i2c-bringup-diagnostician

i2c-bringup-diagnostician is a skill for Claude Code from wedsamuel1230/arduino-skills. It costs 64 tokens per session (729 once invoked), scanned A, original, MIT.

A step-by-step guide for finding faults in I2C, a short-distance communication bus commonly used by sensors and displays, on Arduino and ESP32-class boards. It covers wiring, addresses, pull-up resistors, bus settings, and board-specific behavior.

In plain words
What is it for?
Use it when no devices are detected, a scanner finds a device but its library cannot start it, two devices share an address, or readings are wrong because of pins, pull-ups, wiring, or voltage levels.
Why use it?
An I2C scanner finding a device does not prove that the wiring, voltage, pins, or library setup is correct. The guide narrows down why devices are missing, conflicting, unreadable, or only partly working.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the arduino-skills plugin — 33 skills shipped together

Good fit Use it when no devices are detected, a scanner finds a device but its library cannot start it, two devices share an address, or readings are wrong because of pins, pull-ups, wiring, or voltage levels.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/wedsamuel1230/arduino-skills/i2c-bringup-diagnostician
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 wedsamuel1230/arduino-skills --skill i2c-bringup-diagnostician
Clone the repo
git clone --depth 1 https://github.com/wedsamuel1230/arduino-skills

Made for: Claude Code.

Or install arduino-skills, the plugin that ships this one along with the rest of its 33 skills.

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 i2c-bringup-diagnostician

README.md
[![agentmods](https://agentmods.dev/badge/skills/wedsamuel1230/arduino-skills/i2c-bringup-diagnostician/github.svg)](https://agentmods.dev/skills/wedsamuel1230/arduino-skills/i2c-bringup-diagnostician)
Your own site
<a href="https://agentmods.dev/skills/wedsamuel1230/arduino-skills/i2c-bringup-diagnostician"><img src="https://agentmods.dev/badge/skills/wedsamuel1230/arduino-skills/i2c-bringup-diagnostician/github.svg" alt="Measured on agentmods" height="20"></a>

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 i2c-bringup-diagnostician

Your own site · 80×15
<a href="https://agentmods.dev/skills/wedsamuel1230/arduino-skills/i2c-bringup-diagnostician"><img src="https://agentmods.dev/badge/skills/wedsamuel1230/arduino-skills/i2c-bringup-diagnostician.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 64 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 729 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 $0.00064 $0.00729
Opus 5 $0.00032 $0.00365
Sonnet 5 $0.00013 $0.00146
Haiku 4.5 $0.00006 $0.00073

Measured 12d ago against content hash b06951c7b3a3, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

i2c-bringup-diagnostician 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/i2c-bringup-diagnostician/SKILL.md · 79 lines

How it starts

The opening of the file, as written. The whole thing — 79 lines — stays where its author put it; the contents beside it link to each section on GitHub.

I2C Bringup Diagnostician

Use this skill when the sensor or device should be on the bus, but the I2C path is still not trustworthy.

Resources

  • references/bringup-flow.md - ordered I2C fault-isolation workflow
  • references/scanner-vs-library.md - what to do when the scanner finds the device but the library still fails
  • references/esp32-and-board-quirks.md - ESP32-family and board-specific caveats
  • ../../docs/board-support/uno-r4-family.md - Uno R4 family board notes when relevant

When to Use

Use this skill when the request includes:

  • "no I2C devices found"
  • scanner finds the address but the library cannot initialize the device
  • two I2C devices conflict or one disappears
  • ESP32 pin, bus, or second-channel confusion
  • pull-up, wire-length, or voltage-level questions
  • obviously wrong sensor values after basic detection succeeds

Workflow

  1. Establish the basic failure shape:
    • no scanner detection -> open references/bringup-flow.md
    • scanner detects but library fails -> open references/scanner-vs-library.md
    • ESP32-family multi-bus or pin issue -> open references/esp32-and-board-quirks.md
  2. Confirm the electrical basics before library swapping:
    • power
    • common ground
    • SDA and SCL mapping
    • pull-ups
    • logic level compatibility
  3. Only after the bus is electrically plausible, check address, device mode, and library expectations.
  4. If the board is Uno R4 family and the failure involves board-specific I2C or support questions, also open ../../docs/board-support/uno-r4-family.md.

Core Rules

  • Scanner success does not prove the library is using the device correctly.
  • Library failure does not prove the sensor is dead.
  • Bus voltage, pull-ups, and pin mapping must be explicit before changing code blindly.
  • For ESP32-family boards, pin choices and multi-bus assumptions are not always portable across variants.

Verification

  • Confirm whether the scanner sees the expected address.
  • Confirm whether a minimal register or identification read works.
  • Confirm whether the failing behavior tracks a board family, bus instance, or library rather than the sensor alone.
  • Confirm whether the final fix survives repeated scans and actual sensor reads.

Read the full file on GitHub · 79 lines

Files

What ships with it

3 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 · 79 lines · 64 tokens per session scan A b06951c7b3a3

Subscribe to this mod's changes

i2c-bringup-diagnostician is a skill published in the GitHub repository wedsamuel1230/arduino-skills (21 stars, last pushed 23d ago), licensed MIT. It adds 64 tokens to every session and 729 once invoked, about $0.0003 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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