Team Eta / Mbed OS Smart_Baby_Monitor

Smart

Dependencies:   Hexi_KW40Z

HTU21D.cpp@0:69293b19ee19, 2018-02-28 (annotated)

Committer:
Team_Eta_MBED
Date:
Wed Feb 28 16:34:40 2018 +0000
Revision:
0:69293b19ee19
Smart Baby Monitor Foundations

Who changed what in which revision?

UserRevisionLine numberNew contents of line
Team_Eta_MBED 0:69293b19ee19 1 // EE 4391 Senior Design
Team_Eta_MBED 0:69293b19ee19 2 // Professor Hinkle and Dr. Compeau
Team_Eta_MBED 0:69293b19ee19 3 // @author Team Eta
Team_Eta_MBED 0:69293b19ee19 4 // Texas State University
Team_Eta_MBED 0:69293b19ee19 5
Team_Eta_MBED 0:69293b19ee19 6 // @section DESCRIPTION
Team_Eta_MBED 0:69293b19ee19 7 // HTU21D Humidity and Temperature sensor.
Team_Eta_MBED 0:69293b19ee19 8 // Datasheet, specs, and information:
Team_Eta_MBED 0:69293b19ee19 9 // https://cdn.sparkfun.com/assets/6/a/8/e/f/525778d4757b7f50398b4567.pdf
Team_Eta_MBED 0:69293b19ee19 10
Team_Eta_MBED 0:69293b19ee19 11
Team_Eta_MBED 0:69293b19ee19 12 #include "HTU21D.h"
Team_Eta_MBED 0:69293b19ee19 13
Team_Eta_MBED 0:69293b19ee19 14 HTU21D::HTU21D(PinName sda, PinName scl) {
Team_Eta_MBED 0:69293b19ee19 15
Team_Eta_MBED 0:69293b19ee19 16 i2c_ = new I2C(sda, scl);
Team_Eta_MBED 0:69293b19ee19 17 //400KHz, as specified by the datasheet page 3.
Team_Eta_MBED 0:69293b19ee19 18 i2c_->frequency(400000);
Team_Eta_MBED 0:69293b19ee19 19 }
Team_Eta_MBED 0:69293b19ee19 20
Team_Eta_MBED 0:69293b19ee19 21 int HTU21D::sample_ctemp(void) {
Team_Eta_MBED 0:69293b19ee19 22
Team_Eta_MBED 0:69293b19ee19 23 char tx[1];
Team_Eta_MBED 0:69293b19ee19 24 char rx[2];
Team_Eta_MBED 0:69293b19ee19 25
Team_Eta_MBED 0:69293b19ee19 26 tx[0] = TRIGGER_TEMP_MEASURE; // Triggers a temperature measure by feeding correct opcode.
Team_Eta_MBED 0:69293b19ee19 27 i2c_->write((HTU21D_I2C_ADDRESS << 1) & 0xFE, tx, 1);
Team_Eta_MBED 0:69293b19ee19 28 wait_ms(50); // Per datasheet, wait long enough for device to sample temperature
Team_Eta_MBED 0:69293b19ee19 29
Team_Eta_MBED 0:69293b19ee19 30 // Reads triggered measure
Team_Eta_MBED 0:69293b19ee19 31 i2c_->read((HTU21D_I2C_ADDRESS << 1) | 0x01, rx, 2);
Team_Eta_MBED 0:69293b19ee19 32 wait_ms(1);
Team_Eta_MBED 0:69293b19ee19 33
Team_Eta_MBED 0:69293b19ee19 34 // Algorithm from datasheet to compute temperature.
Team_Eta_MBED 0:69293b19ee19 35 unsigned int rawTemperature = ((unsigned int) rx[0] << 8) | (unsigned int) rx[1];
Team_Eta_MBED 0:69293b19ee19 36 rawTemperature &= 0xFFFC;
Team_Eta_MBED 0:69293b19ee19 37
Team_Eta_MBED 0:69293b19ee19 38 float tempTemperature = rawTemperature / (float)65536; //2^16 = 65536
