sad
Dependencies: OneWire
DS1820.cpp
- Committer:
- hudakz
- Date:
- 2015-10-28
- Revision:
- 13:b593a82ce790
- Parent:
- 8:8dfdd1603e4d
- Child:
- 14:b02fa18b294a
File content as of revision 13:b593a82ce790:
/* * Dallas' DS1820 family temperature sensor. * This library depends on the OneWire library (Dallas' 1-Wire bus protocol implementation) * available at <http://developer.mbed.org/users/hudakz/code/OneWire/> * * Example of use: * * #include "DS1820.h" * * Serial serial(USBTX, USBRX); * * int main() { * DS1820 ds1820(PA_9); // substitute PA_9 with actual mbed pin name connected to the DS1820 data pin * * if(ds1820.begin()) { * ds1820.startConversion(); * wait(1.0); * while(1) { * serial.printf("temp = %3.1f\r\n", ds1820.read()); // read temperature * ds1820.startConversion(); // start temperature conversion * wait(1.0); // let DS1820 complete the temperature conversion * } * } else * serial.printf("No DS1820 sensor found!\r\n"); * } * * * Note: Don't forget to connect a 4.7k Ohm resistor * between the DS1820's data pin and the +3.3V pin * */ #include "DS1820.h" #define DEBUG 0 #if DEBUG extern Serial serial; #endif /** * @brief Constructs a generic DS1820 sensor * @note begin() must be called to detect and initialize the actual model * @param pin: Name of data pin * @retval */ DS1820::DS1820(PinName pin) : oneWire(pin) { present = false; model_s = false; } /** * @brief Constructs a specific model * @note No need to call begin() to detect and initialize the model * @param model: One character model name: 'S', 's', 'B' or 'b' * pin: Name of data pin * @retval */ DS1820::DS1820(char model, PinName pin) : oneWire(pin) { if((model == 'S') or (model == 's')) { present = true; model_s = true; } else if((model == 'B') or (model == 'b')) { present = true; model_s = false; } else present = false; } /** * @brief Detects and initializes the actual DS1820 model * @note * @param * @retval true: if a DS1820 family sensor was detected and initialized false: otherwise */ bool DS1820::begin(void) { oneWire.reset_search(); wait_ms(250); if(!oneWire.search(addr)) { #if DEBUG serial.printf("No addresses.\r\n"); #endif oneWire.reset_search(); wait_ms(250); return false; } #if DEBUG serial.printf("ROM ="); for(uint8_t i = 0; i < 8; i++) { serial.printf(" %x", addr[i]); } serial.printf("\r\n"); #endif if(OneWire::crc8(addr, 7) == addr[7]) { present = true; // the first ROM byte indicates which chip switch(addr[0]) { case 0x10: model_s = true; #if DEBUG serial.printf("DS18S20 or old DS1820\r\n"); #endif break; case 0x28: model_s = false; #if DEBUG serial.printf("DS18B20\r\n"); #endif break; case 0x22: model_s = false; #if DEBUG serial.printf("DS1822\r\n"); #endif break; default: present = false; #if DEBUG serial.printf("Device doesn't belong to the DS1820 family\r\n"); #endif return false; } return true; } else { #if DEBUG serial.printf("Invalid CRC!\r\n"); #endif return false; } } /** * @brief Informs about presence of a DS1820 sensor. * @note begin() shall be called before using this function * if a generic DS1820 instance was created by the user. * No need to call begin() for a specific DS1820 instance. * @param * @retval true: when a DS1820 sensor is present * false: otherwise */ bool DS1820::isPresent(void) { return present; } /** * @brief Sets temperature-to-digital conversion resolution. * @note The configuration register allows the user to set the resolution * of the temperature-to-digital conversion to 9, 10, 11, or 12 bits. * Defaults to 12-bit resolution for DS18B20. * DS18S20 allows only 9-bit resolution. * @param res: Resolution of the temperature-to-digital conversion in bits. * @retval */ void DS1820::setResolution(uint8_t res) { // keep resolution within limits if(res > 12) res = 12; if(res < 9) res = 9; if(model_s) res = 9; oneWire.reset(); oneWire.skip(); oneWire.write(0xBE); // to read Scratchpad for(uint8_t i = 0; i < 9; i++) // read Scratchpad bytes data[i] = oneWire.read(); data[4] |= (res - 9) << 5; // update configuration byte (set resolution) oneWire.reset(); oneWire.skip(); oneWire.write(0x4E); // to write into Scratchpad for(uint8_t i = 2; i < 5; i++) // write three bytes (2nd, 3rd, 4th) into Scratchpad oneWire.write(data[i]); } /** * @brief Starts temperature conversion * @note The time to complete the converion depends on the selected resolution: * 9-bit resolution -> max conversion time = 93.75ms * 10-bit resolution -> max conversion time = 187.5ms * 11-bit resolution -> max conversion time = 