SHT3x - Temp/Humd sensor

Temperature/humidity sensor using I2C bus.

Process flow

1 Wire.begin(): Initialize bus 2 .setup(): Initialize the sensor 3..begin(): Start operation of the sensor 4. 4.wait(): wait for a few ms 5..available()becomestrue 6. .get_temp(), .get_humid(): read values

Procedures required for operation

Wire bus

Before calling setup() method, Wire is put into operation by Wire.begin().

Procedures when returning from sleep mode

Keep the Wire bus in the operating state just before sleep (the Wire is automatically restored after sleep).

Code Example

#include <TWELITE>
#include <SNS_SHT3X>

SNS_SHT3X sns_sht3x; // Declaration of Objects

#include <SNS_SHT3X> and declaration of SNS_SHT3X class object is required.

Initialization

void setup() {
    Wire.begin();
    sns_sht3x.setup();
}

Start acquiring sensor values

void loop() {

  if(eState == E_STATE::INIT) {
    sns_sht3x.begin();
    eState = E_STATE::CAPTURE;
  }

}

Call .begin() to start acquiring sensor values. It takes several ms to complete.

In the above loop(), the process is designed to branch according to the state variable "eState". (Reference)

Waiting for sensor value acquisition

void loop() {

  if(eState == E_STATE::CAPTURE) {
    if (sns_sht3x.available()) {
      // Sensor value readout available
    }
  }

}

Whether the sensor value is ready or not can be determined by .available().

Reading sensor values

void loop() {

  if(eState == E_STATE::CAPTURE) {
    if (sns_sht3x.available()) {
      Serial << crlf << "SHT3X:"
            << " T=" << sns_sht3x.get_temp() << 'C'
						<< " H=" << sns_sht3x.get_humid() << '%';
    }
  }

}

As soon as the sensor value is ready, the value can be read out.

.get_temp(), get_humid() includes floating point operations; you can also get 100x integer values.

auto temp = div100(sns_sht3x.get_temp_cent());
auto humd = div100(sns_sht3x.get_humid_per_dmil);

Serial << crlf << "SHT3X:"
  << format(" T=%c%d.%02d", temp.neg ? '-' : ' ', temp.quo, temp.rem)
  << format(" T=%c%d.%02d", humd.neg ? '-' : ' ', humd.quo, humd.rem);

Here div100() is used to decompose 100x values into integer and decimal parts.

Methods

get_temp(), get_temp_cent()

double get_temp()
int16_t get_temp_cent()

Read temperature. get_temp() returns a value in °C and get_temp_cent() returns an integer value that is 100 times the value in °C.

On error, values between -32760 and -32768 are returned.

get_humid(), get_humid_per_dmil()

double get_humid()
int16_t get_humid_per_dmil()

Reads the humidity. get_humid() returns a value in %, and get_humid_per_dmil() returns an integer value of 100 times %.

On error, values between -32760 and -32768 are returned.

Common methods

setup()

void setup(uint32_t arg1 = 0UL) 

Allocates and initializes the memory area for the sensor.

The 8 bits from LSB of arg1 can store the I2C address. If not specified, leave it as 0.

#include <SNS_SHT3X>
SNS_SHT3X sns_sht3x;
bool b_found_sht3x = false;

void setup() {
 	sns_sht3x.setup();
	if (!sns_sht3x.probe()) {
		delayMicroseconds(100); // just in case, wait for devices to listen furthre I2C comm.
		sns_sht3x.setup(0x45); // alternative ID
		if (sns_sht3x.probe()) b_found_sht3x = true;
	} else {
		b_found_sht3x = true;
	}
}

In the above example, we first try to initialize with the default I2C ID, and if there is no response, we try to initialize with an address of 0x45.

begin(), end()

void begin()
void end()

Starts acquiring a sensor. It takes a few ms to read the value of the sensor and must wait until available() is true.

It does not support end().

process_ev()

void process_ev(uint32_t arg1, uint32_t arg2 = 0)

In the case of a sensor with wait processing, arg1 is given E_EVENT_TICK_TIMER or E_EVENT_START_UP to indicate the elapse of time. After calling this method, if the required time has elapsed, available() will be set to true and the sensor value can be read.

available()

bool available()

Returns true when the sensor satisfies the readout condition.

probe()

bool probe()

Returns true when the sensor is connected.

sns_stat()

uint32_t sns_stat()

Various information of the sensor device is stored.

• Stored values are undefined for this device.

sns_opt()

uint32_t& sns_opt()

The value passed in setup(uint32_t arg1) is stored.

• The lower 8 bits contain the address of the specified I2C device.