Y SI / lib_SHT25

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Dependents:   lib_SHT25_example

lib_SHT25.cpp@1:ebd95757fba4, 2018-06-18 (annotated)

Committer:
YSI
Date:
Mon Jun 18 08:28:52 2018 +0000
Revision:
1:ebd95757fba4
Parent:
0:71da3fbfe141
Child:
2:34e14b4cd981
Doc updated

Who changed what in which revision?

UserRevisionLine numberNew contents of line
YSI 0:71da3fbfe141 1 /** SHT25 class
YSI 0:71da3fbfe141 2 *
YSI 0:71da3fbfe141 3 * @purpose library for SHT25 humidity and temperature sensor
YSI 0:71da3fbfe141 4 *
YSI 0:71da3fbfe141 5 * Use to get temperature and humidity
YSI 0:71da3fbfe141 6 *
YSI 0:71da3fbfe141 7 * https://www.sensirion.com/products/humidity-sensor/
YSI 0:71da3fbfe141 8 *
YSI 0:71da3fbfe141 9 * Example:
YSI 0:71da3fbfe141 10 * @code
YSI 0:71da3fbfe141 11 * #include "mbed.h"
YSI 0:71da3fbfe141 12 * #include "lib_SHT25.h"
YSI 0:71da3fbfe141 13 *
YSI 0:71da3fbfe141 14 * Serial pc(USBTX, USBRX);
YSI 0:71da3fbfe141 15 * SHT25 sensor(p28, p27);
YSI 0:71da3fbfe141 16 *
YSI 0:71da3fbfe141 17 * int main()
YSI 0:71da3fbfe141 18 * {
YSI 0:71da3fbfe141 19 * float temperature, humidity;
YSI 0:71da3fbfe141 20 * while(1)
YSI 0:71da3fbfe141 21 * {
YSI 0:71da3fbfe141 22 * sensor.getData(&temperature, &humidity);
YSI 0:71da3fbfe141 23 * pc.printf("\rtemperature = %6.2f%cC -|- humidity = %6.2f%%RH", temperature, 248, humidity);
YSI 0:71da3fbfe141 24 * wait(0.5);
YSI 0:71da3fbfe141 25 * }
YSI 0:71da3fbfe141 26 * }
YSI 0:71da3fbfe141 27 * @endcode
YSI 1:ebd95757fba4 28 * @file lib_SHT25.cpp
YSI 0:71da3fbfe141 29 * @date Jun 2018
YSI 0:71da3fbfe141 30 * @author Yannic Simon
YSI 0:71da3fbfe141 31 */
YSI 0:71da3fbfe141 32 #include "lib_SHT25.h"
YSI 0:71da3fbfe141 33
YSI 0:71da3fbfe141 34 SHT25::SHT25(PinName sda, PinName scl) : _i2c(sda, scl)
YSI 0:71da3fbfe141 35 {
YSI 0:71da3fbfe141 36 softReset();
YSI 0:71da3fbfe141 37 wait_ms(100);
YSI 0:71da3fbfe141 38 setPrecision(SHT_PREC_1214);
YSI 0:71da3fbfe141 39 _selfHeat = true;
YSI 0:71da3fbfe141 40 }
YSI 0:71da3fbfe141 41
YSI 0:71da3fbfe141 42 float SHT25::getTemperature(void)
YSI 0:71da3fbfe141 43 {
YSI 0:71da3fbfe141 44 if(_selfHeat)
YSI 0:71da3fbfe141 45 {
YSI 0:71da3fbfe141 46 _selfHeat = false;
YSI 0:71da3fbfe141 47 _t.attach(callback(this, &SHT25::keepSelf), SHT_SELF_HEATING);
YSI 0:71da3fbfe141 48 return readTemperature();
YSI 0:71da3fbfe141 49 }
YSI 0:71da3fbfe141 50 return _temperature;
YSI 0:71da3fbfe141 51 }
YSI 0:71da3fbfe141 52
YSI 0:71da3fbfe141 53 float SHT25::readTemperature(void)
YSI 0:71da3fbfe141 54 {
YSI 0:71da3fbfe141 55 char command[1] = {SHT_TRIG_TEMP}, rx[3] = {0xFF, 0xFF, 0xFF};
YSI 0:71da3fbfe141 56
YSI 0:71da3fbfe141 57 _i2c.write(SHT_I2C_ADDR, command, 1, false);
YSI 0:71da3fbfe141 58 wait_ms(85);
