Working version for L-tek FF1705
Diff: DS1820.cpp
- Revision:
- 6:518950e436be
- Parent:
- 4:adf4e7972d73
- Child:
- 8:8dfdd1603e4d
diff -r 4b076ea3f3ba -r 518950e436be DS1820.cpp --- a/DS1820.cpp Sun Mar 22 08:47:07 2015 +0000 +++ b/DS1820.cpp Thu Mar 26 17:36:56 2015 +0000 @@ -1,26 +1,33 @@ /* * 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/> + * 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); + * 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()); - * ds1820.startConversion(); - * wait(1.0); + * 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" @@ -135,12 +142,12 @@ } /** - * @brief Sets temperature-to-digital conversion resolution + * @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 12bit resolution for DS18B20. - * DS18S20 allows only 9bit resolution. - * @param res: Resolution of the temperature-to-digital conversion in bits + * 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) { @@ -156,7 +163,7 @@ oneWire.skip(); oneWire.write(0xBE); // to read Scratchpad for(uint8_t i = 0; i < 9; i++) // read Scratchpad bytes - data[i] = oneWire.read(); + data[i] = oneWire.read(); data[4] |= (res - 9) << 5; // update configuration byte (set resolution) oneWire.reset(); @@ -169,7 +176,11 @@ /** * @brief Starts temperature conversion - * @note The time to complete the converion depends on the selected resolusion + * @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 */ @@ -182,7 +193,7 @@ } /** - * @brief Reads temperature from the chip's scratchpad + * @brief Reads temperature from the chip's Scratchpad * @note * @param * @retval Floating point temperature value @@ -192,10 +203,10 @@ oneWire.reset(); oneWire.skip(); oneWire.write(0xBE); // to read Scratchpad - for(uint8_t i = 0; i < 9; i++) - data[i] = oneWire.read(); + for(uint8_t i = 0; i < 9; i++) // read Scratchpad bytes + data[i] = oneWire.read(); - // Convert the raw bytes to a 16bit unsigned value + // Convert the raw bytes to a 16-bit unsigned value uint16_t* p_word = reinterpret_cast < uint16_t * > (&data[0]); #if DEBUG @@ -203,52 +214,47 @@ #endif if(type_s) { - *p_word = *p_word << 3; // 9 bit resolution, max conversion time = 750ms + *p_word = *p_word << 3; // 9-bit resolution if(data[7] == 0x10) { - // "count remain" gives full 12 bit resolution + // "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 - return(toFloat(*p_word)); } else { - uint8_t cfg = (data[4] & 0x60); // default 12bit resolution, max conversion time = 750ms + 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; // 9bit resolution, max conversion time = 93.75ms + *p_word = *p_word &~7; // 9-bit resolution else if(cfg == 0x20) - *p_word = *p_word &~3; // 10bit resolution, max conversion time = 187.5ms + *p_word = *p_word &~3; // 10-bit resolution else if(cfg == 0x40) - *p_word = *p_word &~1; // 11bit resolution, max conversion time = 375ms + *p_word = *p_word &~1; // 11-bit resolution - // 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 - return(toFloat(*p_word)); } + + // 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 Converts a 16bit signed fixed point value to floating point value - * @note The 16bit unsigned integer represnts actually - * a 16bit signed fixed point value: + * @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 16bit binary number represents 1/256th of a unit). - * @param 16bit unsigned integer + * 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) {