# Zephyr Proof-of-Concept-Device Bringup

It may be useful to build a Zephyr OS-based EC for a device which
already has a CrOS EC device build, for the purposes of demonstrating
the feasibility of Zephyr OS.

This document is a work-in-progress list of tricks & tools that may be
useful to you.

## Initial Bringup

Initially, you'll want to get a basic UART functioning with nothing
but a shell and some basic console commands.

An example CL to do this for Lazor can be found
[here](https://crrev.com/c/2749765).

## Bringing up GPIOs

After you have UART functioning, GPIOs can be an easy target to start
unblocking further features.

We have a very ugly program to auto-generate the GPIO DTS based on
gpio.inc for the existing board.  You can find it at
`util/gpios_to_zephyr_dts.c`, and instructions are in the file on how
to compile and use it.  You may have to hand-modify the output.

The resultant CL for Lazor can be found [here](https://crrev.com/c/2749768).

## Bring up Host Commands

Set `CONFIG_PLATFORM_EC_HOSTCMD=y` and enable the appropriate
host-command interface for your platform (e.g., eSPI).

An example CL for Lazor can be found [here](https://crrev.com/c/2749428).

As long as you get this compiling that should be enough to move to the
next step.  Further testing of the host command layer will require
power sequencing up and going.

For further explanation, check [AP-EC communication](zephyr_ap_ec_comm.md) document.

## Enabling some simple GPIO-based buttons and switches

Next, you can:

* [Add the lid switch](https://crrev.com/c/2749768)
* [Add the power button](https://crrev.com/c/2749426)
* [Add AC presence detection](https://crrev.com/c/2749428)

## Power Sequencing

TODO(jrosenth): add steps on enabling power sequencing and expand this
document.