Not working with I2C on MCP2221

[caternuson]

Re this thread:
https://forums.adafruit.com/viewtopic.php?f=19&t=181641

Tried various slower bus speeds and still no success.

[truher]

this combination doesn't work for me either.

[dhalbert]

The BNO085 is flaky enough that I'm not surprised: https://learn.adafruit.com/i2c-addresses/troublesome-chips

[truher]

i'm curious if anyone has had success with the UART mode between these two modules?

[bhupiister]

I am testing the same right now and even i get this error. @ladyada Any thoughts on this?

[ladyada]

BNO085 I2C is kinda a mess, i'd try the RVC UART mode

[jknecht-chromo]

Has anyone found any work arounds for this?
using the MCP2221A with the bno085?
I was working with the board, and recently I started encountering these i2c errors

[dhalbert]

You could try the stronger pullup on SDA trick mentioned here: https://forums.adafruit.com/viewtopic.php?t=183941, but it may not help. Let us know if it does. As mentioned, the chip violates various I2C protocol rules. You could try the UART RVC mode, as suggested, or connect the chip to a microcontroller that does work with it and communicate with the microcontroller over serial

[jknecht-chromo]

@dhalbert, thanks for the tip — I’ll give the stronger SDA pull-up trick a try and report back if it moves the needle.

I’m also eyeing the Adafruit breakout (product 4970) to see if it sidesteps the MCP2221A’s I²C quirks — have you ever used that board? Ideally I’d like to stick with a USB interface, but if it keeps misbehaving I’ll fall back to slinging it through a microcontroller over serial. Any experience or thoughts on the breakout would be super helpful!

[dhalbert]

I don't have an I2CMini to try. I should get one. You could ask support@i2cdriver.com. I don't see any mention of BNO085 in the GitHub repo for the I2CDriver.

The BNO085 does have a direct UART interface, so you could try that with a USB-serial converter.