Possible to run K20 while TK1 is shutdown?


I’ve been trying to get some form of low power mode working on the TK1. I have noticed that LP0/LP1 testing is in the roadmap for the BSP, but I am looking for a workaround till that is ready. I was thinking if the TK1 could be completely shut down (or maybe just the core clock set to 0Hz) while the K20 is still running? The K20 could then reset the TK1 on detection of appropriate event using an external GPIO tied to to the module’s reset line.

Is this a possibility? I understand that this would require custom firmware for K20 and some kernel drivers for TK1, but from a hardware perspective, are the power buses or reset lines of the TK1 and the K20 coupled? Or can they be controlled independently?

There are 5 wake-up capable interrupt lines going from the K20 to the TK1 so in theory it should be possible to keep the TK1 in LP0/LP1 suspend while the K20 is operating regularly even being able to wake the TK1 up again. That said it is not possible to completely shut down the TK1 as it is really the TK1 that is in control of the power management and there is no way the K20 can power the TK1 on again (or even reset it) once it is shut down.

OK. I guess once the LP0/LP1 suspend modes are implemented then waking up from the K20 interrupt lines should be the right approach to do this. But I’m just searching for interim solutions/hacks.

If, currently, there was any way to keep the K20 running, with the TK1 shutdown (or in some really low power state), would the K20 be able to reset the entire Apalis module by pulling down RESET_MICO# through a GPIO. The wiring would have to be external. While it’s not a suspend, more like a shutdown and restart, that would work for our application.


You may find at least working LP1 suspend with a patch on our -next branch here.

Thank you! I tried it! It works! Cool!

Now trying to see if I can keep the K20 running and wake up the TK1 through the interrupt pins.

I see the git repo for the K20 source code, is there a document for how to compile the firmware?

Currently the best way to work with firmware is to install https://www.nxp.com/kds and import project into it.

Just wanted to come back and update.

I have a successful running system where the TK1 can go into LP1 and the K20 can wake it up.

Thanks for your help!

You are very welcome. Glad it is working for you now and thanks for letting us know.