Compatibility issues of the Digi2 Pro and Raspberry Pi 4 Rev. 1.5

We have received reports from some users that the Digi2 Pro was not detected by the Pi4. We couldn’t see this issue with our boards. It also never showed during manufacturing tests. As we saw more of these problems in the last week, we finally got a Pi and Digi2 combination from an affected user.

The good news: We could reproduce the problem and identify the root cause. The bad news: It seems there is no simply software-based fix. The new Pi release uses a new power management circuit that doesn’t ramp up the voltages as clean as all previous versions did.

Previous versions:

The new hardware release:

As you can see the startup isn’t as clean as it was on previous releases. This results in an inconsistent state of the circuit and the Digi2 Pro isn’t detected by the Pi anymore.

Note that this affects only the Digi+ Pro and Digi2 Pro.

Next steps

We’re waiting for feedback from the Raspberry Pi foundation if this is an normal behavior or if there is a hardware problem. Based on the feedback we will plan the next steps.

February 15, 2022

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