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Diff: OneWireThermometer.cpp
- Revision:
- 0:2f78e3dca55d
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/OneWireThermometer.cpp Mon Oct 17 10:42:00 2011 +0000 @@ -0,0 +1,167 @@ +/* +* 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; +} \ No newline at end of file