Hands-On: Build a Custom Zephyr BSP in 90 Minutes with AI

diff --git a/.claude/skills/kconfig-tuner/SKILL.md b/.claude/skills/kconfig-tuner/SKILL.md
index 02cd76f..5b5df17 100644
--- a/.claude/skills/kconfig-tuner/SKILL.md
+++ b/.claude/skills/kconfig-tuner/SKILL.md
@@ -23,12 +23,18 @@ Translates plain-English Zephyr feature requests into a minimal, verified set of

+Mandatory Gate: If target_file is omitted and the user did NOT explicitly request "dry-run" or "dry run", the agent MUST STOP immediately and ask the user for target_file. The repository contains multiple lab projects; the agent must never guess or silently default to dry-run mode.
+

Procedure

+0. Check required inputs (Input Gate):

• • If dry_run is true (the user explicitly requested dry-run mode in their prompt, e.g. "dry run" or "dry-run"): proceed to Step 1.
• • If target_file was NOT specified: STOP IMMEDIATELY. Do not run grep checks, do not generate diffs or the output report. Ask the user: "Which target file (for example, Labs/Labs/Lab3/Starter/app/prj.conf) should be updated? This repository contains multiple projects."
• • If target_file was specified: verify test -f <target_file> before editing.
    1. Parse the goal into 1 or more candidate Kconfig symbols.
  • "shell over UART" -> CONFIG_SHELL, CONFIG_SHELL_BACKEND_SERIAL, CONFIG_SERIAL, CONFIG_UART_CONSOLE
  • "logging" -> CONFIG_LOG
    @@ -41,16 +47,18 @@ Translates plain-English Zephyr feature requests into a minimal, verified set of

    
    If grep returns no result, the symbol does not exist. **Refuse to include unverified symbols. Never fabricate.**
    3. **Construct the minimal diff.** Drop any symbol whose default is already `y` for the target board (use the reference `_defconfig` to check). Keep only what the user must add.
    -4. **Optionally write to `target_file`.** If `dry_run` is true, just report.
    +4. **Apply diff or report.**

• • If dry_run is true: report the verified diff without modifying files.
• • If target_file is provided: write/append the verified symbols to target_file.

  Self-Validation Protocol

  #	Check	How to verify
  +	---	---	---
  1	Goal was parsed into >=1 candidate	the diagnosis lists at least one CONFIG_ symbol
  2	Every proposed CONFIG_ symbol exists in the Zephyr tree	for each symbol, grep -rl "^config <SYMBOL>$" /workdir/zephyr /workdir/modules returns at least one path; the path is reported
  3	No fabricated symbols	the count of (proposed) == count of (verified)
  -	4	Target file exists if write was requested	test -f <target_file> before edit
  +	4	Target file handling	if write requested, test -f <target_file>; if omitted without dry-run, stop and prompt user for path
  5	Diff is minimal (no symbols already implied by board defconfig)	manual cross-check; report which were dropped

  If check 2 or 3 fails: the offending symbol must NOT be reported. Report only the verified subset, plus a note about the unverified ones with the suggestion to ask the user for guidance.
  @@ -61,7 +69,7 @@ No retries on symbol verification -- a missing symbol means the candidate was wr

  Output format

-The agent MUST wrap the output in a fenced code block (text ...) so that monospace alignment and line breaks are preserved in Markdown:
+When target_file is provided or dry-run is explicitly requested, the agent MUST wrap the output in a fenced code block (text ...) so that monospace alignment and line breaks are preserved in Markdown:

 kconfig-tuner result: PASS  (or FAIL)
@@ -80,21 +88,28 @@ Validation:
   [x] candidates parsed:    4 symbols
   [x] every symbol verified in Zephyr tree
   [x] no fabricated symbols
-  [-] target_file exists:   (dry-run, no file requested)
+  [x] target_file exists:   Labs/Labs/Lab2/Starter/app/prj.conf  (or: [-] dry-run requested)
   [x] minimal diff:         no symbols dropped as already-default

