Issue connecting ESP8266 Thing to BNO080

[eskhisov]

I am trying to connect ESP8266 Thing, or any ESP8266 board for that matter, to BNO080 via I2C interface and it is not working.
I have tried different things, including setting different parameters on Wire library, but nothing works. Even when ESP8266 recognizes that there is a sensor attached, which seems to be about 70% of the time, the loop() function does not generate any data. If I turn on debugging, I get a steady stream of 'I2C Timeout' messages.

[eskhisov]

Ok, so I've got it to work, sort off. See attached code, which is modified Example1-RotationVector.ino.
Caveats:

1. ESP8266 Thing does work when I load the code for the first time. Then, when I switch off and on, it mostly does not work, but does work sometimes.
2. I also tried it with generic ESP8266, which is this one https://www.amazon.com/gp/product/B010N1SPRK
   With this one, it works almost always. It does have reset button instead of on/off switch, but it failed maybe once out of 100 resets.

sketch_nov23a.ino.txt

[nseidle]

ESPs are notorious for their odd I2C issues. I can't work on this at the moment but we've found various solutions

• Add a bit of time at beginning of the sketch before the myIMU.begin() to allow the BNO080 to boot
• Increaset the Wire.setTimeouts() before the myIMY.begin() to allow the BNO080 to clock stretch when needed

[eskhisov]

I will try those suggestions.

[DaStewie]

Having the following in the setup got it working for me, don't ask me why.
Connection:
SDA = 4 => D2.
SCL = 5 => D1

Setup:

delay(100); // Allow BNO080 to startup

// Start i2c and BNO080
Wire.begin(5, 4); // idk why but removing this wouldnt work
IMU.begin(BNO080_DEFAULT_ADDRESS, Wire);
Wire.begin(4, 5); //
Wire.setClockStretchLimit(4000);

[eskhisov]

@DaStewie Wow, it does work. My setup is 2,14 but it works for it too:

delay(100); //would not work without this delay
Serial.println("BNO080 Read Example");

Wire.begin(5,4);
myIMU.begin(BNO080_DEFAULT_ADDRESS, Wire);
Wire.begin(2, 14); // (SCLpin,SDApin)
Wire.setClockStretchLimit(4000);

[DaStewie]

Managed to figure out what Wire.begin(5, 4) did. Using flush resets the index and allows for a proper startup.

  delay(100); //  Wait for BNO to boot

  // Start i2c and BNO080
  Wire.flush();   // Reset I2C
  IMU.begin(BNO080_DEFAULT_ADDRESS, Wire);
  Wire.begin(4, 5); 
  Wire.setClockStretchLimit(4000);

[eskhisov]

This works too. And much more rational.

[nseidle]

Thanks you two! I've added this code (commented out) and a link to this issue in Example 1. Hopefully it will help future ESP users.