sad
Dependencies: OneWire
DS1820.cpp
- Committer:
- hudakz
- Date:
- 2015-03-19
- Revision:
- 3:a250babd0a9f
- Parent:
- 2:b7ad1da7331a
- Child:
- 4:adf4e7972d73
File content as of revision 3:a250babd0a9f:
/* * Dallas' DS1820 family temperature sensor. * This library depends on the OneWire library (Dallas' 1-Wire bus protocol implementation) * which is available at <http://developer.mbed.org/users/hudakz/code/OneWire/> * * Example of use: * * #include "DS1820.h" * * int main() { * DS1820 ds1820(PA_9); * * if(ds1820.begin()) { * ds1820.startConversion(); * wait(1.0); * while(1) { * serial.printf("temp = %3.1f\r\n", ds1820.read()); * ds1820.startConversion(); * wait(1.0); * } * } else * serial.printf("No DS1820 sensor found!\r\n"); * } */ #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 = 0; type_s = 0; } /** * @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 = 1; type_s = 1; } else if((model == 'B') or (model == 'b')) { present = 1; type_s = 0; } else present = 0; } /** * @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 = 1; // the first ROM byte indicates which chip switch(addr[0]) { case 0x10: type_s = 1; #if DEBUG serial.printf("DS18S20 or old DS1820\r\n"); #endif break; case 0x28: type_s = 0; #if DEBUG serial.printf("DS18B20\r\n"); #endif break; case 0x22: type_s = 0; #if DEBUG serial.printf("DS1822\r\n"); #endif break; default: present = 0; #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 Starts temperature conversion * @note The time to complete the converion depends on the selected resolusion * @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++) data[i] = oneWire.read(); // Convert the raw bytes to a 16bit signed fixed point value : // 1 sign bit, 7 integer bits, 8 fractional bits (two’s compliment // ie. the LSB of the 16bit binary number represents 1/256th of a unit). // Finally the 16bit signed fixed point value is converted // to floating point value by calling the toFloat(value) function. uint16_t* p_word = reinterpret_cast < uint16_t * > (&data[0]); #if DEBUG serial.printf("raw = %#x\r\n", *p_word); #endif if(type_s) { *p_word = *p_word << 3; // default 9 bit resolution if(data[7] == 0x10) { // "count remain" gives full 12 bit resolution *p_word = (*p_word & 0xFFF0) + 12 - data[6]; } *p_word = *p_word << 4; return(toFloat(*p_word)); } else { uint8_t cfg = (data[4] & 0x60); // at lower res, the low bits are undefined, so let's zero them if(cfg == 0x00) *p_word = *p_word &~7; // 9 bit resolution, 93.75 ms else if(cfg == 0x20) *p_word = *p_word &~3; // 10 bit res, 187.5 ms else if(cfg == 0x40) *p_word = *p_word &~1; // 11 bit res, 375 ms *p_word = *p_word << 4; // default is 12 bit resolution return(toFloat(*p_word)); } } else return 0; } /** * @brief Converts a 16bit signed fixed point value to floating point value * @note The 16bit unsigned integer represnts actually * a 16bit signed fixed point value: * 1 sign bit, 7 integer bits, 8 fractional bits * (two’s compliment ie. the LSB of the 16bit binary number * represents 1/256th of a unit). * @param 16bit unsigned integer * @retval Floating point temperature value */ float DS1820::toFloat(uint16_t word) { if(word & 0x8000) return (-float(uint16_t(~word + 1)) / 256.0f); else return (float(word) / 256.0f); }