Wipy 2.0 and BME280 sensor

[michal]

Hello!

Was anybody able to use I2C BME280 sensor? It works flawlessly on Wipy 1.0 using a driver from Paul Cunnane (https://bitbucket.org/oscarBravo/wipy_bme280), but I get strange errors on Wipy 2.0:

>>> from machine import I2C
>>> import bme280
>>> i2c = I2C(0, I2C.MASTER, baudrate=100000)
>>> bme = bme280.BME280(i2c=i2c)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/flash/lib/bme280.py", line 186, in __init__
  File "/flash/lib/bme280.py", line 106, in write8
TypeError: object with buffer protocol required

It looks like this operation fails:
i2c.writeto_mem(0x76, 0xF4, 0x3F)

I can see the device on I2C bus, so the wiring should be OK. I also have a HD44780 display with PCF8574 backpack connected to I2C bus and it works.

I am using the latest firmware 0.9.4b1.

One last thing - I am connected to Wipy via telnet (Putty) and the REPL is almost unusable. After few lines of code it hangs or key presses start to generate weird characters.

Michal

[daniel]

@michal when you do the i2c.scan() are you able to see the sensor connected?

TypeError: object with buffer protocol required

This error occurs because the function expects a bytes object and you are trying to send an integer. Could you try with:

i2c.writeto_mem(0x76, 0xF4, bytes([0x3F]))

?

Obviously we should make the drivers fully compatible with the old ones. We'll definitely fix it, but please try the workaround above to confirm the problem. Thanks.

Cheers,
Daniel

[michal]

Hi Daniel!

I can confirm, that it works with bytes object:-)

>>> from machine import I2C
>>> import bme280
>>> i2c = I2C(0, I2C.MASTER, baudrate=100000)
>>> bme = bme280.BME280(i2c=i2c)
>>> print(bme.temperature, bme.pressure, bme.humidity)
24.07C 967.63hPa 64.16%

I got confused with I2C Quick Reference (https://docs.pycom.io/wipy2/2wipy/quickref.html#i2c-bus) which is the same for both versions of Wipy.

Thanks a lot for your help!

Michal

[daniel]

Hi Michal,

Thanks for the quick feedback, glad that it works now :-)

I got confused with I2C Quick Reference (https://docs.pycom.io/wipy2/2wipy/quickref.html#i2c-bus) which is the same for both versions of Wipy.

It's our fault, we need to make the API accept an integer as well. Will be fixed shortly.

Cheers,
Daniel

[Baruch1966]

@michal said in Wipy 2.0 and BME280 sensor:

I can see the device on I2C bus, so the wiring should be OK. I also have a HD44780 display with PCF8574 backpack connected to I2C bus and it works.
I am using the latest firmware 0.9.4b1.

Can you share a example code with PCF8574?

[michal]

@Baruch1966
Hi!

Here is the repository with driver from Dave Hylands:
https://github.com/dhylands/python_lcd

Here is the sample code:

from machine import I2C
from i2c_lcd import I2cLcd

i2c = I2C(0, I2C.MASTER, baudrate=100000)
lcd = I2cLcd(i2c, 0x27, 4, 20)
lcd.putstr("It Works!")

I use this display: http://www.santy.cz/zobrazovace-c7/lcd-2004-blue-i2c-i9/
and this level converter: http://www.santy.cz/moduly-omezovacu-a-prevodniku-c34/i2c-uart-level-konvertor-3v-5v-4way-i223/

Michal

[Jiemde]

Hi michal,

Also try to use the bme280 sensor ( working with the wipy1 ok! ) but have the same errors with the wipy 2!
Had you resolve this ? If yes could you tell me how ?

Best regards

Jiemde

[microman7k]

@Jiemde

Hi, It works with my Wipy 2.0, i think the only change i made was:

def write8(self, register, value):
"""Write an 8-bit value to the specified register."""
value = value & 0xFF
self._i2c.writeto_mem(self._address, register, bytes([value]))