Examples

-### Example 1: enable shell over UART
+### Example 1: target_file omitted without dry-run
+
+User: "/kconfig-tuner enable logging with UART backend in immediate mode"
+
+Output: Agent stops immediately and asks:
+"Which target file (e.g. Labs/Labs/Lab2/Starter/app/prj.conf or boards/nxp/frdm_mcxa156_workshop/frdm_mcxa156_workshop_defconfig) should be updated? This repository contains multiple projects."
+
+### Example 2: explicit dry-run mode

-User: "what do I need in prj.conf to get a shell prompt over the console?"
+User: "Use the kconfig-tuner skill (dry-run mode) to determine the minimum verified CONFIG_* set for this goal: enable shell over UART"

-Output: 4 symbols (SHELL, SHELL_BACKEND_SERIAL, SERIAL, UART_CONSOLE), each verified.
+Output: 4 symbols (SHELL, SHELL_BACKEND_SERIAL, SERIAL, UART_CONSOLE), each verified, marked with [-] target_file exists: (dry-run mode requested).

-### Example 2: refuse unverified
+### Example 3: refuse unverified

-User: "enable CONFIG_FANCY_FEATURE"
+User: "enable CONFIG_FANCY_FEATURE in Labs/Labs/Lab2/Starter/app/prj.conf"

Output: kconfig-tuner refuses. Symbol not found in Zephyr tree (verified via grep). Suggest the user check the spelling or find the closest matching real symbol.

diff --git a/CLAUDE.md b/CLAUDE.md
index c869456..e2234ae 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -96,7 +96,7 @@ beningo_eoc26_zephyrAI/

8. Prefer mirroring frdm_mcxa156_reference/ over generating from scratch. When a structural decision exists in the reference BSP, mirror it.
9. Never claim a build succeeded without showing the exit code. west build errors must be captured by the build-doctor skill, not paraphrased.

10. Never assume west flash or west debug works in-container on macOS or Windows. USB passthrough is not supported. Flash from the host with VS Code F5 (Cortex Debug + LinkServer) or LinkServer flash MCXA156:FRDM-MCXA156 load build/zephyr/zephyr.elf.
    -11. Skills do not offer pedagogical choices. When invoked as a skill (build-doctor, devicetree-author, kconfig-tuner, zephyr-bsp-scaffold, renode-runner), produce the diagnosis or artifact, run the Self-Validation Protocol, and stop. Do not ask the attendee how they want to teach the topic, whether to apply the fix, or whether this is a teaching moment. The attendee decides next steps in their own prompt. Workshop framing belongs in CLAUDE.md, not in skill output.
    +11. Skills do not offer pedagogical choices. When invoked as a skill (build-doctor, devicetree-author, kconfig-tuner, zephyr-bsp-scaffold, renode-runner), produce the diagnosis or artifact, run the Self-Validation Protocol, and stop. Do not ask the attendee how they want to teach the topic, whether to apply the fix, or whether this is a teaching moment. The attendee decides next steps in their own prompt. Workshop framing belongs in CLAUDE.md, not in skill output. Exception: if a required input (such as target_file) is missing and no dry-run flag was set, stop immediately and ask the user for the required input.

    Hardware Target

@@ -109,7 +109,7 @@ beningo_eoc26_zephyrAI/

The Practical Zephyr BSP Model

-A Zephyr board is a small system of files, each responsible for one layer of configuration. There is no canonical "N-file model" — boards vary, and structures shift across versions and vendors. What matters is the layering. Understanding the split is what makes Zephyr portable.
+A Zephyr board is a small system of files, each responsible for one layer of configuration. There is no canonical "N-file model" - boards vary, and structures shift across versions and vendors. What matters is the layering. Understanding the split is what makes Zephyr portable.

At a minimum, most boards rely on:

Interesting. If you haven't gotten it to work yet, give this command a try:

docker compose -f docker/docker-compose.yml build --build-arg TARGETARCH=amd64

Thank you.

I don't see why not. You can use the Ollama API's to have claude call into it. I've not tried it myself though.

No, I haven't verified it. I use MacOS. You should be able to take the generation process though and get it running on your machine.

We had several Linux folks during the live session who had it running.

hint: Use AI to help you through the set up

Thanks!

Thank you.

THere is a conference attendee forum you can also use, but yes you can ask questions here.

Thanks!

Thanks for letting me know!