BME280 telemetry data

[memo-567]

I tried to use the telemetry data from a BME280 connected to the Heletec V3. Unfortunately, it appears that only the smartphone's sensors are taken into account. Or did I configure something incorrectly somewhere?

[memo-567]

My aim is to use the sensor (or better the BME680) via the Raspberry (currently with MeshChat).

[markqvist]

Currently, Sideband can only pull telemetry data from something that's directly connected to the host. Here's an example plugin for doing that:

https://github.com/markqvist/Sideband/blob/main/docs/example_plugins/telemetry.py

That being said, all that's needed for sensors connected to the RNode to be taken into account is simply to add the necessary sensor driver to the firmware, and a shim that sends that data to Sideband over whatever connection is used between the Sdieband host and the RNode.

It's not really a big hassle, it just isn't implemented yet.

[memo-567]

This is beyond my skills and knowledge. I then wait a bit until it is implemented in RNode.
Thanks for the info.

[memo-567]

I have now connected the BME280 to the Raspberry and, after I have installed the necessary libraries, I can call an (already existing) script that reads the data.
Now I just need to have this data written to one of the example telemetry plugins when the script is called and then it would be done.
Let's see if I can maybe (!) manage that too, because I don't know Python at all ¯\(ツ)/¯

[markqvist]

I provided some pointers in an example below :)

[markqvist]

Here's a skeleton example to implement a BME280 telemetry plugin:

# This is a BME280 telemetry plugin
# example that you can build upon to
# implement your own telemetry plugins.

import RNS

class BME280Plugin(SidebandTelemetryPlugin):
    plugin_name = "telemetry_bme280"

    def start(self):
        # Do any initialisation work here
        RNS.log("BME280 telemetry plugin starting...")

        # And finally call start on superclass
        super().start()

    def stop(self):
        # Do any teardown work here
        pass

        # And finally call stop on superclass
        super().stop()

    def update_telemetry(self, telemeter):
        if telemeter != None:
            
            # Create temperature sensor
            telemeter.synthesize("temperature")
            telemeter.sensors["temperature"].data = {"c": 23.6}

            # Create humidity sensor
            telemeter.synthesize("humidity")
            telemeter.sensors["humidity"].data = {"percent_relative": 52.1}

            # Create humidity sensor
            telemeter.synthesize("pressure")
            telemeter.sensors["pressure"].data = {"mbar": 1011.2}


# Finally, tell Sideband what class in this
# file is the actual plugin class.
plugin_class = BME280Plugin

Currently it just sets the values statically, but it will get you something like this:

You will just need to add some way of setting the values from the actual BME280 instead of the example values.

You can read from I2C devices directly in Python by using the smbus2 module. Install with pip install smbus2. It's very easy to use, and works out of the box on Raspberry Pi, when installed via pip.

[markqvist]

There's additional data for reading data from the BME280 specifically using Python and RasPi here:

https://randomnerdtutorials.com/raspberry-pi-bme280-data-logger/

[memo-567]

Oh, thank you. I'm going to test that right away 😀

[memo-567]

Making two scripts into one 😆
I finally managed it. The modified script works, after a lot of testing and a little logic.

# This is a BME280 telemetry plugin
# example that you can build upon to
# implement your own telemetry plugins.

import RNS
import smbus2
import bme280

# BME280 sensor address (default address)
address = 0x76

# Initialize I2C bus
bus = smbus2.SMBus(1)

# Load calibration parameters
calibration_params = bme280.load_calibration_params(bus, address)

# Read sensor data
data = bme280.sample(bus, address, calibration_params)

# Extract temperature, pressure, humidity
temperature = round(data.temperature,1)
humidity = round(data.humidity,1)
pressure = round(data.pressure,1)       
        

class BME280Plugin(SidebandTelemetryPlugin):
    plugin_name = "telemetry_bme280"

    def start(self):
        # Do any initialisation work here
        RNS.log("BME280 telemetry plugin starting...")

        # And finally call start on superclass
        super().start()

    def stop(self):
        # Do any teardown work here
        pass

        # And finally call stop on superclass
        super().stop()

    def update_telemetry(self, telemeter):
        if telemeter != None:
            
            # Create temperature sensor
            telemeter.synthesize("temperature")
            telemeter.sensors["temperature"].data = {"c": temperature}

            # Create humidity sensor
            telemeter.synthesize("humidity")
            telemeter.sensors["humidity"].data = {"percent_relative": humidity}

            # Create humidity sensor
            telemeter.synthesize("pressure")
            telemeter.sensors["pressure"].data = {"mbar": pressure}


# Finally, tell Sideband what class in this
# file is the actual plugin class.
plugin_class = BME280Plugin

[markqvist]

Awesome! Looking great! You probably want to make sure the plugin updates the values from the BME280 each time the update_telemetry function runs.

[memo-567]

Thanks. Today it was the first time I've worked with Python, and it was almost entirely trial and error. And a little logic.
If I'm (perhaps) seeing this correctly, then the section

# Read sensor data
data = bme280.sample(bus, address, calibration_params)

# Extract temperature, pressure, humidity
temperature = round(data.temperature,1)
humidity = round(data.humidity,1)
pressure = round(data.pressure,1)    

should be placed directely behind

    def update_telemetry(self, telemeter):
        if telemeter != None:

?

