Diff: omegaPX209/omegaPX209.cpp

Revision:

14:85b64a4d08e8

Parent:

10:085ab7328054

Child:

17:7c16b5671d0e

--- a/omegaPX209/omegaPX209.cpp	Mon Oct 30 21:09:19 2017 +0000
+++ b/omegaPX209/omegaPX209.cpp	Tue Oct 31 17:06:52 2017 +0000
@@ -1,35 +1,64 @@
 /*
-Matthew Kelly
-October 24th, 2013
-The purpose of this class is to define a a data structure with all of the necessary information and member functions...
-to fully describe a single ultrasonic transducer for use in a relative positioning system.
+This class wraps an Omega pressure transducer.
+Author: Matthew, October 24th, 2013
+Modified: Dan, 2017-10-30
 */
 
 #include "mbed.h"
 #include "omegaPX209.hpp"
 
 omegaPX209::omegaPX209(PinName pin): 
-    depthP(pin)
+    _adc(pin)
 {
+    _psi = 14.7;                    // pressure [psi]
+    _zeroPsi = 14.7;                // atmospheric pressure at sea level [psi]
+    _adcVoltage = 3.3;              // mbed ADC system voltage [V]
+    _fullscale = 50;                // value of sensor at full scale (*confirm with Stearns*) [psi]
+    _cal = _fullscale/5.0;          // psi per volt calibration [psi/V]
 }
 
-void omegaPX209::initialize() {
-    P = 0;              // Pressure [psi]
-    cal = 12;           // Volts per psi
-    multiplier = 3.3;   // Maximum voltage in
+// nothing to initialize, but you can call this function if it makes you feel better.
+void omegaPX209::init() {
+}
+
+// lets user set a different ambient pressure [psi]
+void omegaPX209::setZero(float zeroPsi) {
+    _zeroPsi = zeroPsi;    
+}
+
+// returns the internal ambient pressure [psi]
+float omegaPX209::getZero() {
+    return _zeroPsi;
 }
 
+// reads from ADC system and does math for converting to psi
 float omegaPX209::getPsi() {
-    P = depthP*multiplier*cal;
-    return P;
+    // filter by over-sampling
+    float add = 0;
+    for (int i = 0; i < OVERSAMPLE; i++) {
+        // analog input _adc is float 0.0 to 1.0
+        // multiplying by _adcVoltage converts percentage to a voltage
+        // multiplying by _cal converts voltage to a pressure
+        add += _adc.read() * _adcVoltage * _cal;
+    }
+    
+    // use over-sampled
+    _psi = (add/OVERSAMPLE);
+
+    return _psi;
 }
 
-// math sourced from http://www.kylesconverter.com/pressure/feet-of-water-to-pounds-per-square-inch
-float omegaPX209::getDepth() {
-    P = getPsi(); // read the sensor
-    float pascals = (P * 6894.76) - (14.7 * 6894.76); // convert psi to Pascals
-    float depth_m = pascals / (density_of_water_g_cc * 1000 * 9.80665); // convert Pa to fluid depth in meters
-    float depth_ft = 3.28084 * depth_m; // convert meters to feet
-    
+// reads the ADC system and returns depth in feet
+float omegaPX209::getDepthFt() {
+    float psi = getPsi() - _zeroPsi; // read the sensor and remove atmospheric bias
+    float Pa = psi2Pa * psi; // convert psi to Pascals
+    float depth_m = Pa / (water_density_kg_m3 * grav_m_s2); // convert Pa to fluid depth in meters
+    float depth_ft = m2ft * depth_m; // convert meters to feet
+
     return depth_ft;
+}
+
+// call this if you want to tare to zero
+float omegaPX209::tare() {
+    setZero(getPsi());
 }
\ No newline at end of file