![](/media/cache/img/default_profile.jpg.50x50_q85.jpg)
OneWireThermometer.cpp
- Committer:
- gbeardall
- Date:
- 2011-10-17
- Revision:
- 0:2f78e3dca55d
File content as of revision 0:2f78e3dca55d:
/* * OneWireThermometer. Base class for Maxim One-Wire Thermometers. * 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 "OneWireThermometer.h" #include "OneWireDefs.h" #include "DebugTrace.h" DebugTrace pc(ON, TO_SERIAL); // constructor specifies standard speed for the 1-Wire comms OneWireThermometer::OneWireThermometer(bool crcOn, bool useAddr, bool parasitic, PinName pin, int device_id) : useCRC(crcOn), useAddress(useAddr), useParasiticPower(parasitic), oneWire(pin, STANDARD), deviceId(device_id), resolution(twelveBit) { // NOTE: the power-up resolution of a DS18B20 is 12 bits. The DS18S20's resolution is always // 9 bits + enhancement, but we treat the DS18S20 as fixed to 12 bits for calculating the // conversion time Tconv. } bool OneWireThermometer::initialize() { // get the device address for use in selectROM() when reading the temperature // - not really needed except for device validation if using skipROM() if (useAddress) { pc.traceOut("\r\n"); pc.traceOut("New Scan\r\n"); oneWire.resetSearch(); if (!oneWire.search(address)) // search for 1-wire device address { pc.traceOut("No more addresses.\r\n"); wait(2); return false; } pc.traceOut("Address = "); for (int i = 0; i < ADDRESS_SIZE; i++) { pc.traceOut("%x ", (int)address[i]); } pc.traceOut("\r\n"); if (OneWireCRC::crc8(address, ADDRESS_CRC_BYTE) != address[ADDRESS_CRC_BYTE]) // check address CRC is valid { pc.traceOut("CRC is not valid!\r\n"); wait(2); return false; } if (address[0] != deviceId) { // Make sure it is a one-wire thermometer device if (DS18B20_ID == deviceId) pc.traceOut("You need to use a DS1820 or DS18S20 for correct results.\r\n"); else if (DS18S20_ID == deviceId) pc.traceOut("You need to use a DS18B20 for correct results.\r\n"); else pc.traceOut("Device is not a DS18B20/DS1820/DS18S20 device.\r\n"); wait(2); return false; } else { if (DS18B20_ID == deviceId) pc.traceOut("DS18B20 present and correct.\r\n"); if (DS18S20_ID == deviceId) pc.traceOut("DS1820/DS18S20 present and correct.\r\n"); } } return true; } // NOTE ON USING SKIP ROM: ok to use before a Convert command to get all // devices on the bus to do simultaneous temperature conversions. BUT can // only use before a Read Scratchpad command if there is only one device on the // bus. For purpose of this library it is assumed there is only one device // on the bus. void OneWireThermometer::resetAndAddress() { oneWire.reset(); // reset device if (useAddress) { oneWire.matchROM(address); // select which device to talk to } else { oneWire.skipROM(); // broadcast } } bool OneWireThermometer::readAndValidateData(BYTE* data) { bool dataOk = true; resetAndAddress(); oneWire.writeByte(READSCRATCH); // read Scratchpad pc.traceOut("read = "); for (int i = 0; i < THERMOM_SCRATCHPAD_SIZE; i++) { // we need all bytes which includes CRC check byte data[i] = oneWire.readByte(); pc.traceOut("%x ", (int)data[i]); } pc.traceOut("\r\n"); // Check CRC is valid if you want to if (useCRC && !(OneWireCRC::crc8(data, THERMOM_CRC_BYTE) == data[THERMOM_CRC_BYTE])) { // CRC failed pc.traceOut("CRC FAILED... \r\n"); dataOk = false; } return dataOk; } float OneWireThermometer::readTemperature() { BYTE data[THERMOM_SCRATCHPAD_SIZE]; float realTemp = -999; resetAndAddress(); oneWire.writeByte(CONVERT); // issue Convert command if (useParasiticPower) { // wait while converting - Tconv (according to resolution of reading) wait_ms(CONVERSION_TIME[resolution]); } else { // TODO // after the Convert command, the device should respond by transmitting 0 // while the temperature conversion is in progress and 1 when the conversion is done // - as were are not checking this (TODO), we use Tconv, as we would do for // parasitic power wait_ms(CONVERSION_TIME[resolution]); } if (readAndValidateData(data)) // issue Read Scratchpad commmand and get data { realTemp = calculateTemperature(data); } return realTemp; }