Y SI / lib_SHT25

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Dependents:   lib_SHT25_example

lib_SHT25.cpp@7:b55223269e6b, 2021-09-16 (annotated)

Committer:
YSI
Date:
Thu Sep 16 11:17:17 2021 +0000
Revision:
7:b55223269e6b
Parent:
5:8e34f365eb45
Child:
8:bb3dbc86a180
Fix I2C read address, change I2C frequency to 400KHz, remove all sleep or wait functions.

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 "lib_SHT25.h"
YSI 0:71da3fbfe141 12 *
YSI 0:71da3fbfe141 13 * Serial pc(USBTX, USBRX);
YSI 3:81324c19d870 14 * SHT25 sensor(I2C_SDA, I2C_SCL);
YSI 0:71da3fbfe141 15 *
YSI 0:71da3fbfe141 16 * int main()
YSI 0:71da3fbfe141 17 * {
YSI 0:71da3fbfe141 18 * float temperature, humidity;
YSI 0:71da3fbfe141 19 * while(1)
YSI 0:71da3fbfe141 20 * {
YSI 3:81324c19d870 21 * temperature = sensor.getTemperature();
YSI 3:81324c19d870 22 * humidity = sensor.getTemperature();
YSI 3:81324c19d870 23 * pc.printf("\r\ntemperature = %6.2f%cC -|- humidity = %6.2f%%RH", temperature, 248, humidity);
YSI 3:81324c19d870 24 * sensor.waitSafeHeat();
YSI 0:71da3fbfe141 25 * sensor.getData(&temperature, &humidity);
YSI 3:81324c19d870 26 * pc.printf("\ntemperature = %6.2f%cC -|- humidity = %6.2f%%RH", temperature, 248, humidity);
YSI 3:81324c19d870 27 * sensor.waitSafeHeat();
YSI 0:71da3fbfe141 28 * }
YSI 0:71da3fbfe141 29 * }
YSI 0:71da3fbfe141 30 * @endcode
YSI 1:ebd95757fba4 31 * @file lib_SHT25.cpp
YSI 0:71da3fbfe141 32 * @date Jun 2018
YSI 0:71da3fbfe141 33 * @author Yannic Simon
YSI 0:71da3fbfe141 34 */
YSI 0:71da3fbfe141 35 #include "lib_SHT25.h"
YSI 0:71da3fbfe141 36
YSI 7:b55223269e6b 37 SHT25::SHT25(PinName sda, PinName scl, enum_sht_prec prec, int frequency) : _i2c(sda, scl)
YSI 0:71da3fbfe141 38 {
YSI 7:b55223269e6b 39 _i2c.frequency(frequency);
YSI 7:b55223269e6b 40 setPrecision(prec);
YSI 7:b55223269e6b 41 _temperature = _humidity = NAN;
YSI 7:b55223269e6b 42 _selfHeatTemperature = _selfHeatHumidity = false;
YSI 7:b55223269e6b 43 _t.attach(callback(this, &SHT25::keepSafeTemperature), SHT_SELF_HEATING);
YSI 7:b55223269e6b 44 _h.attach(callback(this, &SHT25::keepSafeHumidity), SHT_SELF_HEATING);
YSI 0:71da3fbfe141 45 }
YSI 0:71da3fbfe141 46
YSI 0:71da3fbfe141 47 void SHT25::getData(float *tempC, float *relHumidity)
YSI 0:71da3fbfe141 48 {
YSI 7:b55223269e6b 49 *tempC = _temperature;
YSI 7:b55223269e6b 50 *relHumidity = _humidity;
YSI 3:81324c19d870 51 if(_selfHeatTemperature && _selfHeatHumidity)
YSI 0:71da3fbfe141 52 readData(tempC, relHumidity);
YSI 0:71da3fbfe141 53 }
YSI 0:71da3fbfe141 54
YSI 0:71da3fbfe141 55 void SHT25::readData(float *tempC, float *relHumidity)
YSI 0:71da3fbfe141 56 {
YSI 2:34e14b4cd981 57 *tempC = _temperature = readTemperature();
YSI 2:34e14b4cd981 58 *relHumidity = _humidity = readHumidity();
YSI 0:71da3fbfe141 59 }
YSI 0:71da3fbfe141 60
YSI 7:b55223269e6b 61 float SHT25::getTemperature(void)
YSI 7:b55223269e6b 62 {
YSI 7:b55223269e6b 63 if(_selfHeatTemperature)
YSI 7:b55223269e6b 64 _temperature = readTemperature();
