esp32-sensornode/main/si7021.cpp

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/*
* si7021 library
* SI7021 Temperature and Humidity Sensor @ ESP32 i2c
*
* copyright: Jannik Beyerstedt | http://jannikbeyerstedt.de | code@jannikbeyerstedt.de
* license: http://www.gnu.org/licenses/gpl-3.0.txt GPLv3 License
*/
#include <Arduino.h>
#include <Wire.h>
#include "si7021.hpp"
/**
* Constuctor of the SI7021 sensor wrapper
*/
Si7021::Si7021(void) {
_i2caddr = SI7021_DEFAULT_ADDRESS;
}
/**
* Start the I2C interface
* Attention: leave at least 25 ms power up time before the first measurement
*/
bool Si7021::begin(void) {
Wire.begin();
Wire.setClock(200000);
reset();
if (readRegister8(SI7021_READRHT_REG_CMD) != 0x3A) {
return false;
}
return true;
}
/**
* Send a reset command to the sensor
*/
void Si7021::reset(void) {
Wire.beginTransmission(_i2caddr);
Wire.write((uint8_t)SI7021_RESET_CMD);
Wire.endTransmission(true);
delay(10); // SI7021 reset time
}
/**
* Initiate a humidity and temperature measurement
* Get the values from the public variables temperature and humudity
*
* @return true, if successful measurement
*/
bool Si7021::measure(void) {
uint8_t chxsum;
uint8_t cnt;
// TRIGGER HUMIDITY MEASUREMENT AND GET VALUE
Wire.beginTransmission(_i2caddr);
Wire.write((uint8_t)SI7021_MEASRH_NOHOLD_CMD);
Wire.endTransmission(true); // true, otherwise the read will not work
delay(23); // wait for the Conversion Time of the Sensor
cnt = Wire.requestFrom(_i2caddr, 3);
if (cnt < 3) {
// Serial.printf("[ERROR] SI7021 humi, only %d bytes received\n", cnt);
return false;
}
uint16_t hum_raw = Wire.read();
hum_raw <<= 8;
hum_raw |= Wire.read();
chxsum = Wire.read();
this->humidity = hum_raw;
this->humidity *= 125;
this->humidity /= 65536;
this->humidity -= 6;
// GET TEMPERATURE VALUE OF PREVIOUS HUMIDITY MEASUREMENT
Wire.beginTransmission(_i2caddr);
Wire.write((uint8_t)SI7021_READPREVTEMP_CMD);
Wire.endTransmission(true); // true, otherwise the read will not work
cnt = Wire.requestFrom(_i2caddr, 3);
if (cnt < 3) {
// Serial.printf("[ERROR] SI7021 temp, only %d bytes received\n", cnt);
return false;
}
uint16_t temp_raw = Wire.read();
temp_raw <<= 8;
temp_raw |= Wire.read();
chxsum = Wire.read();
this->temperature = temp_raw;
this->temperature *= 175.72;
this->temperature /= 65536;
this->temperature -= 46.85;
return true;
}
// void Si7021::writeRegister8(uint8_t reg, uint8_t value) {
// // TODO: Test
// Wire.beginTransmission(_i2caddr);
// Wire.write((uint8_t)reg);
// Wire.write((uint8_t)value);
// Wire.endTransmission();
// }
uint8_t Si7021::readRegister8(uint8_t reg) {
uint8_t value;
Wire.beginTransmission(_i2caddr);
Wire.write((uint8_t)reg);
Wire.endTransmission(true); // true, otherwise the value does not get read
Wire.requestFrom(_i2caddr, 1);
value = Wire.read();
return value;
}