Diff: HTU21D/HTU21D.cpp

Revision:

0:1159c687a20f

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/HTU21D/HTU21D.cpp	Thu Mar 21 09:44:17 2019 +0000
@@ -0,0 +1,97 @@
+#include "HTU21D.h"
+ 
+
+
+
+
+#if defined(__TT_M4G9__) | defined(__TT_M3HQ__)
+#define DEFAULT_SDA_PIN  I2C_SDA
+#define DEFAULT_SCL_PIN  I2C_SCL
+#endif
+
+
+
+HTU21D::HTU21D()
+{
+    i2c_ = new I2C(DEFAULT_SDA_PIN, DEFAULT_SCL_PIN);
+    i2c_->frequency(400000);
+}
+
+
+HTU21D::HTU21D(PinName sda, PinName scl) {
+ 
+    i2c_ = new I2C(sda, scl);
+    //400KHz, as specified by the datasheet.
+    i2c_->frequency(400000);
+ 
+ 
+ 
+}
+ 
+int HTU21D::sample_ctemp(void) {
+ 
+    char tx[1];
+    char rx[2];
+    int status ;
+    tx[0] = TRIGGER_TEMP_MEASURE; // Triggers a temperature measure by feeding correct opcode.
+    i2c_->write((HTU21D_I2C_ADDRESS << 1) & 0xFE, tx, 1);
+    wait_ms(50); // Per datasheet, wait long enough for device to sample temperature
+    
+    // Reads triggered measure
+    i2c_->read((HTU21D_I2C_ADDRESS << 1) | 0x01, rx, 2);
+    wait_ms(1);
+
+    // Algorithm from datasheet to compute temperature.
+    unsigned int rawTemperature = ((unsigned int) rx[0] << 8) | (unsigned int) rx[1];
+    rawTemperature &= 0xFFFC;
+ 
+    float tempTemperature = rawTemperature / (float)65536; //2^16 = 65536
+    float realTemperature = -46.85 + (175.72 * tempTemperature); //From page 14
+ 
+    return (int)realTemperature;
+ 
+}
+ 
+int HTU21D::sample_ftemp(void){
+    int temptemp = sample_ctemp();
+    int ftemp = temptemp * 1.8 + 32;
+    
+    return ftemp;
+}
+ 
+int HTU21D::sample_ktemp(void){
+    int temptemp = sample_ctemp();
+    int ktemp = temptemp + 274;
+    
+    return ktemp;
+    
+    
+}
+ 
+int HTU21D::sample_humid(void) {
+ 
+    char tx[1];
+    char rx[2];
+ 
+ 
+    tx[0] = TRIGGER_HUMD_MEASURE; // Triggers a humidity measure by feeding correct opcode.
+    i2c_->write((HTU21D_I2C_ADDRESS << 1) & 0xFE, tx, 1);
+    wait_ms(16); // Per datasheet, wait long enough for device to sample humidity
+    
+    // Reads triggered measure
+    i2c_->read((HTU21D_I2C_ADDRESS << 1) | 0x01, rx, 2);
+    wait_ms(1);
+    
+    //Algorithm from datasheet.
+    unsigned int rawHumidity = ((unsigned int) rx[0] << 8) | (unsigned int) rx[1];
+ 
+    rawHumidity &= 0xFFFC; //Zero out the status bits but keep them in place
+    
+    //Given the raw humidity data, calculate the actual relative humidity
+    float tempRH = rawHumidity / (float)65536; //2^16 = 65536
+    float rh = -6 + (125 * tempRH); //From page 14
+ 
+ 
+    return (int)rh;
+ 
+}