375ms * 12-bit resolution -> max conversion time = 750ms * @param * @retval */ void DS1820::startConversion(void) { if(present) { oneWire.reset(); oneWire.skip(); oneWire.write(0x44); //start temperature conversion } } /** * @brief Reads temperature from the chip's Scratchpad * @note * @param * @retval Floating point temperature value */ float DS1820::read(void) { if(present) { oneWire.reset(); oneWire.skip(); oneWire.write(0xBE); // to read Scratchpad for(uint8_t i = 0; i < 9; i++) // read Scratchpad bytes data[i] = oneWire.read(); // Convert the raw bytes to a 16-bit unsigned value uint16_t* p_word = reinterpret_cast < uint16_t * > (&data[0]); #if DEBUG serial.printf("raw = %#x\r\n", *p_word); #endif if(model_s) { *p_word = *p_word << 3; // 9-bit resolution if(data[7] == 0x10) { // "count remain" gives full 12-bit resolution *p_word = (*p_word & 0xFFF0) + 12 - data[6]; } } else { uint8_t cfg = (data[4] & 0x60); // default 12-bit resolution // at lower resolution, the low bits are undefined, so let's clear them if(cfg == 0x00) *p_word = *p_word &~7; // 9-bit resolution else if(cfg == 0x20) *p_word = *p_word &~3; // 10-bit resolution else if(cfg == 0x40) *p_word = *p_word &~1; // 11-bit resolution } // Convert the raw bytes to a 16-bit signed fixed point value : // 1 sign bit, 7 integer bits, 8 fractional bits (two’s compliment // and the LSB of the 16-bit binary number represents 1/256th of a unit). *p_word = *p_word << 4; // Convert to floating point value return(toFloat(*p_word)); } else return 0; } /** * @brief Reads temperature from chip's scratchpad. * @note Verifies data integrity by calculating cyclic redundancy check (CRC). * If the calculated CRC dosn't match the one stored in chip's scratchpad register * the temperature variable is not updated and CRC error code is returned. * @param temp: The temperature variable to be updated by this routine. * (It's passed as reference to floating point.) * @retval error code: * 0 - no errors ('temp' contains the temperature measured) * 1 - sensor not present ('temp' is not updated) * 2 - CRC error ('temp' is not updated) */ uint8_t DS1820::read(float& temp) { if(present) { oneWire.reset(); oneWire.skip(); oneWire.write(0xBE); // to read Scratchpad for(uint8_t i = 0; i < 9; i++) // reading scratchpad registers data[i] = oneWire.read(); if(oneWire.crc8(data, 8) != data[8]) // if calculated CRC does not match the stored one return 2; // return with CRC error // Convert the raw bytes to a 16bit unsigned value uint16_t* p_word = reinterpret_cast < uint16_t * > (&data[0]); #if DEBUG serial.printf("raw = %#x\r\n", *p_word); #endif if(model_s) { *p_word = *p_word << 3; // 9 bit resolution, max conversion time = 750ms if(data[7] == 0x10) { // "count remain" gives full 12 bit resolution *p_word = (*p_word & 0xFFF0) + 12 - data[6]; } // Convert the raw bytes to a 16bit signed fixed point value : // 1 sign bit, 7 integer bits, 8 fractional bits (two's compliment // and the LSB of the 16bit binary number represents 1/256th of a unit). *p_word = *p_word << 4; // Convert to floating point value temp = toFloat(*p_word); return 0; // return with no errors } else { uint8_t cfg = (data[4] & 0x60); // default 12bit resolution, max conversion time = 750ms // at lower resolution, the low bits are undefined, so let's clear them if(cfg == 0x00) *p_word = *p_word &~7; // 9bit resolution, max conversion time = 93.75ms else if(cfg == 0x20) *p_word = *p_word &~3; // 10bit resolution, max conversion time = 187.5ms else if(cfg == 0x40) *p_word = *p_word &~1; // 11bit resolution, max conversion time = 375ms // Convert the raw bytes to a 16bit signed fixed point value : // 1 sign bit, 7 integer bits, 8 fractional bits (two's compliment // and the LSB of the 16bit binary number represents 1/256th of a unit). *p_word = *p_word << 4; // Convert to floating point value temp = toFloat(*p_word); return 0; // return with no errors } } else return 1; // error, sensor is not present } /** * @brief Converts a 16-bit signed fixed point value to floating point value * @note The 16-bit unsigned integer represnts actually * a 16-bit signed fixed point value: * 1 sign bit, 7 integer bits, 8 fractional bits (two’s compliment * and the LSB of the 16-bit binary number represents 1/256th of a unit). * @param 16-bit unsigned integer * @retval Floating point value */ float DS1820::toFloat(uint16_t word) { if(word & 0x8000) return (-float(uint16_t(~word + 1)) / 256.0f); else return (float(word) / 256.0f); }