Diff: MQ4.h

Revision:

0:401959f72658

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/MQ4.h	Tue Jul 17 04:34:21 2018 +0000
@@ -0,0 +1,55 @@
+#ifndef MQ4_h
+#define MQ4_h
+
+#include "mbed.h"
+
+#define RL_VALUE                    10                                           //define the load resistance on the board, in kilo ohms
+#define RO_DEFAULT                  10                                           //Ro is initialized to 10 kilo ohms
+#define RO_CLEAN_AIR_FACTOR         4.4f                                        //RO_CLEAR_AIR_FACTOR=(Sensor resistance in clean air)/RO, which is derived from the chart in datasheet
+#define CALIBARAION_SAMPLE_TIMES    5                                           //define how many samples you are going to take in the calibration phase
+#define CALIBRATION_SAMPLE_INTERVAL 50                                          //define the time interal(in milisecond) between each samples
+#define READ_SAMPLE_INTERVAL        50                                          //define how many samples you are going to take in normal operation
+#define READ_SAMPLE_TIMES           5                                           //define the time interal(in milisecond) between each samples
+
+//The curves
+// {log(X1) ,log(Y),[log(Y1) - log(Y2)] / [log(X2) - log(X1)]} get values from datasheet             
+static float LPGCurve[]   = {2.3f,0.43f,-0.33f};
+static float H2Curve[]    = {2.3f,0.57f,-0.16f};
+static float CH4Curve[]   = {2.3f,0.27f,-0.38f};
+
+typedef struct {
+  float lpg;
+  float h2;
+  float ch4;
+} MQ4_data_t;
+
+typedef enum  {
+    GAS_LPG = 0,
+    GAS_H2 = 1,
+    GAS_CH4 = 2
+} GasType;
+
+
+class MQ4 {
+public: 
+    MQ4(PinName pin) : _pin(pin){
+      Ro = RO_DEFAULT;
+    };
+    void read(MQ4_data_t *ptr);
+    float readLPG();
+    float readH2();
+    float readCH4();
+    float get_Ro();
+    void begin();
+private:
+    AnalogIn _pin;
+    float MQRead();
+    float MQGetGasPercentage(float rs_ro_ratio, GasType gas_id);
+    int MQGetPercentage(float rs_ro_ratio, float *pcurve);
+    float MQCalibration();
+    float MQResistanceCalculation(int raw_adc);
+    float Ro;
+    
+};
+
+#endif
\ No newline at end of file