BME280 on the LoPy

[Devang Sharma]

@robd The first error you're getting is because of indentation of the return function. Write it within def humidity(self). I guess you're new to python, it'd be better if you read docs properly.

The second error is due to the way you've used import BME280. The library has a class BME280. There are 2 ways to solve this:

1. You can import it as from BME280 import * and make a constructor just after i2c something like this: bme = BME280(address=BME280_I2CADDR, i2c=i2c)

OR
2. keep it as import BME280 and constructor as:
bme = BME280.BME280(address=BME280_I2CADDR, i2c=i2c)

Make sure to use the same name as defined in the library.

I hope this helps you.

[robd]

@devang-sharma the code used was from https://github.com/LoRaWeather/BME280-LoPy-TTN/tree/master/Program/lib
I copied everything over as it was and didn't modify anything.
The code which I tried to write and didn't work was

from machine import I2C
import BME280
i2c = I2C(0,I2C.MASTER, baudrate=100000)

print('Temp = ', BME280.temperature())

Yes I am new to python and right now it is kicking me, I didn't see any docs other than small comments in the code. So it was me trying to feel around and get this sensor working.
I was able to get a SI7021(different code) to work but not the BME280.
I will look at and try to understand your suggestions.
Thank you for your help

[Devang Sharma]

@robd I think you didn't get me correctly.
Anyways, try the code as below:

from machine import I2C
import BME280
i2c = I2C(0,I2C.MASTER, baudrate=100000)
bme = BME280.BME280(address=BME280_I2CADDR, i2c=i2c)
print('Temp = ', bme.temperature())

[Lucas_Vieira]

Hello guys. i'm having similar problems here. Would you help me?

from machine import I2C
import bme280 # from bme280

i2c = I2C(0, I2C.MASTER)             # create and init as a master
i2c.init(I2C.MASTER, baudrate=10000) # init as a master
i2c.scan()
print(i2c.scan())
bmet = []   # Lista com as temperaturas lidas com o BME280
bmeh = []   # Lista com as umiadades lidas com o BME280
bmep = []   # Lista com as pressoes lidas com o BME280
bme = bme280.BME280(i2c=i2c, pressure_mode=bme280.OSAMPLE_8, iir=bme280.FILTER_8)
bme_s = True

while True:
    for cycles in range(10):
        # Le valores BME280 com media para ter maior precisao :
        numreadings = 5
        samples_temperature = [0.0]*numreadings; mean_temperature = 0.0
        samples_pressure = [0.0]*numreadings; mean_pressure = 0.0
        samples_humidity = [0.0]*numreadings; mean_humidity = 0.0
        for i in range (numreadings):
            samples_temperature[i], samples_pressure[i], samples_humidity[i] = bme.values
        mean_temperature = sum(samples_temperature)/len(samples_temperature)
        mean_pressure = sum(samples_pressure)/len(samples_pressure)
        mean_humidity = sum(samples_humidity)/len(samples_humidity)
        t = mean_temperature
        p = mean_pressure/101325   # Pa -> hectoPa
        h = mean_humidity
        bmet.append(t)
        bmep.append(p)
        bmeh.append(h)

    print(t)
    print(p)
    #print(h)
    time.sleep(3)

My problems:

File lib bme280:
bme280.py

[svonbentzel]

@Lucas_Vieira i2c.scan() reports the correct sensor? 108 (I mean)??

[svonbentzel]

@Lucas_Vieira

Do you have tried the other modes?
The sensor is correct wired? Sda / p9 and scl p10 in example?

[Lucas_Vieira]

@svonbentzel thank you very much for reply!

1. i2c.scan() report: [118]
2. What modes are they? I did not understand what you meant.
3. Yes, the pins are correct!

Note: Right now, it's running perfect. No more errors appear in the code, it is strange at least hahaha. However, since yesterday I have not received any sign of humidity, is there any clue where the error is? I can not find.
(I uncommented "print (h)" in the last code).

The image data is pressure (1.0), temperature (27ºC) and humidity (0.0) respectively.

[robert-hh]

@Lucas_Vieira The value for pressure is also strange. The class function values returns Pascal, so the expected numbers are in the range of 100000.
You may also try my variations of the adafruit driver. Most of the BME280 drivers I have seen are based on that. You may have to change values(), to return t,p,h instead of formatted strings. I used that driver a lot with pycom devices and it worked well. The sensors I used were sometimes out of range.
https://github.com/robert-hh/BME280
There are two variants, which differn from the mode of internal calculations (float or int). The results are comparable.

[Lucas_Vieira]

@robert-hh
Hi Robert.

1. The pressure value is strange because I had converted to ATM. But I returned to normal, getting the value in Pascal.
2. can't your drive receive temperature, pressure and humidity values ​​separately? I need to send the data to my cayenne application.

I am having these cayenne LPP errors. Can you help me? I need to open a new post or we can keep talking on this I2C topic, maybe it could be wrong?

[robert-hh]

@Lucas_Vieira Yes, just change the last line of the method values() to:
return t, p, h
I never had sent values directly to cayenne, only through TTN. Which cayenne LPP module are you using?

Edit: In my tests, the value for humidity was the one with the largest error, but still not 0. Are you sure that you have a BME280 device and not an BMP280? If you look at the package, there are two lines of letters
BME280:
xxx
Ux
BMP280:
xxx
Kx
The difference is U vs. K