[memo-567]

Although I don't know if that's correct now, that's how the plugin works ¯\__(ツ)__/¯

# This is a BME280 telemetry plugin
# example that you can build upon to
# implement your own telemetry plugins.

import RNS
import smbus2
import bme280

# BME280 sensor address (default address)
address = 0x76

# Initialize I2C bus
bus = smbus2.SMBus(1)



# Load calibration parameters
calibration_params = bme280.load_calibration_params(bus, address)

# Read sensor data
data = bme280.sample(bus, address, calibration_params)

# Extract temperature, pressure, humidity
temperature = round(data.temperature,1)
humidity = round(data.humidity,1)
pressure = round(data.pressure,1)       
        

class BME280Plugin(SidebandTelemetryPlugin):
    plugin_name = "telemetry_bme280"

    def start(self):
        # Do any initialisation work here
        RNS.log("BME280 telemetry plugin starting...")

        # And finally call start on superclass
        super().start()

    def stop(self):
        # Do any teardown work here
        pass

        # And finally call stop on superclass
        super().stop()

    def update_telemetry(self, telemeter):
        if telemeter != None:
            
            # Read sensor data
            data = bme280.sample(bus, address, calibration_params)
            
            # Extract temperature, pressure, humidity
            temperature = round(data.temperature,1)
            humidity = round(data.humidity,1)
            pressure = round(data.pressure,1)   
            
            # Create temperature sensor
            telemeter.synthesize("temperature")
            telemeter.sensors["temperature"].data = {"c": temperature}

            # Create humidity sensor
            telemeter.synthesize("humidity")
            telemeter.sensors["humidity"].data = {"percent_relative": humidity}

            # Create humidity sensor
            telemeter.synthesize("pressure")
            telemeter.sensors["pressure"].data = {"mbar": pressure}


# Finally, tell Sideband what class in this
# file is the actual plugin class.
plugin_class = BME280Plugin

[markqvist]

Here's an updated version with a bit better init/teardown and error handling added:

# This plugin provides temperature, humidity
# and pressure data via a BME280 sensor
# connected over I2C. The plugin requires
# the "smbus2" and "RPi.bme280" modules to
# be available on your system. These can be
# installed with:
#
# pip install smbus2 RPi.bme280

import os
import RNS
from importlib.util import find_spec

class BME280Plugin(SidebandTelemetryPlugin):
    plugin_name = "telemetry_bme280"

    I2C_ADDRESS = 0x76
    I2C_BUS     = 1

    def start(self):
        RNS.log("BME280 telemetry plugin starting...")

        if find_spec("smbus2"): import smbus2
        else: raise OSError(f"No smbus2 module available, cannot start BME280 telemetry plugin")
        
        if find_spec("bme280"): import bme280
        else: raise OSError(f"No bme280 module available, cannot start BME280 telemetry plugin")

        self.sensor_connected = False

        try:
            self.bme280 = bme280
            self.address = self.I2C_ADDRESS
            self.bus = smbus2.SMBus(self.I2C_BUS)
            self.calibration = self.bme280.load_calibration_params(self.bus, self.address)
            self.sensor_connected = True
        
        except Exception as e:
            RNS.log(f"Could not connect to I2C device while starting BME280 telemetry plugin", RNS.LOG_ERROR)
            RNS.log(f"The contained exception was: {e}", RNS.LOG_ERROR)

        super().start()

    def stop(self):
        self.bus.close()
        super().stop()

    def update_telemetry(self, telemeter):
        if telemeter != None:
            if self.sensor_connected:
                try:
                    sample = self.bme280.sample(self.bus, self.address, self.calibration); ts = telemeter.sensors
                    telemeter.synthesize("temperature"); ts["temperature"].data = {"c": round(sample.temperature,1)}
                    telemeter.synthesize("humidity");    ts["humidity"].data    = {"percent_relative": round(sample.humidity,1)}
                    telemeter.synthesize("pressure");    ts["pressure"].data    = {"mbar": round(sample.pressure,1)}

                except Exception as e:
                    RNS.log("An error occurred while updating BME280 sensor data", RNS.LOG_ERROR)
                    RNS.log(f"The contained exception was: {e}", RNS.LOG_ERROR)

plugin_class = BME280Plugin

I didn't actually try running this yet on a Pi, so there might be something wrong, but feel free to try it out!

[memo-567]

Good morning Mark.
No, unfortunately the plugin does not show any data here. Where, if available, is the log file stored?

[markqvist]

Must have messed somethign up then ;)

You can watch the debug log output by launching Sideband from a terminal with sideband -v, or by going to "Utilities -> Debug log viewer" within Sideband.

[memo-567]

[markqvist]

Doh! I forgot to reference the bme280 class in the plugin instance ;) I've updated the code I posted above.

[memo-567]

This works perfect now 👍

[markqvist]

Good to hear!

[memo-567]

By the way:
I added another variable so that the deviations that exist in almost every BME280 can be compensated for.

# Custom BME 280 deviation
temp_diff = 0.0
.
.
.
.
            # Extract temperature, pressure, humidity
            temperature = round(data.temperature - temp_diff,1)
            humidity = round(data.humidity,1)
            pressure = round(data.pressure,1)   

However, I couldn't manage to turn the "c" into a "°C".

[markqvist]

I added another variable so that the deviations that exist in almost every BME280 can be compensated for.

Great idea!

However, I couldn't manage to turn the "c" into a "°C".

That's just a rendering thing in Sideband. The degree symbol is not included in the data itself of course, it's up to the application to render that. I guess I can add that in the next update to Sideband.