Power sequencing and driver intialisation

Glenn Andrews

Hi All,

We're building a custom board with a no-standard power sequence.

The processor and a TCA6418 GPIO expander come up first on a low-current 1V8 supply. The TCA6418 controls the enable pins for all the power regulators in the system, including the high-current 1V8 that powers the rest of the devices connected to the processor.

So order of initialization will be:
  1. A single I2C bus
  2. TCA6418
  3. Enable other regulators and wait a bit
  4. All other external devices, including other devices on the I2C bus.

Is it possible to do this using just the priority levels in the drivers?

For legacy reasons we're using Zephyr v2.3.0 and are unlikely to be able to upgrade to a newer version any time soon.



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