i]); 00160 } 00161 printf("\r\n"); 00162 #endif 00163 00164 if(OneWire::crc8(addr, 7) == addr[7]) { 00165 present = true; 00166 00167 // the first ROM byte indicates which chip 00168 switch(addr[0]) { 00169 case 0x10: 00170 model_s = true; 00171 #if DEBUG 00172 printf("DS18S20 or old DS1820\r\n"); 00173 #endif 00174 break; 00175 00176 case 0x28: 00177 model_s = false; 00178 #if DEBUG 00179 printf("DS18B20\r\n"); 00180 #endif 00181 break; 00182 00183 case 0x22: 00184 model_s = false; 00185 #if DEBUG 00186 printf("DS1822\r\n"); 00187 #endif 00188 break; 00189 00190 default: 00191 present = false; 00192 #if DEBUG 00193 printf("Device doesn't belong to the DS1820 family\r\n"); 00194 #endif 00195 return false; 00196 } 00197 return true; 00198 } 00199 else { 00200 #if DEBUG 00201 printf("Invalid CRC!\r\n"); 00202 #endif 00203 return false; 00204 } 00205 } 00206 00207 /** 00208 * @brief Informs about presence of a DS1820 sensor. 00209 * @note begin() shall be called before using this function 00210 * if a generic DS1820 instance was created by the user. 00211 * No need to call begin() for a specific DS1820 instance. 00212 * @param 00213 * @retval true: when a DS1820 sensor is present 00214 * false: otherwise 00215 */ 00216 bool DS1820::isPresent(void) { 00217 return present; 00218 } 00219 00220 /** 00221 * @brief Sets temperature-to-digital conversion resolution. 00222 * @note The configuration register allows the user to set the resolution 00223 * of the temperature-to-digital conversion to 9, 10, 11, or 12 bits. 00224 * Defaults to 12-bit resolution for DS18B20. 00225 * DS18S20 allows only 9-bit resolution. 00226 * @param res: Resolution of the temperature-to-digital conversion in bits. 00227 * @retval 00228 */ 00229 void DS1820::setResolution(uint8_t res) { 00230 // keep resolution within limits 00231 if(res > 12) 00232 res = 12; 00233 if(res < 9) 00234 res = 9; 00235 if(model_s) 00236 res = 9; 00237 00238 oneWire->reset(); 00239 oneWire->select(addr); 00240 oneWire->write_byte(0xBE); // to read Scratchpad 00241 for(uint8_t i = 0; i < 9; i++) // read Scratchpad bytes 00242 data[i] = oneWire->read_byte(); 00243 00244 data[4] |= (res - 9) << 5; // update configuration byte (set resolution) 00245 oneWire->reset(); 00246 oneWire->select(addr); 00247 oneWire->write_byte(0x4E); // to write into Scratchpad 00248 for(uint8_t i = 2; i < 5; i++) // write three bytes (2nd, 3rd, 4th) into Scratchpad 00249 oneWire->write_byte(data[i]); 00250 } 00251 00252 /** 00253 * @brief Starts temperature conversion 00254 * @note The time to complete the converion depends on the selected resolution: 00255 * 9-bit resolution -> max conversion time = 93.75ms 00256 * 10-bit resolution -> max conversion time = 187.5ms 00257 * 11-bit resolution -> max conversion time = 375ms 00258 * 12-bit resolution -> max conversion time = 750ms 00259 * @param 00260 * @retval 00261 */ 00262 void DS1820::startConversion(void) { 00263 if(present) { 00264 oneWire->reset(); 00265 oneWire->select(addr); 00266 oneWire->write_byte(0x44); //start temperature conversion 00267 } 00268 } 00269 00270 /** 00271 * @brief Reads temperature from the chip's Scratchpad 00272 * @note 00273 * @param 00274 * @retval Floating point temperature value 00275 */ 00276 float DS1820::read(void) { 00277 if(present) { 00278 oneWire->reset(); 00279 oneWire->select(addr); 00280 oneWire->write_byte(0xBE); // to read Scratchpad 00281 for(uint8_t i = 0; i < 9; i++) // reading scratchpad registers 00282 data[i] = oneWire->read_byte(); 00283 00284 // Convert the raw bytes to a 16-bit unsigned value 00285 uint16_t* p_word = reinterpret_cast < uint16_t * > (&data[0]); 00286 00287 #if DEBUG 00288 printf("raw = %#x\r\n", *p_word); 00289 #endif 00290 00291 if(model_s) { 00292 *p_word = *p_word << 3; // 9-bit resolution 00293 if(data[7] == 0x10) { 00294 00295 // "count remain" gives full 12-bit resolution 00296 *p_word = (*p_word & 0xFFF0) + 12 - data[6]; 00297 } 00298 } 00299 else { 00300 uint8_t cfg = (data[4] & 0x60); // default 12-bit resolution 00301 00302 // at lower resolution, the low bits are undefined, so let's clear them 00303 if(cfg == 0x00) 00304 *p_word = *p_word &~7; // 9-bit resolution 00305 else 00306 if(cfg == 0x20) 00307 *p_word = *p_word &~3; // 10-bit resolution 00308 else 00309 if(cfg == 0x40) 00310 *p_word = *p_word &~1; // 11-bit resolution 00311 00312 } 00313 00314 // Convert the raw bytes to a 16-bit signed fixed point value : 00315 // 1 sign bit, 7 integer bits, 8 fractional bits (two’s compliment 00316 // and the LSB of the 16-bit binary number represents 1/256th of a unit). 