BME280 on the LoPy

[sakis]

@livius

Hi Livius,

Can you give an example of the minimum code to reproduce this issue (preferably on GitHub)?

[livius]

@sakis
I will try to minimize code but i can't promise that this will be today

but you can try @binux sample (i did not tried it self) - maybe this is minimal code to reproduce.

[livius]

@sakis
I see that I2C work back in 1.6.9 :)

[Butch]

@binux I am seeing exactly the same problem with 1.6.10b1. I have Vin on the BME280 tied to 3.3v on the LoPy, I have ground on the BME280 tied to gnd on the LoPy, I have SDA on the BME280 tied to pin P9 on the LoPy, and I have SCL on the BME280 tied to pin P10 on the LoPy.

>>> from machine import I2C
>>> import bme280
>>> i2c = I2C(0, I2C.MASTER, baudrate=100000)
>>> i2c.scan()
[118]
>>> bme = bme280.BME280(i2c=i2c)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "bme280.py", line 186, in __init__
  File "bme280.py", line 192, in _load_calibration
  File "bme280.py", line 152, in readU16LE
  File "bme280.py", line 135, in readU16
OSError: I2C bus error

As you can see, the I2C bus has something on it at hex address 0x76 (118 decimal). However, initializing the BME280 fails.

Any help, anyone? Please?

Thanks!

[RobTuDelft]

You have to specifiy the address when creating the sensor object:
def __init__(self, address, i2c):. I don't see the address getting the default address assigned here, maybe that's your issue?

edit:
I was looking at the wrong class
address=BME280_I2CADDR

It gets the default address from there
self._device = Device(address, i2c)

[ledbelly2142]

I am trying to use the same library with a BME280 and am experienceing the exact same issue with firmware version 1.7.4.b1
same error:

Traceback (most recent call last):                                                                                      
  File "main.py", line 9, in <module>                                                                                   
  File "bme280.py", line 198, in init                                                                               
  File "bme280.py", line 204, in _load_calibration                                                                      
  File "bme280.py", line 164, in readU16LE                                                                              
  File "bme280.py", line 147, in readU16  

Did anyone get this to work?

[Butch]

@ledbelly2142 said in BME280 on the LoPy:

I am trying to use the same library with a BME280 and am experienceing the exact same issue with firmware version 1.7.4.b1
same error:

Traceback (most recent call last):                                                                                      
  File "main.py", line 9, in <module>                                                                                   
  File "bme280.py", line 198, in init                                                                               
  File "bme280.py", line 204, in _load_calibration                                                                      
  File "bme280.py", line 164, in readU16LE                                                                              
  File "bme280.py", line 147, in readU16  

Did anyone get this to work?

Try my fork of the library: https://github.com/ButchAnton/LoPy_BME280

[ledbelly2142]

@Butch
yup, thats what I'm using. I forked it. Why the init.py file?

[Butch]

@ledbelly2142 That makes it into a package: https://docs.python.org/2/tutorial/modules.html#packages

[ledbelly2142]

@Butch
I still have the same issue, just updated to the latest firmware 1.7.5.b2
In the main.py I'm just trying to print out values in the console, I have:

import pycom
from machine import I2C
import time
import bme280 # from bme280

i2c = I2C(0, I2C.MASTER, baudrate=100000)
i2c.scan()
#i2c = machine.I2C(0, pins=('GP11', 'GP10'))
bme = bme280.BME280(i2c=i2c)

pycom.heartbeat(False)

temp = BME280.temperature()
humid = BME280.humidity()
press = BME280.pressure()
alti = BME280.altitude()

#for cycles in range(10): # stop after 10 cycles
while(true):
    print(temp) # read temperature
    time.sleep(2)
    print(humid) # read humidity
    time.sleep(2)
    print(press) # read Pressure
    time.sleep(2)
    print(alti) # read altitude
    time.sleep(2)

[Butch]

@ledbelly2142 Try following the line of logic I tried in the python REPL: import, instantiate, and initialize:

>>> from machine import I2C
>>> import bme280
>>> i2c = I2C(0, I2C.MASTER, baudrate=100000)
>>> bme = bme280.BME280(i2c=i2c)

See where that takes you.

The original problem I ran into and ultimate fixed was that the 8- and 16-bit writes needed the value to be written to be a bytearray, not the raw value. Beyond that, all I added was a wrapper for altitude.

[ledbelly2142]

@Butch

For me, the issue comes up from :
bme = bme280.BME280(i2c=i2c)

Thats where I get the errors indicating an I2C bus error.

I SDA on pin 9 and SCL on pin 10.

Could it be a bad sensor?

So I unplugged the BME280 sensor and got the same error.

[Butch]

@ledbelly2142 It's possible that it's a bad sensor. Do you have another one to try? You might also check to make sure that i2c.scan() is returning the same address that is used in the BME280 library. If it isn't, you'll have to change the address in the library.

[ledbelly2142]

@Butch
That looks to be it. The I2C address was 77, not 76... weird. I did not think to check the I2C address.

Thanks!

[Devang Sharma]

Hello Everyone,
I'm using LoPy and I've got the similar type of error as @binux got.

I'm getting the following error:

This is my code:

Please guide me solving this!
Thank You.

[robert-hh]

@devang-sharma The required positional argument is 'little' in the call of from_bytes(). The API was changed a while ago. You have to modify the script BM280.py into:

        result = int.from_bytes(
            self._i2c.readfrom_mem(self._address, register, 2), little) & 0xFFFF

The same in function readU8().

[Devang Sharma]

@robert-hh I've done changes as you said but got the NameError as:

"name 'little' is not defined". How can I solve it?
Thank You.

[robert-hh]

@devang-sharma Sorry, it should be a string:

        result = int.from_bytes(
            self._i2c.readfrom_mem(self._address, register, 2), 'little') & 0xFFFF

[Devang Sharma]

@robert-hh, that worked! Thanks, but the same error for write8:

Is there any link to the changed API or library? That would be better than posting every single error! :'D

EDIT: Solved the error. Replaced value.to_bytes(1) with "value"! No more Errors!

[robert-hh]

@devang-sharma No specific API doc needed, since it is standard Python behaviour now. It was incompatible before, but I'm not shure, for which MicroPython version. It may be that the Pycom branch always was compatible to the Standard.
And yes, even in that case changes toward language compliance may break code, so it should be noted.