Diff: pressure_sensors.cpp

Revision:

9:95fdcdc0977e

Parent:

8:208d965a3bd2

Child:

11:5cb7ae8bd831

--- a/pressure_sensors.cpp	Thu Apr 23 17:05:36 2020 +0000
+++ b/pressure_sensors.cpp	Sun Apr 26 08:50:12 2020 +0000
@@ -14,6 +14,7 @@
 int16_t pressure_01_bin, pressure_02_bin;
 float pressure_01_psi, pressure_02_psi;
 float flow_lpm, volume_ml;
+float lpf_01_prev_out, lpf_02_prev_out;
 
 //float diff_pressure_psi;
 
@@ -22,33 +23,73 @@
 /* Function definition */
 
 void Pressure_Sensors_Initialize(void){
+    
+    int16_t sensor_01_aux, sensor_02_aux;
+    
     pressure_sensor_01.frequency(PRESSURE_SENSOR_I2C_CLK_HZ ); 
     pressure_sensor_02.frequency(PRESSURE_SENSOR_I2C_CLK_HZ );
+    
+    /* Perform an initial measurement */
+
+    pressure_sensor_01.read(PRESSURE_SENSOR_01_SRA, sensor_read_data_buffer, 2);
+    sensor_01_aux = ((sensor_read_data_buffer[0] << 8) | sensor_read_data_buffer[1]) & 0x3FFF;
+    
+    if(sensor_01_aux < PRESSURE_SENSOR_OUTPUT_MIN){
+        sensor_01_aux = PRESSURE_SENSOR_OUTPUT_MIN;
+    }    
+    
+    pressure_sensor_02.read(PRESSURE_SENSOR_02_SRA, sensor_read_data_buffer, 2);
+    sensor_02_aux = ((sensor_read_data_buffer[0] << 8) | sensor_read_data_buffer[1]) & 0x3FFF;
+
+    if(sensor_02_aux < PRESSURE_SENSOR_OUTPUT_MIN){
+        sensor_02_aux = PRESSURE_SENSOR_OUTPUT_MIN;
+    }    
+        
+    lpf_01_prev_out = (float)sensor_01_aux;
+    lpf_02_prev_out = (float)sensor_02_aux;
+
 }
 
 
 void Pressure_Sensors_Read(void){
     
+    int16_t raw_pressure_01_bin, raw_pressure_02_bin;
+    
     /* Read binary values */
     pressure_sensor_01.read(PRESSURE_SENSOR_01_SRA, sensor_read_data_buffer, 2);
-    pressure_01_bin = ((sensor_read_data_buffer[0] << 8) | sensor_read_data_buffer[1]) & 0x3FFF;
+    raw_pressure_01_bin = ((sensor_read_data_buffer[0] << 8) | sensor_read_data_buffer[1]) & 0x3FFF;
+    
+    if(raw_pressure_01_bin < PRESSURE_SENSOR_OUTPUT_MIN){
+        raw_pressure_01_bin = PRESSURE_SENSOR_OUTPUT_MIN;
+    }
+
     pressure_sensor_02.read(PRESSURE_SENSOR_02_SRA, sensor_read_data_buffer, 2);
-    pressure_02_bin = ((sensor_read_data_buffer[0] << 8) | sensor_read_data_buffer[1]) & 0x3FFF;
+    raw_pressure_02_bin = ((sensor_read_data_buffer[0] << 8) | sensor_read_data_buffer[1]) & 0x3FFF;
+    
+    if(raw_pressure_02_bin < PRESSURE_SENSOR_OUTPUT_MIN){
+        raw_pressure_02_bin = PRESSURE_SENSOR_OUTPUT_MIN;
+    }    
+    
+    /* Filter binary values */
+    pressure_01_bin = Low_Pass_Filter_01(raw_pressure_01_bin);
+    pressure_02_bin = Low_Pass_Filter_02(raw_pressure_02_bin);
     
     /* Calculate pressure values in PSI */
-    pressure_01_psi = (5.0 * pressure_01_bin) / 16383; 
-    pressure_02_psi = (5.0 * pressure_02_bin) / 16383;
+    pressure_01_psi = (pressure_01_bin - PRESSURE_SENSOR_OUTPUT_MIN) * (PRESSURE_SENSOR_PRESSURE_MAX - PRESSURE_SENSOR_PRESSURE_MIN);
+    pressure_01_psi = (pressure_01_psi / (PRESSURE_SENSOR_OUTPUT_MAX - PRESSURE_SENSOR_OUTPUT_MIN)) + PRESSURE_SENSOR_PRESSURE_MIN;
+    //pressure_01_psi += PRESSURE_SENSOR_OFFSET_PSI;
+    pressure_02_psi = (pressure_02_bin - PRESSURE_SENSOR_OUTPUT_MIN) * (PRESSURE_SENSOR_PRESSURE_MAX - PRESSURE_SENSOR_PRESSURE_MIN);
+    pressure_02_psi = (pressure_02_psi / (PRESSURE_SENSOR_OUTPUT_MAX - PRESSURE_SENSOR_OUTPUT_MIN)) + PRESSURE_SENSOR_PRESSURE_MIN;
+    //pressure_02_psi += PRESSURE_SENSOR_OFFSET_PSI;
+} 
 
-    
-} 
+
 
 void Calculate_Flow_From_Pressure(void){
     
-    int16_t diff_pressure_bin;
     float diff_pressure_psi;
     
-    diff_pressure_bin =  pressure_02_bin - pressure_01_bin;
-    diff_pressure_psi = (5.0 * diff_pressure_bin) / 16383;
+    diff_pressure_psi = pressure_02_psi - pressure_01_psi;
     
     if(diff_pressure_psi < 0){
         flow_lpm = -SPIROMETER_SENSOR_CONSTANT * sqrt(-diff_pressure_psi);    
@@ -70,11 +111,30 @@
     
 }
 
-void Pressure_01_LPF(void){
+int16_t Low_Pass_Filter_01(int16_t raw_value){
+    
+    float lpf_out, sample_period_sec, div;
+    
+    sample_period_sec = 0.001 * ((float)PRESSURE_SENSOR_READ_PERIOD_MS);
+    div = sample_period_sec + LPF_RC_CONSTANT_SEC;
+    
+    lpf_out = (((float)raw_value) * (sample_period_sec / div)) +  (lpf_01_prev_out * (LPF_RC_CONSTANT_SEC / div));
+    lpf_01_prev_out = lpf_out;
+    
+    return ((int16_t)lpf_out);
 
 }
 
 
-void Pressure_02_LPF(void){
+int16_t Low_Pass_Filter_02(int16_t raw_value){
 
+    float lpf_out, sample_period_sec, div;
+    
+    sample_period_sec = 0.001 * ((float)PRESSURE_SENSOR_READ_PERIOD_MS);
+    div = sample_period_sec + LPF_RC_CONSTANT_SEC;
+    
+    lpf_out = (((float)raw_value) * (sample_period_sec / div)) +  (lpf_02_prev_out * (LPF_RC_CONSTANT_SEC / div));
+    lpf_02_prev_out = lpf_out;
+    
+    return ((int16_t)lpf_out);
 }