I have tried with both a GY-302 and a GY-30 and both don't work although they show different problems (mentioned on my OP). Both the sensors work well when connected to the pi.

I don't have a drawing of the circuit but I can show you a picture, if it helps.

The diagram is essential like this one but without the temperature sensor and I am currently using an FTDI board to provide the power, instead of a battery.

The SCL is connected to A5 and the SDA to A4 of the mini pro.

I can also do a drawing, if further info is required but, as I said, it is like the one I linked above.

@alexsh1 Very true Anyways, thanks for the tips!

@alexsh1 I just realized my full blown stupidity. The breadboard I am using has the buses connected half way and I was convinced they were fully connected. So the light sensor was not getting power, obviously.

It works now.

@alexsh1 Thanks I will check it out and give it a try! I'll let you know the results

@alexsh1 I think I will try to get a more reliable FTDI since this one seems to give me some troubles. It also isn't properly detected on my PC sometimes. Is there a reliable one I could get from, for example, aliexpress, you recommend? My knowledge on these is close to zero, hahaha. Thanks.

@alexsh1 Hm that seems reasonable. The FTDI board I have seems to be a bit funky it gives a lot of errors when I am trying to upload sometimes. Could that be related? I am not sure if it is the FTDI or the mini pro itself though.

I don't have another type with me though.

@alexsh1 I ran this example: https://playground.arduino.cc/Main/I2cScanner (I'm not sure if this is what you meant).

It seems to hang on Wire.endTransmition() it prints the string "Scanning..." but nothing else.

@alexsh1 There doesn't seem to be no RF issues, no. The freezing occurs on Wire.endTransmition(), not begin. I meant the begin function of the BH1750 library from MySensors, sorry if that wasn't very clear.

SDA and SDL seem to be connected correcly. I've checked that a few times now.

Not at the moment but I ordered a DHT22 sensor I can try that when it arrives.

I have tried with both a GY-302 and a GY-30 and both don't work although they show different problems (mentioned on my OP). Both the sensors work well when connected to the pi.

I don't have a drawing of the circuit but I can show you a picture, if it helps.

The diagram is essential like this one but without the temperature sensor and I am currently using an FTDI board to provide the power, instead of a battery.

The SCL is connected to A5 and the SDA to A4 of the mini pro.

I can also do a drawing, if further info is required but, as I said, it is like the one I linked above.

@alexsh1 said in BH1750 library hangs:

ESP8266

You mean a different model? Unfortunately I don't have another model to test it, only mini pro. I have tried another mini pro (same manufacturer though). I also don't have another model of the radio. But the messages are being sent properly so I am not sure if the problem could come from that.