YSI 0:71da3fbfe141 59 _i2c.read(SHT_I2C_ADDR, rx, 3, false);
YSI 0:71da3fbfe141 60
YSI 0:71da3fbfe141 61 return _temperature = -46.85 + 175.72 * ((((rx[0] << 8) | rx[1]) & 0xFFFC) / 65536.0);
YSI 0:71da3fbfe141 62 }
YSI 0:71da3fbfe141 63
YSI 0:71da3fbfe141 64 float SHT25::getHumidity(void)
YSI 0:71da3fbfe141 65 {
YSI 0:71da3fbfe141 66 if(_selfHeat)
YSI 0:71da3fbfe141 67 {
YSI 0:71da3fbfe141 68 _selfHeat = false;
YSI 0:71da3fbfe141 69 _t.attach(callback(this, &SHT25::keepSelf), SHT_SELF_HEATING);
YSI 0:71da3fbfe141 70 return readHumidity();
YSI 0:71da3fbfe141 71 }
YSI 0:71da3fbfe141 72 return _humidity;
YSI 0:71da3fbfe141 73 }
YSI 0:71da3fbfe141 74
YSI 0:71da3fbfe141 75 float SHT25::readHumidity(void)
YSI 0:71da3fbfe141 76 {
YSI 0:71da3fbfe141 77 char command[1] = {SHT_TRIG_RH}, rx[3] = {0xFF, 0xFF, 0xFF};
YSI 0:71da3fbfe141 78
YSI 0:71da3fbfe141 79 _i2c.write(SHT_I2C_ADDR, command, 1, false);
YSI 0:71da3fbfe141 80 wait_ms(29);
YSI 0:71da3fbfe141 81 _i2c.read(SHT_I2C_ADDR, rx, 3, false);
YSI 0:71da3fbfe141 82
YSI 0:71da3fbfe141 83 return _humidity = -6.0 + 125.0 * ((((rx[0] << 8) | rx[1]) & 0xFFFC) / 65536.0);
YSI 0:71da3fbfe141 84 }
YSI 0:71da3fbfe141 85
YSI 0:71da3fbfe141 86 void SHT25::getData(float *tempC, float *relHumidity)
YSI 0:71da3fbfe141 87 {
YSI 0:71da3fbfe141 88 if(_selfHeat)
YSI 0:71da3fbfe141 89 {
YSI 0:71da3fbfe141 90 _selfHeat = false;
YSI 0:71da3fbfe141 91 _t.attach(callback(this, &SHT25::keepSelf), SHT_SELF_HEATING);
YSI 0:71da3fbfe141 92 readData(tempC, relHumidity);
YSI 0:71da3fbfe141 93 }
YSI 0:71da3fbfe141 94 }
YSI 0:71da3fbfe141 95
YSI 0:71da3fbfe141 96 void SHT25::readData(float *tempC, float *relHumidity)
YSI 0:71da3fbfe141 97 {
YSI 0:71da3fbfe141 98 *tempC = readTemperature();
YSI 0:71da3fbfe141 99 *relHumidity = readHumidity();
YSI 0:71da3fbfe141 100 }
YSI 0:71da3fbfe141 101
YSI 0:71da3fbfe141 102 int SHT25::setPrecision(char precision)
YSI 0:71da3fbfe141 103 {
YSI 0:71da3fbfe141 104 char command[2] = {SHT_WRITE_REG, precision};
YSI 0:71da3fbfe141 105
YSI 0:71da3fbfe141 106 return _i2c.write(SHT_I2C_ADDR, command, 2, false);
YSI 0:71da3fbfe141 107 }
YSI 0:71da3fbfe141 108
YSI 0:71da3fbfe141 109 bool SHT25::softReset()
YSI 0:71da3fbfe141 110 {
YSI 0:71da3fbfe141 111 char command[1] = {SHT_SOFT_RESET};
YSI 0:71da3fbfe141 112
YSI 0:71da3fbfe141 113 if (_i2c.write(SHT_I2C_ADDR, command, 1, false) != 0)
YSI 0:71da3fbfe141 114 {
YSI 0:71da3fbfe141 115 wait_ms(15);
YSI 0:71da3fbfe141 116 return false;
YSI 0:71da3fbfe141 117 }
YSI 0:71da3fbfe141 118
YSI 0:71da3fbfe141 119 return true;
YSI 0:71da3fbfe141 120 }
YSI 0:71da3fbfe141 121
YSI 0:71da3fbfe141 122 void SHT25::keepSelf(void)
YSI 0:71da3fbfe141 123 {
YSI 0:71da3fbfe141 124 _selfHeat = true;
YSI 0:71da3fbfe141 125 }