00317 *p_word = *p_word << 4; 00318 00319 // Convert to floating point value 00320 return(toFloat(*p_word)); 00321 } 00322 else 00323 return 0; 00324 } 00325 00326 /** 00327 * @brief Reads temperature from chip's scratchpad. 00328 * @note Verifies data integrity by calculating cyclic redundancy check (CRC). 00329 * If the calculated CRC dosn't match the one stored in chip's scratchpad register 00330 * the temperature variable is not updated and CRC error code is returned. 00331 * @param temp: The temperature variable to be updated by this routine. 00332 * (It's passed as reference to floating point.) 00333 * @retval error code: 00334 * 0 - no errors ('temp' contains the temperature measured) 00335 * 1 - sensor not present ('temp' is not updated) 00336 * 2 - CRC error ('temp' is not updated) 00337 */ 00338 uint8_t DS1820::read(float& temp) { 00339 if(present) { 00340 oneWire->reset(); 00341 oneWire->select(addr); 00342 oneWire->write_byte(0xBE); // to read Scratchpad 00343 for(uint8_t i = 0; i < 9; i++) // reading scratchpad registers 00344 data[i] = oneWire->read_byte(); 00345 00346 if(oneWire->crc8(data, 8) != data[8]) // if calculated CRC does not match the stored one 00347 { 00348 #if DEBUG 00349 for(uint8_t i = 0; i < 9; i++) 00350 printf("data[%d]=0x%.2x\r\n", i, data[i]); 00351 #endif 00352 return 2; // return with CRC error 00353 } 00354 00355 // Convert the raw bytes to a 16bit unsigned value 00356 uint16_t* p_word = reinterpret_cast < uint16_t * > (&data[0]); 00357 00358 #if DEBUG 00359 printf("raw = %#x\r\n", *p_word); 00360 #endif 00361 00362 if(model_s) { 00363 *p_word = *p_word << 3; // 9 bit resolution, max conversion time = 750ms 00364 if(data[7] == 0x10) { 00365 00366 // "count remain" gives full 12 bit resolution 00367 *p_word = (*p_word & 0xFFF0) + 12 - data[6]; 00368 } 00369 00370 // Convert the raw bytes to a 16bit signed fixed point value : 00371 // 1 sign bit, 7 integer bits, 8 fractional bits (two's compliment 00372 // and the LSB of the 16bit binary number represents 1/256th of a unit). 00373 *p_word = *p_word << 4; 00374 // Convert to floating point value 00375 temp = toFloat(*p_word); 00376 return 0; // return with no errors 00377 } 00378 else { 00379 uint8_t cfg = (data[4] & 0x60); // default 12bit resolution, max conversion time = 750ms 00380 00381 // at lower resolution, the low bits are undefined, so let's clear them 00382 if(cfg == 0x00) 00383 *p_word = *p_word &~7; // 9bit resolution, max conversion time = 93.75ms 00384 else 00385 if(cfg == 0x20) 00386 *p_word = *p_word &~3; // 10bit resolution, max conversion time = 187.5ms 00387 else 00388 if(cfg == 0x40) 00389 *p_word = *p_word &~1; // 11bit resolution, max conversion time = 375ms 00390 00391 // Convert the raw bytes to a 16bit signed fixed point value : 00392 // 1 sign bit, 7 integer bits, 8 fractional bits (two's complement 00393 // and the LSB of the 16bit binary number represents 1/256th of a unit). 00394 *p_word = *p_word << 4; 00395 // Convert to floating point value 00396 temp = toFloat(*p_word); 00397 return 0; // return with no errors 00398 } 00399 } 00400 else 00401 return 1; // error, sensor is not present 00402 } 00403 00404 /** 00405 * @brief Converts a 16-bit signed fixed point value to floating point value 00406 * @note The 16-bit unsigned integer represnts actually 00407 * a 16-bit signed fixed point value: 00408 * 1 sign bit, 7 integer bits, 8 fractional bits (two’s complement 00409 * and the LSB of the 16-bit binary number represents 1/256th of a unit). 00410 * @param 16-bit unsigned integer 00411 * @retval Floating point value 00412 */ 00413 float DS1820::toFloat(uint16_t word) { 00414 if(word & 0x8000) 00415 return (-float(uint16_t(~word + 1)) / 256.0f); 00416 else 00417 return (float(word) / 256.0f); 00418 } 00419
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