Add custom README instructions for building custom firmware

Author: arcanemachine

README.md

@@ -1,13 +1,36 @@
-# Zephyr™ Mechanical Keyboard (ZMK) Firmware
+# ZMK (For Use With the Ergo S-1 Keyboard)
 
-[![Discord](https://img.shields.io/discord/719497620560543766)](https://zmk.dev/community/discord/invite)
-[![Build](https://github.com/zmkfirmware/zmk/workflows/Build/badge.svg)](https://github.com/zmkfirmware/zmk/actions)
-[![Contributor Covenant](https://img.shields.io/badge/Contributor%20Covenant-v2.0%20adopted-ff69b4.svg)](CODE_OF_CONDUCT.md)
+This repo is a fork of [ZMK](https://github.com/zmkfirmware/zmk) that allows you to build custom firmware for your Ergo S-1 keyboard.
 
-[ZMK Firmware](https://zmk.dev/) is an open source ([MIT](LICENSE)) keyboard firmware built on the [Zephyr™ Project](https://www.zephyrproject.org/) Real Time Operating System (RTOS). ZMK's goal is to provide a modern, wireless, and powerful firmware free of licensing issues.
+> NOTE: This repo is intended to provide customization for the [Ergo S-1](https://github.com/wizarddata/Ergo-S-1) keyboard only. These instructions will probably not work with any other custom keyboards.
 
-Check out the website to learn more: https://zmk.dev/.
+To create a custom layout and build your own firmware:
 
-You can also come join our [ZMK Discord Server](https://zmk.dev/community/discord/invite).
+  - First, follow the instructions in [my other GitHub repo](https://github.com/arcanemachine/ergo-s-1-zmk-config) to create a custom keymap file. (The file will be located at `config/ergo_s1_oe.keymap` in the other repo.)
+    - You can also just copy the keymap directly from the Keymap Editor web application and paste its contents to the correct path in this repo (described in the next steps).
+  - Once you have created a keymap, clone this repo (the one you are currently reading) so you can set up a ZMK development environment and build a custom firmware using your new keymap.
+  - Copy your new keymap file to the correct location in this repo (the one you are currently reading): `app/boards/shields/ergo_s1_oe/ergo_s1_oe.keymap`
+  - Set up your ZMK development environment (NOTE: The native version did not work for me, but the Dockerized version (using Devcontainers CLI) did work): [Link to docs](https://zmk.dev/docs/development/local-toolchain/setup/container?container=cli), [Archived link to docs](https://archive.is/hkw83)
 
-To review features, check out the [feature overview](https://zmk.dev/docs/). ZMK is under active development, and new features are listed with the [enhancement label](https://github.com/zmkfirmware/zmk/issues?q=is%3Aissue+is%3Aopen+label%3Aenhancement) in GitHub. Please feel free to add 👍 to the issue description of any requests to upvote the feature.
+> NOTE: If you install the Dockerized version, ensure that you are running the following commands from the Devcontainers CLI terminal that is running inside the container.
+
+  - Once you have installed your ZMK development environment, run the following commands to build the custom firmware for each side of the keyboard:
+    - Navigate to the `app` directory: `cd app`
+    - Build the firmware for the left side: `west build -d build/left -p -b nice_nano -- -DSHIELD=ergo_s1_oe_left`
+    - Build the firmware for the right side: `west build -d build/right -p -b nice_nano -- -DSHIELD=ergo_s1_oe_right`
+    - (If using Docker) Move the files to a path that is outside the Docker volume:
+      - `mv build/left/zephyr/zmk.uf2 ../ergo_s1_oe_left.uf2`
+      - `mv build/right/zephyr/zmk.uf2 ../ergo_s1_oe_right.uf2`
+  - Now that you have the firmware files, you can flash them to the keyboard. Perform the following instructions for each side of the keyboard:
+    - Double-press the reset button on the back of the keyboard to enter the bootloader mode.
+    - Plug in a USB cable to the keyboard so you can flash the firmware file.
+    - The keyboard will appear as a mounted drive in your file explorer.
+    - Copy the firmware file for the correct side to this mounted drive.
+    - After the file is copied, the keyboard will automatically reset itself, and will be working with the new firmware.
+    - Now, repeat these steps to flash the correct firmware for the other side of the keyboard.
+
+Congratulations! You have finished flashing your custom keymap to your Ergo S-1 keyboard!
+
+---
+
+Special thanks to the creator of the Ergo S-1 keyboard!