I2C not working correctly

[bill-orange]

I am using the Arduino 1.8.9 IDE on a ATTiny85 clone with a BME380. 10K pullups are on the I2C lines. An external battery assures that 5v is adequate.

I can compile properly. I can serial print to NotePad using keyboard.h. I can blink LEDs successfully.

What I can not do is successfully implement I2C. I do not know how to troubleshoot the problem.

If I use I2C scanner, the device is detected but I get back address 0x40 for a BME280. Clearly this is wrong. The address is 0x76.

If I try reading the BME280 (at any address), I get decimal 12378. Something is definitely wrong. I am very familiar with the ESP8266 family but I am too new with this device to work toward a solution by myself.

[technoblogy]

Are you using the Arduino IDE? If so, which ATtiny85 core are you using?

You say it's an ATtiny85 clone. Which one exactly?

[bill-orange]

I am using Digispark (default) on this board (more or less, the resistor arrangement is slightly different):

[technoblogy]

I'm not sure the Digispark supports I2C - search the web for information. I recommend using Spence Konde's ATTinyCore which does support I2C.

[bill-orange]

That could be the problem. I have certainly tried everything I can think of. Their drawing shows I2C connections but I don't think that is a reliable indicator.

[technoblogy]

Why don’t you try an ATtiny85 on a breadboard? David

[aholz]

You have not disclosed your code. Maybe you did not included <Wire.h> before <TinyBME280.h>?
Because on the ATTiny, I2C is implemented in software. But it works, I am running with BME280.

[nhabongo]

Hi, I am also trying to use the TinyBME280 lib with a Digispark attiny85 board. It gives me accurate measurements for temperature and humidity but returns a very low value for pressure. Using Adafruit_BME280 lib on an arduino uno i get a value of 92239 while digispark give me 26797. Any ideas ?

[technoblogy]

The Digispark causes a lot of compatibility problems. Try a standard ATtiny85.

[nhabongo]

Unfortunately that is true. I am giving up on digispark. Thanks for your reply.