Micropython support

[geoffklee]

I've made a small adapter class so that this can be used with micropython:

https://github.com/gkluoe/bme680/blob/master/library/bme680/i2c.py

@Gadgetoid would you consider a pull request to add this functionality?

[Gadgetoid]

Nice work!

I would probably package this separately- as a general purpose way to adapt Python SMBus dependent libraries to MicroPython. While it's convenient, it has too much utility to be bundled with bme680.

Calling it something like micropython-smbus and having it supply an smbus importable module that you can use to shim up libraries that don't support supplying an alternate i2c object may be useful.

[geoffklee]

Thanks - that's a good idea. Of course, if I do that I'll have to stop being lazy and implement the rest of the smbus methods ;-) Hopefully it'll work for @robmarkcole in the meantime.

[robmarkcole]

@gkluoe Hi Geoff, thanks for posting. I have a pycom Wipy 2.0 and have flashed the code from your repo. Do you have an example main.py where you init the i2c object as they do in the pycom docs? Have tried:

>>> sensor = bme680.BME680(i2c_addr=i2c.scan()[0])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/flash/lib/bme680.py", line 22, in __init__
ImportError: no module named 'smbus'

Happy to move this discussion to your repo but can't see an option to create an issue there.
Finally it appears you intend to add this sensor to a weather-station which is my project too :)

[geoffklee]

Hi,

It's not quite a drop-in replacement for smbus (yet :) so you need to create an instance of the I2CAdapter and pass it to the BME680 constructor explicitly. OTOH, you probably don't need to set i2c_addr when you're initing the 680, unless you've changed it from the default, so this should work (I'm on a LoPy but I think the firmware is essentially the same):

from bme680.i2c import I2CAdapter

i2c_dev = I2CAdapter(1, I2C.MASTER, baudrate=100000)
bme680.BME680(i2c_device=i2c_dev) 

If you're not using the default pins, you can specify them explicitly:

i2c_dev = I2CAdapter(1, pins=('G15','G10'), baudrate=100000)
bme680.BME680(i2c_device=i2c_dev)

I've enabled issues on my fork now so if you're still having problems or have suggestions feel free to head over there! I'll tidy things up a bit and move the adapter into its own repo at some point soon.

[robmarkcole]

Thanks @gkluoe that solution works on my Wipy :-)

[Thosch42]

Hi!
I tried it also on a LoPy, but the line
i2c_dev = I2CAdapter(0, I2C.MASTER, baudrate=100000, pins=('P9', 'P10'))
give me an error: NameError: name 'I2C' is not defined.
Since I'm a 'C' guy, I'm pretty new in Python coding. As far as I understand, the I2C module is loaded, bacause I get no ImportError. But why is then I2C not defined?

Cheers,
Thomas

[geoffklee]

Hi - I2C isn't defined because you haven't imported it, you've imported I2CAdapter instead :-)

So, I suspect

i2c_dev = I2CAdapter(0, I2CAdapter.MASTER, baudrate=100000, pins=('P9', 'P10'))

Would work for you in this particular case.

Fwiw, I've done a bit of work to generalise this out - it's a bit of a mess to use it at the moment but the readme should get you there:

https://github.com/gkluoe/micropython-smbus

[Thosch42]

Arghh, your'e right!!
Have you recognized any memory problems with your LoPy? During the burn in, I get an MemoryError: memory allocation failed, allocating 1024 bytes.

[robmarkcole]

Btw am writing this up https://github.com/robmarkcole/bme680-mqtt-micropython

[geoffklee]

I get the same error – I think the burn-in script just uses up too much RAM to work on a LoPy (or is causing a lot of fragmentation somehow) IIRC there is ~79KB free RAM on a LoPy .. it’s probably optimisable somehow… You can use `gc.collect()` Followed by `gc.mem_free()` To see what’s going on… The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336.

[papics]

Hi guys,

I am trying to use the i2c and bme680 libraries, but I am having some difficulties. I have quite some experience in python, but this is the first time I am working with sensors and micropython, so maybe you can help (even though this is not an actual Issue in your code on github).

I have an Adafruit HUZZAH32 - ESP32 Feather Board to which I installed micropython (following https://www.rototron.info/raspberry-pi-esp32-micropython-tutorial/ and actually I already made this work with a DHT22 sensor on another ESP32, so I know that this part should be all right, and I have also made use of the MQTT protocol there before, so that part works too), to which I have wired a BME680 using the default scl/22 and sda/23 pins.

Using only

...
import bme680
from i2c import I2CAdapter
...

...
i2c_dev = I2CAdapter()
sensor = bme680.BME680(i2c_device=i2c_dev)
...

my code gives an error: "TypeError: 'scl' argument required" on line "i2c_dev = I2CAdapter()"

So I tried with my basic understanding getting to the bottom of this, and I can get to the next line in the code at least if I do:

i2c_dev = I2CAdapter(scl=machine.Pin(22),sda=machine.Pin(23))

which results in an error: "OSError: [Errno 19] ENODEV" on line "sensor = bme680.BME680(i2c_device=i2c_dev)"

One more thing I tried is to see if this setting sees the connected sensor, by

i2c_dev.scan()
[119]

So I think that should be fine, but I have no idea how to progress from here...
I had no issues make this setup work with the DHT22 sensor, but I am pretty stuck with the BME680. I would appreciate any kind of suggestions about what I am doing wrong.

Best regards,
Peter

[geoffklee]

Hi. Interesting.

If scan() is working, then I'm not sure where to go with this one.

I hacked together the I2CAdapter for a LoPy and that's all I have tested it on. We have reports of it working on a WiPy too, but it's possible the generic ESP32 micropython is sufficiently different that it's doing something I didn't anticipate.

Are you able to get any more of a traceback?

You could also try the more generic version of the adapter - it might be a bit more clear what it's doing: https://github.com/gkluoe/micropython-smbus