zephyr-isr

zephyr-isr is a skill for Claude Code, Codex from ksachdeva/zephyr-rtos-ai. It costs 71 tokens per session (1,141 once invoked), scanned A, original, Apache-2.0.

A guide to interrupt service routines (ISRs) in Zephyr, which are short handlers that run when hardware raises an interrupt.

In plain words
What is it for?
Use it to configure regular, dynamic, direct, shared, or low-latency interrupts, manage priorities, and move longer work from an ISR to a thread or work queue.
Why use it?
Interrupt handlers have strict limits: they must not block, and many kernel operations are unsafe there. The guide helps keep interrupt work safe and responsive.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to configure regular, dynamic, direct, shared, or low-latency interrupts, manage priorities, and move longer work from an ISR to a thread or work queue.

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Install with agentmods
npx agentmods add skills/ksachdeva/zephyr-rtos-ai/zephyr-isr
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add ksachdeva/zephyr-rtos-ai --skill zephyr-isr
Clone the repo
git clone --depth 1 https://github.com/ksachdeva/zephyr-rtos-ai

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for zephyr-isr

README.md
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Your own site
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Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for zephyr-isr

Your own site · 80×15
<a href="https://agentmods.dev/skills/ksachdeva/zephyr-rtos-ai/zephyr-isr"><img src="https://agentmods.dev/badge/skills/ksachdeva/zephyr-rtos-ai/zephyr-isr.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 71 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,141 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00071 $0.01141
Opus 5 $0.00036 $0.00571
Sonnet 5 $0.00014 $0.00228
Haiku 4.5 $0.00007 $0.00114

Measured 12d ago against content hash 0d988b13848b, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

zephyr-isr scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 12d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/zephyr-isr/SKILL.md · 136 lines

How it starts

The opening of the file, as written. The whole thing — 136 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Zephyr ISR (Interrupt Service Routines)

Overview

This skill provides expert knowledge on interrupt handling in Zephyr RTOS. It covers ISR registration (static and dynamic), direct ISRs for low-latency handling, IRQ management, interrupt context constraints, and patterns for offloading work from ISRs to threads.

Key Constraints (Memorize)

ISR Context Rules:

  • ISRs run on a dedicated interrupt stack
  • ISRs can be nested (higher priority preempts lower)
  • ISRs must never block - no K_FOREVER or K_MSEC(n) timeouts
  • Use k_is_in_isr() to detect interrupt context
  • Many kernel APIs are thread-only; check docs before use in ISR

ISR-Safe Operations:

  • k_sem_give() - always safe
  • k_sem_take(&sem, K_NO_WAIT) - safe (non-blocking)
  • k_msgq_put() / k_fifo_put() with K_NO_WAIT - safe
  • k_work_submit() - safe (offload to system workqueue)

Workflow

1. Choose ISR Type

Type Use When Registration
Regular Most cases, arguments known at build time IRQ_CONNECT()
Dynamic Arguments known only at runtime irq_connect_dynamic()
Direct Ultra-low latency required IRQ_DIRECT_CONNECT()

Step 1: Read references/isr-types.md for detailed implementation of each type.

2. Implement ISR

Once the ISR type is chosen, implement the handler:

/* Regular ISR */
void my_isr(const void *arg)
{
    /* Fast processing only - never block */
}

/* Direct ISR (for lowest latency) */
ISR_DIRECT_DECLARE(my_direct_isr)
{
    do_minimal_work();
    ISR_DIRECT_PM();  /* Power management hook */
    return 1;         /* 1 = check reschedule, 0 = skip */
}

3. Register and Enable

/* Build-time registration */
IRQ_CONNECT(IRQ_NUM, PRIORITY, my_isr, my_arg, FLAGS);
irq_enable(IRQ_NUM);

/* Runtime registration */
irq_connect_dynamic(IRQ_NUM, PRIORITY, my_isr, my_arg, FLAGS);
irq_enable(IRQ_NUM);

4. Offload Time-Consuming Work

Read the full file on GitHub · 136 lines

Files

What ships with it

4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 12d ago First seen · 136 lines · 71 tokens per session scan A 0d988b13848b

Subscribe to this mod's changes

zephyr-isr is a skill published in the GitHub repository ksachdeva/zephyr-rtos-ai (23 stars, last pushed 3mo ago), licensed Apache-2.0. It adds 71 tokens to every session and 1,141 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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