Apalis T30 GPIO Power Up


I’ve configured some GPIO pins in u-boot as digital outputs with their initial state set as low.

For a very short period, when power is first applied to the Apalis T30 module these GPIO pins are drive high before u-boot kicks in and sets them to their correct state.

Is there any way I can prevent these signals from driving high for this initial period? Is there any lower level function where the GPIO configuration could sit preventing this behaviour?

Kind regards,

The only reliable way to get this working across all different Apalis modules is using an external buffer on any such GPIO being gated by the POWER_ENABLE_MOCI# signal.

Hi Marcel,

I’m not bothered about it running across all different Apalis modules, just the ones we’re using.

Is there anywhere lower in the code (like at the start up of the core) where I can set some basic initial GPIO states? Surely this must be a possibility?

Kind regards,

No, unfortunately there isn’t. U-Boot is the first code running which one can have any direct influence on and configure such things as e.g. pin muxing.

However if you limit yourself to just one module type you may get around it by carefully studying the I/O pin function list (Apalis T30 datasheet section 4.4) and choosing pins according to your desired reset state. Careful though as this may be subject to change and is definitely not guaranteed across various module types.