Could I also ask you to point me in a direction for the calibration formula or a small description of the theory behind calibrating it ? in my head I just feel like chopping 3 degrees off the reading would almost suffice, but Im sure there is a more eloquent method. Ultimately if I can figure it out, sleeping code will be needed for longer run times in terms of battery longevity. This seemingly also would help a bit with accurate temps.

Thanks!

The sensors have been proved not to be fully realible and need calibrating, tuning in code in order to work in the environment you intend them to work in.

As to the I2C address issue. If you have more than 1 device on the bus with the same i2c address, the data received by the sticks could be corrupted, the bus may stop working or data recorded will be very inaccurate.

I did start to understand the 0x56 addresse and 0x44 I think it is.. it seems like the addresses were the same in the technical manuals, but maybe that has no bearing on what you are saying ?
Im guessing the wire. commands Im seeing would be for the non hat version ?

Ill start looking for the difference in the pins and maybe be able to learn something again!

Again, Im a super newb and I appreciate the help.

I originally found this thread because my envIII hat temperature reading just cant be true. it seems a bit high and sort of climbs at time and peaks around 29 degrees. I suspect its the working temperature of the M5stick. screen heat I guess?

ENVIII uses the port on the bottom of the stick whereas the HAT use the pins on the top of the stick.

Im a newb, but sort of know what Im looking at with this code.

But Im unable to get this running on my M5stickCplus with ENVIII
even with the help for ENVIII in the code the // comments I cant get this working. I get the screen blink every 30 seconds, which I dialed down to ten seconds, and it blinks no readings, all at 0.00

What am I missing here? I also couldnt find M5_env.h and used m5stack_ENV.h from the install libraries, assuming they are the same ?

Thanks for any help. Especially thanks to the OP for his code here, looks promising, helping me learn a lot.

Unfortunately I misplaced the manual, but I did find this summary doc online. It states the following features:

• Accuracy : -20-100°C +/- 1°C
• Resolution : 0.1°C

Nevertheless, I have a couple of DS18B20 sensors, which are known to be pretty accurate, all of which indicate a temperature very close to that measured by my kitchen thermometer.

An error close to 1°C is acceptable in my use case, but ENV II or ENV III HATs get worse measurements than my DS18B20. I also compared these measurements with other sensors like the Adafruit BME280 (which always gives measurements with a 2°C increase because of the voltage regulator on the sensor board), but which is still accurate when taken into account.

Thank you,
Steph

ENV II even has two temperature sensors, since instead of the QMP6988, it has a BMP280, which is a pressure and temperature sensor. It is, therefore, possible to perform 2 simultaneous temperature measurements!

So, this time things work better:

We still notice a difference in the temperature measurements. The SHT30 seems to get better results (which is probably why they added it).

Here, it's still 1°C above the real temperature. In the meantime, I turned on the air-conditioning, so maybe the deviation is reduced because of the ventilation? On the other hand, we can see that the temperature measured by the BMP280 is 1°C higher than the one measured by the SHT30.

But this time, I get a non-zero pressure measurement. 🙂

Here is the new version of my code for those who are interested:

#include <M5Unified.h>
#include <UNIT_ENV.h>
#include <Adafruit_BMP280.h>

constexpr uint32_t SLEEP_DURATION_US = 30 * 1000 * 1000; // 30 sec

SHT3X sht30;
Adafruit_BMP280 bmp;
// QMP6988 qmp6988; // only for ENV III

void setup() {

    M5.begin();
    M5.Display.setRotation(3);
    M5.Display.setFont(&fonts::Font2);

    Wire.begin(0, 26);
    bmp.begin(0x76);
    bmp.setSampling(
        Adafruit_BMP280::MODE_NORMAL,
        Adafruit_BMP280::SAMPLING_X16,
        Adafruit_BMP280::SAMPLING_X16,
        Adafruit_BMP280::FILTER_X16,
        Adafruit_BMP280::STANDBY_MS_500
    );

    // qmp6988.init(); // only for ENV III
    
}

void displayMeasurement(
    const uint8_t x1,
    const uint8_t x2,
    const uint8_t x3,
    const uint8_t y,
    const char*   sensor,
    const char*   data,
    const float_t value
) {

    M5.Display.drawString(sensor,  x1, y);
    M5.Display.drawString(data,    x2, y);
    M5.Display.drawFloat(value, 2, x3, y);

}

void loop() {

    static float_t temperature_1, temperature_2, humidity, pressure;

    uint8_t fail = sht30.get();

    temperature_1 = bmp.readTemperature();
    temperature_2 = fail ? 0 : sht30.cTemp;
    humidity      = fail ? 0 : sht30.humidity;
    pressure      = bmp.readPressure();
    
    // only for ENV III
    // pressure = qmp6988.calcPressure();
    // qmp6988.setpPowermode(QMP6988_SLEEP_MODE);

    displayMeasurement(10, 70, 100, 10, "BMP280", "T1", temperature_1);
    displayMeasurement(10, 70, 100, 30, "SHT30",  "T2", temperature_2);
    displayMeasurement(10, 70, 100, 50, "SHT30",  "H",  humidity);
    displayMeasurement(10, 70, 100, 70, "BMP280", "P",  pressure);

    delay(2000);
    
    M5.Power.deepSleep(SLEEP_DURATION_US);

}

Sorry for my confusion between ENV II and ENV III. But maybe finally the questions raised here will be useful to some readers...

    // M5.Power.Axp192.setLDO2(0);
    // esp_sleep_enable_timer_wakeup(SLEEP_DURATION_US);
    // esp_deep_sleep_start();
    M5.Power.deepSleep(SLEEP_DURATION_US);

But I still have a 2.5°C difference...

On the other hand, I don't have a solution for the pressure measurement. 😕