Pico GFX Pack BME68x demo

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1

OK I have a PicoW, a GFXPack and a BME688 (PIM575) breakout.
The demo code is:
micropython/examples/gfx_pack/thermometer.py.

import time
import machine
from gfx_pack import GfxPack
from breakout_bme68x import BreakoutBME68X, STATUS_HEATER_STABLE

"""
GFX temp DEMO

This demo uses a BME680 or BME688 attached to the QWST connector to
measure temperature, pressure, and humidity and display it on the GFX display,
or the internal temperature sensor can be used in place of the
BME68x breakout. Just change use_bme68x_breakout to False
"""

# Settings
lower_temp_bound = 15
upper_temp_bound = 30
use_bme68x_breakout = True

sensor_temp = machine.ADC(4)
conversion_factor = 3.3 / (65535)  # used for calculating a temperature from the raw sensor reading

gp = GfxPack()
gp.set_backlight(0, 0, 0)  # turn the RGB backlight off
display = gp.display
display.set_backlight(0.4)  # set the white to a low value

if use_bme68x_breakout:
    bmp = BreakoutBME68X(gp.i2c)

display.set_pen(0)
display.clear()
display.set_font("bitmap14_outline")

while True:
    # Clear display
    display.set_pen(0)
    display.clear()

    display.set_pen(15)
    display.text("GFXPack Temp demo", 0, 0, scale=0.1)

    if use_bme68x_breakout:
        temperature, pressure, humidity, gas, status, _, _ = bmp.read()
        display.text("Temp: {:0.2f}c".format(temperature), 0, 20, scale=0.2)
        display.text("Press: {:0.2f}Pa".format(pressure), 0, 35, scale=0.2)
        display.text("Humid: {:0.2f}%".format(humidity), 0, 50, scale=0.2)

        heater = "Stable" if status & STATUS_HEATER_STABLE else "Unstable"
        print("{:0.2f}c, {:0.2f}Pa, {:0.2f}%, {:0.2f} Ohms, Heater: {}".format(
            temperature, pressure, humidity, gas, heater))

    else:
        reading = sensor_temp.read_u16() * conversion_factor
        temperature = 27 - (reading - 0.706) / 0.001721
        display.text("Temperature", 25, 15, scale=0.2)
        display.text("{:0.2f}c".format(temperature), 25, 30, scale=2)

    if temperature < lower_temp_bound:
        r = 0
        b = 255
    elif temperature > upper_temp_bound:
        r = 255
        b = 0
    else:
        r = (temperature - lower_temp_bound) / (upper_temp_bound - lower_temp_bound) * 255
        b = 255 - ((temperature - lower_temp_bound) / (upper_temp_bound - lower_temp_bound) * 255)

    gp.set_backlight(r, 0, b)
    display.update()

    time.sleep(0.2)

Question 1. How do I insert a degree symbol (Unicode U+00B0)?
Question 2. How do I display pressure as hPa (which is what is used in barometers)?
Question 3. How do I display the air quality from the BME688?
Question 4. How do I correct pressure for sea level?
Question 5. How do I get a more accurate temperature reading (readings at off by +2 degC)?

Thanks
Andrew

2

Not sure what your issue is, based on what you posted?
Code tags are the </> button, (preformatted text).
That will retain your code indents etc.

The BME example may need to be edited so it is using the correct i2c pins.

3

I hope my edited post now makes sense. The interface didn’t recognise some of what I pasted as code! After a bit of trial and error it does now.

4

For question one, have a look at this.
Display the degree character in Micro python? - Discussion - Pimoroni Buccaneers

For me its mb and I just divide the Pa by 100.
pressuremb = pressure / 100

Have a look at this example for the Pico Enviro+
It has code for gas readings, correction for MSL, and temperature compensation.
pimoroni-pico/micropython/examples/pico_enviro/enviro_all.py at main · pimoroni/pimoroni-pico (github.com)