Dallas' DS1820 family temperature sensor using mbed debug logs.
Fork of DS1820 by
DS1820.cpp
- Committer:
- Lucian Corduneanu
- Date:
- 2018-05-02
- Revision:
- 17:325cd3a6cbbb
- Parent:
- 16:0764e4de41d2
File content as of revision 17:325cd3a6cbbb:
/* * 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 "mbed.h" #include "DS1820.h" Serial serial(USBTX, USBRX); int main() { serial.baud(115200); DS1820 ds1820(PB_2); // substitute PB_2 with actual mbed pin name connected to the DS1820 data pin. if(ds1820.begin()) { ds1820.startConversion(); // start temperature conversion wait(2.0); // let DS1820 complete the temperature conversion while(1) { float temp = 0.0; ds1820.read(temp); serial.printf("temp = %3.1f\r\n", temp); // 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"); } */ #include "DS1820.h" /** * @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)) { debug_if(DEBUG, "No addresses.\r\n"); oneWire.reset_search(); wait_ms(250); return false; } debug_if(DEBUG, "ROM ="); for (uint8_t i = 0; i < 8; i++) { debug_if(DEBUG, " %x", addr[i]); } debug_if(DEBUG, "\r\n"); if (OneWire::crc8(addr, 7) == addr[7]) { present = true; // the first ROM byte indicates which chip switch (addr[0]) { case 0x10: model_s = true; debug_if(DEBUG, "DS18S20 or old DS1820\r\n"); break; case 0x28: model_s = false; debug_if(DEBUG, "DS18B20\r\n"); break; case 0x22: model_s = false; debug_if(DEBUG, "DS1822\r\n"); break; default: present = false; debug_if(DEBUG, "Device doesn't belong to the DS1820 family\r\n"); return false; } return true; } else { 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 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) { uint16_t temp_uint16 = 0; uint8_t result = readRaw(temp_uint16); bool temp_available = 0 == result; if (temp_available) { debug_if(DEBUG, "raw uint16 = 0x%02X \r\n", temp_uint16); // Convert to floating point value temp = toFloat(temp_uint16); } } /** * @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 uint16_t) * @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::readRaw(uint16_t &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]); debug_if(DEBUG, "raw = %#x\r\n", *p_word); 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 = *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); }