Library for Programmable Resolution 1-Wire Digital ThermometerDS18B20
Diff: DS18B20.cpp
- Revision:
- 0:21c0c97a5d7c
diff -r 000000000000 -r 21c0c97a5d7c DS18B20.cpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/DS18B20.cpp Thu Feb 03 12:10:20 2011 +0000 @@ -0,0 +1,103 @@ +/* +* DS18B20. Maxim DS18B20 One-Wire Thermometer. +* Uses the OneWireCRC library. +* +* Copyright (C) <2010> Petras Saduikis <petras@petras.co.uk> +* +* This file is part of OneWireThermometer. +* +* OneWireThermometer is free software: you can redistribute it and/or modify +* it under the terms of the GNU General Public License as published by +* the Free Software Foundation, either version 3 of the License, or +* (at your option) any later version. +* +* OneWireThermometer is distributed in the hope that it will be useful, +* but WITHOUT ANY WARRANTY; without even the implied warranty of +* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +* GNU General Public License for more details. +* +* You should have received a copy of the GNU General Public License +* along with OneWireThermometer. If not, see <http://www.gnu.org/licenses/>. +*/ + +#include "DS18B20.h" +#include "DebugTrace.h" + +DebugTrace pc_ds18B20(ON, TO_SERIAL); + +DS18B20::DS18B20(bool crcOn, bool useAddr, bool parasitic, PinName pin) : + OneWireThermometer(crcOn, useAddr, parasitic, pin, DS18B20_ID) +{ +} + +void DS18B20::setResolution(eResolution resln) +{ + // as the write to the configuration register involves a write to the + // high and low alarm bytes, need to read these registers first + // and copy them back on the write + + BYTE read_data[THERMOM_SCRATCHPAD_SIZE]; + BYTE write_data[ALARM_CONFIG_SIZE]; + + if (readAndValidateData(read_data)) + { + // copy alarm and config data to write data + for (int k = 2; k < 5; k++) + { + write_data[k - 2] = read_data[k]; + } + int config = write_data[2]; + config &= 0x9F; + config ^= (resln << 5); + write_data[2] = config; + + resetAndAddress(); + oneWire.writeByte(WRITESCRATCH); + for (int k = 0; k < 3; k++) + { + oneWire.writeByte(write_data[k]); + } + + // remember it so we can use the correct delay in reading the temperature + // for parasitic power + resolution = resln; + } +} + +float DS18B20::calculateTemperature(BYTE* data) +{ + bool signBit = false; + if (data[TEMPERATURE_MSB] & 0x80) signBit = true; + + int read_temp = (data[TEMPERATURE_MSB] << 8) + data[TEMPERATURE_LSB]; + if (signBit) + { + read_temp = (read_temp ^ 0xFFFF) + 1; // two's complement + read_temp *= -1; + } + + int resolution = (data[CONFIG_REG_BYTE] & 0x60) >> 5; // mask off bits 6,5 and move to 1,0 + switch (resolution) + { + case nineBit: // 0.5 deg C increments + read_temp &= 0xFFF8; // bits 2,1,0 are undefined + pc_ds18B20.traceOut("9 bit resolution ...\r\n"); + break; + case tenBit: // 0.25 deg C increments + read_temp &= 0xFFFC; // bits 1,0 are undefined + pc_ds18B20.traceOut("10 bit resolution ...\r\n"); + break; + case elevenBit: // 0.125 deg C increments + read_temp &= 0xFFFE; // bit 0 is undefined + pc_ds18B20.traceOut("11 bit resolution ...\r\n"); + break; + case twelveBit: // 0.0625 deg C increments + pc_ds18B20.traceOut("12 bit resolution ...\r\n"); + break; + } + float realTemp = (float)read_temp/16 ; + + pc_ds18B20.traceOut("TEMP_READ/REAL TEMP: %f \r\n", realTemp); + + return realTemp; +} \ No newline at end of file