YSI 7:b55223269e6b 65 return _temperature;
YSI 7:b55223269e6b 66 }
YSI 7:b55223269e6b 67
YSI 7:b55223269e6b 68 float SHT25::readTemperature(void)
YSI 7:b55223269e6b 69 {
YSI 7:b55223269e6b 70 char cmd[1] = {SHT_TRIG_TEMP_NHOLD}, rx[3] = {0xFF, 0xFF, 0xFF};
YSI 7:b55223269e6b 71 if(!_i2c.write(SHT_I2C_ADDR_WRITE, cmd, 1, false))
YSI 7:b55223269e6b 72 {
YSI 7:b55223269e6b 73 for(int i = 0; _i2c.read(SHT_I2C_ADDR_READ, rx, 3, false) && (i < 1889); i++); //1889*45ms(time to read at 400KHz) = 85ms(time max to measure T on 14bit)
YSI 7:b55223269e6b 74 _selfHeatTemperature = false;
YSI 7:b55223269e6b 75 _t.attach(callback(this, &SHT25::keepSafeTemperature), SHT_SELF_HEATING);
YSI 7:b55223269e6b 76 return -46.85f + 175.72f * ((((rx[0] << 8) | rx[1]) & 0xFFFC) / 65536.0f);
YSI 7:b55223269e6b 77 }
YSI 7:b55223269e6b 78 return NAN;
YSI 7:b55223269e6b 79 }
YSI 7:b55223269e6b 80
YSI 7:b55223269e6b 81 float SHT25::getHumidity(void)
YSI 7:b55223269e6b 82 {
YSI 7:b55223269e6b 83 if(_selfHeatHumidity)
YSI 7:b55223269e6b 84 _humidity = readHumidity();
YSI 7:b55223269e6b 85 return _humidity;
YSI 7:b55223269e6b 86 }
YSI 7:b55223269e6b 87
YSI 7:b55223269e6b 88 float SHT25::readHumidity(void)
YSI 7:b55223269e6b 89 {
YSI 7:b55223269e6b 90 char cmd[1] = {SHT_TRIG_RH_NHOLD}, rx[3] = {0xFF, 0xFF, 0xFF};
YSI 7:b55223269e6b 91 if(!_i2c.write(SHT_I2C_ADDR_WRITE, cmd, 1, false))
YSI 7:b55223269e6b 92 {
YSI 7:b55223269e6b 93 for(int i = 0; _i2c.read(SHT_I2C_ADDR_READ, rx, 3, false) && (i < 667); i++); //667*45ms(time to read at 400KHz) = 30ms(time max to measure RH on 12bit)
YSI 7:b55223269e6b 94 _selfHeatHumidity = false;
YSI 7:b55223269e6b 95 _h.attach(callback(this, &SHT25::keepSafeHumidity), SHT_SELF_HEATING);
YSI 7:b55223269e6b 96 return -6.0f + 125.0f * ((((rx[0] << 8) | rx[1]) & 0xFFFC) / 65536.0f);
YSI 7:b55223269e6b 97 }
YSI 7:b55223269e6b 98 return NAN;
YSI 7:b55223269e6b 99 }
YSI 7:b55223269e6b 100
YSI 5:8e34f365eb45 101 bool SHT25::setPrecision(const enum_sht_prec precision)
YSI 0:71da3fbfe141 102 {
YSI 7:b55223269e6b 103 char cmd[2] = {SHT_WRITE_REG_USER, precision};
YSI 7:b55223269e6b 104 return !_i2c.write(SHT_I2C_ADDR_WRITE, cmd, 2, false);
YSI 0:71da3fbfe141 105 }
YSI 0:71da3fbfe141 106
YSI 0:71da3fbfe141 107 bool SHT25::softReset()
YSI 0:71da3fbfe141 108 {
YSI 7:b55223269e6b 109 char cmd[1] = {SHT_SOFT_RESET};
YSI 7:b55223269e6b 110 return !_i2c.write(SHT_I2C_ADDR_WRITE, cmd, 1, false);
YSI 0:71da3fbfe141 111 }
YSI 0:71da3fbfe141 112
YSI 3:81324c19d870 113 void SHT25::waitSafeHeat(void)
YSI 3:81324c19d870 114 {
YSI 7:b55223269e6b 115 while(!_selfHeatTemperature || !_selfHeatHumidity) __NOP();
YSI 3:81324c19d870 116 }
YSI 3:81324c19d870 117
YSI 3:81324c19d870 118 void SHT25::keepSafeTemperature(void)
YSI 0:71da3fbfe141 119 {
YSI 3:81324c19d870 120 _selfHeatTemperature = true;
YSI 3:81324c19d870 121 }
YSI 3:81324c19d870 122
YSI 3:81324c19d870 123 void SHT25::keepSafeHumidity(void)
YSI 3:81324c19d870 124 {
YSI 3:81324c19d870 125 _selfHeatHumidity = true;
YSI 0:71da3fbfe141 126 }