# Kernel Basics

> Essential Zephyr RTOS kernel services. Covers thread lifecycle and priority, the logging subsystem for diagnostics, and the interactive shell for real-time hardware inspection and debugging. Trigger when writing application flows, adding logging to modules, or creating interactive CLI commands. Use when this capability is needed.

- Skill: `tomevault-io/kernel-basics` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/kernel-basics`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/kernel-basics/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: AI & ML
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/kernel-basics

---


# Zephyr Kernel Basics

Master the essential services that bring your Zephyr application to life.

## Core Workflows

### 1. Threads & Scheduling
Create and manage multi-threaded application flows.
- **Reference**: **[threads.md](references/threads.md)**
- **Key Tools**: `K_THREAD_DEFINE`, `k_sleep`, `k_yield`, Priorities.

### 2. Logging & Diagnostics
Implement layered logging for better observability and troubleshooting.
- **Reference**: **[logging.md](references/logging.md)**
- **Key Tools**: `LOG_MODULE_REGISTER`, `LOG_INF`, `LOG_ERR`, Dynamic Filtering.

### 3. Interactive Shell (CLI)
Build powerful command-line interfaces for hardware and software inspection.
- **Reference**: **[shell.md](references/shell.md)**
- **Key Tools**: `SHELL_CMD_REGISTER`, `SHELL_STATIC_SUBCMD_SET_CREATE`.

## Quick Start (Logging)
```c
#include <zephyr/logging/log.h>
LOG_MODULE_REGISTER(my_app, CONFIG_APP_LOG_LEVEL);

void my_fn(void) {
    LOG_INF("Hello from Zephyr!");
}
```

## Quick Start (Threads)
```c
K_THREAD_DEFINE(worker_tid, 1024, worker_fn, NULL, NULL, NULL, 5, 0, 0);
```

## Automation Tools
- **[log_summary.py](scripts/log_summary.py)**: Parse Zephyr runtime logs and summarize counts by level/module.

## Examples & Templates
- **[shell_command_template.c](assets/shell_command_template.c)**: Starter command set for shell registration patterns.

## Validation Checklist
- [ ] Log output includes module tag and expected log level filtering.
- [ ] At least one worker thread starts and runs at the intended priority.
- [ ] Shell command registration appears in `help` output and executes without faults.
- [ ] No blocking or mutex misuse appears in ISR-context paths.

## Resources

- **[References](references/)**:
  - `threads.md`: Configuration and creation of kernel threads.
  - `logging.md`: Log levels, modules, and backends.
  - `shell.md`: Interactive command registration and subcommands.
- **[Scripts](scripts/)**:
  - `log_summary.py`: Runtime log summarizer for quick diagnostics.
- **[Assets](assets/)**:
  - `shell_command_template.c`: Shell command registration template.

---
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<!-- tomevault:4.0:skill_md:2026-04-13 -->