Adam Green / WeatherMeters

Library for interfacing to Sparkfun Weather Meters.

Dependents:   WeatherStation Deneme testgeneral ... more

WindVane.cpp@0:457832d52954, 2012-02-25 (annotated)

Committer:
AdamGreen
Date:
Sat Feb 25 03:23:51 2012 +0000
Revision:
0:457832d52954

        

        
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/* Copyright 2012 Adam Green (http://mbed.org/users/AdamGreen/)





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   Licensed under the Apache License, Version 2.0 (the "License");





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   you may not use this file except in compliance with the License.





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   You may obtain a copy of the License at





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       http://www.apache.org/licenses/LICENSE-2.0





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   Unless required by applicable law or agreed to in writing, software





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   distributed under the License is distributed on an "AS IS" BASIS,





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   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.





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   See the License for the specific language governing permissions and





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   limitations under the License.





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*/





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/* Declaration of class to interface with wind vane sensor Sparkfun Weather Meters: 





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    http://www.sparkfun.com/products/8942





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*/





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#include <mbed.h>





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#include "WindVane.h"





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#define REV_PER_SECOND_TO_KMPH  2.4f





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#define PARALLEL_R(R1, R2) (((R1) * (R2)) / ((R1) + (R2)))





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#define ARRAY_SIZE(X) (sizeof(X)/sizeof(X[0]))





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struct SDescription





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{





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    const char* DirectionString;





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    float       DirectionAngle;





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    float       SensorResistance;





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};





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static SDescription g_WindVaneDescriptionTable[16] = {





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    { "North",            0.0f,  33.0f * 1000.0f },





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    { "North North East", 22.5f, PARALLEL_R(33.0f * 1000.0f, 8.2f * 1000.0f) },





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    { "North East",       45.0f, 8.2f * 1000.0f },





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    { "East North East",  67.5f, PARALLEL_R(8.2f * 1000.0f, 1000.0f) },





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    { "East",             90.0f, 1000.0f },





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    { "East South East",  112.5f, PARALLEL_R(1000.0f, 2.2f * 1000.0f) },





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    { "South East",       135.0f, 2.2f * 1000.0f },





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    { "South South East", 157.5f, PARALLEL_R(2.2f * 1000.0f, 3.9f * 1000.0f) },





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    { "South",            180.0f, 3.9f * 1000.0f },





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    { "South South West", 202.5f, PARALLEL_R(3.9f * 1000.0f, 16.0f * 1000.0f) },





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    { "South West",       225.0f, 16.0f * 1000.0f },





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    { "West South West",  247.5f, PARALLEL_R(16.0f * 1000.0f, 120.0f * 1000.0f) },





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    { "West",             270.0f, 120.0f * 1000.0f },





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    { "West North West",  292.5f, PARALLEL_R(120.0f * 1000.0f, 64.9f * 1000.0f) },





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    { "North West",       315.0f, 64.9f * 1000.0f },





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    { "North North West", 337.5f, PARALLEL_R(64.9f * 1000.0f, 33.0f * 1000.0f) }





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};





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CWindVane::CWindVane(PinName WindVanePin, float WindVaneSeriesResistance)





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    : m_WindVaneAnalogIn(WindVanePin)





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{





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    for (size_t i = 0 ; i < ARRAY_SIZE(g_WindVaneDescriptionTable) ; i++)





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    {





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        SDescription* pDescription = &g_WindVaneDescriptionTable[i];





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        m_WindVaneVoltageTable[i] = pDescription->SensorResistance /





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                                    (pDescription->SensorResistance + WindVaneSeriesResistance);





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    }





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}





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const char* CWindVane::GetWindDirectionAsString()





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{





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    return g_WindVaneDescriptionTable[DetermineWindDirectionIndex()].DirectionString;





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}





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float CWindVane::GetWindDirectionAsAngle()





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{





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    return g_WindVaneDescriptionTable[DetermineWindDirectionIndex()].DirectionAngle;





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}





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size_t CWindVane::DetermineWindDirectionIndex()





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{





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    float WindVaneSensorVoltage = m_WindVaneAnalogIn.read();





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    // Default to the first entry being closest.





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    size_t ClosestIndex = 0;





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    float  ClosestDelta = fabs(m_WindVaneVoltageTable[0] - WindVaneSensorVoltage);





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    // Walk the rest of the entries to see if there is another which is closer.





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    for (size_t i = 1 ; i < ARRAY_SIZE(m_WindVaneVoltageTable) ; i++)





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    {





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        float Delta = fabs(m_WindVaneVoltageTable[i] - WindVaneSensorVoltage);





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        if (Delta < ClosestDelta)





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        {





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            ClosestDelta = Delta;





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            ClosestIndex = i;





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        }





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    }





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    return ClosestIndex;





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}