Library for Programmable Resolution 1-Wire Digital ThermometerDS18B20
DS18B20.cpp
- Committer:
- kriedel
- Date:
- 2011-02-03
- Revision:
- 0:21c0c97a5d7c
File content as of revision 0:21c0c97a5d7c:
/* * 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; }