Sharing I2C block between cores

Prerequisites

Please check the following before posting an issue / bug report.

• I am running the latest version of the firmware found HERE
• I have checked the documentation HERE and found no answer
• I checked to make sure that this issue has not already been filed HERE
• I am reporting the issue to the correct repository

Context

When writing a GP2040 addon for one of my own I2C input peripheral, I noticed that my peripheral would constantly glitch out. A protocol capture shows that the data exchange between RP2040 and both the OLED display and the peripheral are interleaved and corrupted.

This kind of setup is also allowed in some of the official addons like ADS1219 without (IIRC) explicit warning in the documentation so I'd presume that they would be supported, but broken as well.

• Firmware Version: 7aa176e
• Name of device: Any
• Link to where you purchased the device: Any
• Is this a custom build?: Yes
• Operating System: Any
• Browser: Any

Expected Behavior

I2C block is properly shared without corrupting the data.

Current Behavior

Data corruption occurs when the same block is used by 2 cores.

Steps to Reproduce

1. Enable OLED display
2. Enable some other addon that uses I2C and select the same block and pins the OLED display uses
3. Connect all devices to a single bus
4. Watch it crash and burn

Screenshots & Files

Please include any relevant screenshots or files here. If you are having issues with a board please include images of the front and back of the board.

Start by tracing how the OLED display and other addons access the shared I2C block and how those accesses are assigned across the two cores. Reproduce the issue using the listed OLED-plus-addon setup and a shared bus; done means both devices exchange data without corruption or crashes.