Diff: OneWireThermometer.cpp

Revision:

0:21c0c97a5d7c

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/OneWireThermometer.cpp	Thu Feb 03 12:10:20 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; 
+}
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