SI7021

• Use with Raspberry Pi
• Requires lgpio
• Code tested inside virtual Raspberry Pi Zero/3/4 environments on GitHub

Example

#include "SI7021.h"
#include <iostream>

int main() {

    SI7021::SI7021 sensor;

    //connect to and initialise the sensor
    sensor.connect();

    //obtain new temperature and humidity readings
    sensor.refresh();

    std::cout 
        << "Temperature: "
        << sensor.getTemperature() << " C, "
        << "Humidity: "
        << sensor.getHumidity() << " %RH"
        << std::endl;

    //prints eg.
    //Temperature: 16.0205 C, Humidity: 62.8667 %RH

    return 0;

}

Documentation

• SI7021( int dev, int addr ). Constructor taking dev identifying which I2C device to use (default is device 1), and addr identifying which I2C address to use (default is 0x40).

• void connect( ). Setup and connect to the device.

• void disconnect( ). Disconnect from the device.

• void refresh( ). Get a humidity and temperature sample from the sensor.

• double getTemperature( ). Returns the last read temperature in degrees celsius.

• double getHumidity( ). Returns the last read relative humidity as a percentage.

• void reset( ). Reset the device.

• void resetSettings( ). Reset UserRegister1 register (ie. measurement resolution and heater status) and HeaterControlRegister register (ie. heater power).

• std::uint8_t getMeasurementResolution( ). Returns the measurement resolution from the device, between 0 and 3.

• void setMeasurementResolution( std::uint8_t res ). Sets the measurement resolution, between 0 and 3.

• VddStatus getVddStatus( ). Returns VddStatus::OK if voltage level is sufficient, otherwise VddStatus::LOW.

• HeaterStatus getHeaterStatus( ). Returns HeaterStatus::ENABLED if the heater is enabled, or HeaterStatus::DISABLED if disabled.

• void setHeaterStatus( HeaterStatus status ). Enable or disable the heater.

• std::uint8_t getHeaterPower( ). Returns the heater power, between 0 and 15.

• void setHeaterPower( std::uint8_t power ). Set the heater power, between 0 and 15.

• SerialNumber getSerialNumber( ). Gets the serial number of the device. SerialNumber is a typedef for a std::uint64_t.

• DeviceId getDeviceId( ). Gets the device id.

identifier	description	devIdToString
DeviceId::ENG_SAMPLE_1	engineering sample	engineering sample
DeviceId::ENG_SAMPLE_2	engineering sample	engineering sample
DeviceId::SI7013	SI7013	Si7013
DeviceId::SI7020	SI7020	Si7020
DeviceId::SI7021	SI7021	Si7021
DeviceId::UNKNOWN	unknown device	unknown

• FirmwareRevision getFirmwareRevision( ). Gets the device firmware revision.

identifier	description	fwRevToString
FirmwareRevision::REV_1_0	revision 1.0	1.0
FirmwareRevision::REV_2_0	revision 2.0	2.0
FirmwareRevision::UNKNOWN	unknown firmware	unknown

• const char* const devIdToString( DeviceId id ). Returns a C string representing the device id.

• const char* const fwRevToString( FirmwareRevision rev ). Returns a C string representing the firmware revision.