Team_Eta_MBED 0:69293b19ee19 39 float realTemperature = -46.85 + (175.72 * tempTemperature); //From page 14
Team_Eta_MBED 0:69293b19ee19 40
Team_Eta_MBED 0:69293b19ee19 41 return (int)realTemperature;
Team_Eta_MBED 0:69293b19ee19 42 }
Team_Eta_MBED 0:69293b19ee19 43
Team_Eta_MBED 0:69293b19ee19 44 int HTU21D::sample_ftemp(void){
Team_Eta_MBED 0:69293b19ee19 45 int temptemp = sample_ctemp();
Team_Eta_MBED 0:69293b19ee19 46 int ftemp = temptemp * 1.8 + 32; //Change this value to fit our Hexiwear or adjut temperature calibration -- "16" used to be "32"
Team_Eta_MBED 0:69293b19ee19 47
Team_Eta_MBED 0:69293b19ee19 48 return ftemp;
Team_Eta_MBED 0:69293b19ee19 49 }
Team_Eta_MBED 0:69293b19ee19 50
Team_Eta_MBED 0:69293b19ee19 51 int HTU21D::sample_ktemp(void){
Team_Eta_MBED 0:69293b19ee19 52 int temptemp = sample_ctemp();
Team_Eta_MBED 0:69293b19ee19 53 int ktemp = temptemp + 274;
Team_Eta_MBED 0:69293b19ee19 54
Team_Eta_MBED 0:69293b19ee19 55 return ktemp;
Team_Eta_MBED 0:69293b19ee19 56 }
Team_Eta_MBED 0:69293b19ee19 57
Team_Eta_MBED 0:69293b19ee19 58 int HTU21D::sample_humid(void) {
Team_Eta_MBED 0:69293b19ee19 59
Team_Eta_MBED 0:69293b19ee19 60 char tx[1];
Team_Eta_MBED 0:69293b19ee19 61 char rx[2];
Team_Eta_MBED 0:69293b19ee19 62
Team_Eta_MBED 0:69293b19ee19 63
Team_Eta_MBED 0:69293b19ee19 64 tx[0] = TRIGGER_HUMD_MEASURE; // Triggers a humidity measure by feeding correct opcode.
Team_Eta_MBED 0:69293b19ee19 65 i2c_->write((HTU21D_I2C_ADDRESS << 1) & 0xFE, tx, 1);
Team_Eta_MBED 0:69293b19ee19 66 wait_ms(16); // Per datasheet, wait long enough for device to sample humidity
Team_Eta_MBED 0:69293b19ee19 67
Team_Eta_MBED 0:69293b19ee19 68 // Reads triggered measure
Team_Eta_MBED 0:69293b19ee19 69 i2c_->read((HTU21D_I2C_ADDRESS << 1) | 0x01, rx, 2);
Team_Eta_MBED 0:69293b19ee19 70 wait_ms(1);
Team_Eta_MBED 0:69293b19ee19 71
Team_Eta_MBED 0:69293b19ee19 72 //Algorithm from datasheet.
Team_Eta_MBED 0:69293b19ee19 73 unsigned int rawHumidity = ((unsigned int) rx[0] << 8) | (unsigned int) rx[1];
Team_Eta_MBED 0:69293b19ee19 74
Team_Eta_MBED 0:69293b19ee19 75 rawHumidity &= 0xFFFC; //Zero out the status bits but keep them in place
Team_Eta_MBED 0:69293b19ee19 76
Team_Eta_MBED 0:69293b19ee19 77 //Given the raw humidity data, calculate the actual relative humidity
Team_Eta_MBED 0:69293b19ee19 78 float tempRH = rawHumidity / (float)65536; //2^16 = 65536
Team_Eta_MBED 0:69293b19ee19 79 float rh = 20 + (125 * tempRH); //From page 14 --- "20" used to be "-6"
Team_Eta_MBED 0:69293b19ee19 80
Team_Eta_MBED 0:69293b19ee19 81 return (int)rh;
Team_Eta_MBED 0:69293b19ee19 82 }
Team_Eta_MBED 0:69293b19ee19 83