Martyn Stopps
The SmoothAnalogIn class provides a smoothed ADC reading; simply setup pin, sample rate, smoothing factor and scaling factor. Useful for processing signals from temperature or pressure sensors etc.
SmoothAnalogIn.cpp@0:d252aa8196fc, 2010-06-18 (annotated)
- Committer:
- stoppsm
- Date:
- Fri Jun 18 13:54:29 2010 +0000
- Revision:
- 0:d252aa8196fc
Who changed what in which revision?
| User | Revision | Line number | New contents of line |
|---|---|---|---|
| stoppsm | 0:d252aa8196fc | 1 | // SmoothAnalogIn.cpp: Martyn Stopps / Taneli Holtta : 18-06-10 |
| stoppsm | 0:d252aa8196fc | 2 | |
| stoppsm | 0:d252aa8196fc | 3 | // Source file: contains implementation that generates the code (the definition) |
| stoppsm | 0:d252aa8196fc | 4 | |
| stoppsm | 0:d252aa8196fc | 5 | #include "SmoothAnalogIn.h" |
| stoppsm | 0:d252aa8196fc | 6 | #include "mbed.h" // tested with revision 23 |
| stoppsm | 0:d252aa8196fc | 7 | |
| stoppsm | 0:d252aa8196fc | 8 | // Constructor - A class that takes arguments PinName, adc sample rate, smoothing factor and scaling factor |
| stoppsm | 0:d252aa8196fc | 9 | |
| stoppsm | 0:d252aa8196fc | 10 | SmoothAnalogIn::SmoothAnalogIn(PinName pin, float sampleRate, int smoothingFactor, int adcScaling) : _adc(pin) { // _adc(pin) means pass pin to the AnalogIn constructor |
| stoppsm | 0:d252aa8196fc | 11 | |
| stoppsm | 0:d252aa8196fc | 12 | _ticker.attach(this, &SmoothAnalogIn::sampleAdc, sampleRate); // attach ticker to member function (delivers adc sampleRate) |
| stoppsm | 0:d252aa8196fc | 13 | |
| stoppsm | 0:d252aa8196fc | 14 | // initialize variables |
| stoppsm | 0:d252aa8196fc | 15 | |
| stoppsm | 0:d252aa8196fc | 16 | _smoothingFactor = smoothingFactor; // mask in the smoothing factor value |
| stoppsm | 0:d252aa8196fc | 17 | _adcScaling = adcScaling; // mask in the adc scaling factor (adc returns 0 to 1 representing 0 to 3.3V) |
| stoppsm | 0:d252aa8196fc | 18 | |
| stoppsm | 0:d252aa8196fc | 19 | } |
| stoppsm | 0:d252aa8196fc | 20 | |
| stoppsm | 0:d252aa8196fc | 21 | |
| stoppsm | 0:d252aa8196fc | 22 | // function - sampleAdc : gets current adc value. |
| stoppsm | 0:d252aa8196fc | 23 | |
| stoppsm | 0:d252aa8196fc | 24 | void SmoothAnalogIn::sampleAdc(void) { |
| stoppsm | 0:d252aa8196fc | 25 | |
| stoppsm | 0:d252aa8196fc | 26 | double adc_value = _adc.read()*_adcScaling; // read _adc pin analog value * _adcScaling |
| stoppsm | 0:d252aa8196fc | 27 | SmoothAnalogIn::smoothValue(adc_value); // call smoothing function passing in current scaled adc_value |
| stoppsm | 0:d252aa8196fc | 28 | } |
| stoppsm | 0:d252aa8196fc | 29 | |
| stoppsm | 0:d252aa8196fc | 30 | |
| stoppsm | 0:d252aa8196fc | 31 | // function - smoothValue : Smoothing algorithm |
| stoppsm | 0:d252aa8196fc | 32 | |
| stoppsm | 0:d252aa8196fc | 33 | void SmoothAnalogIn::smoothValue(double newValue) { |
| stoppsm | 0:d252aa8196fc | 34 | |
| stoppsm | 0:d252aa8196fc | 35 | if (newValue > smoothed) smoothed = smoothed + ((newValue - smoothed)/_smoothingFactor); // rawValue > smoothed value |
| stoppsm | 0:d252aa8196fc | 36 | else if (newValue < smoothed) smoothed = smoothed - ((smoothed - newValue)/_smoothingFactor); // rawValue < smoothed value |
| stoppsm | 0:d252aa8196fc | 37 | } |
| stoppsm | 0:d252aa8196fc | 38 | |
| stoppsm | 0:d252aa8196fc | 39 | |
| stoppsm | 0:d252aa8196fc | 40 | // function - read : returns smoothed adc value |
| stoppsm | 0:d252aa8196fc | 41 | |
| stoppsm | 0:d252aa8196fc | 42 | double SmoothAnalogIn::read(void) { |
| stoppsm | 0:d252aa8196fc | 43 | |
| stoppsm | 0:d252aa8196fc | 44 | return(smoothed); |
| stoppsm | 0:d252aa8196fc | 45 | } |