What is cypher-pn532 CLAUDE.md?

Project instructions for building and flashing firmware for a handheld NFC/RFID device based on an ESP32-C3 and PN532 module. Firmware is software that runs directly on hardware.

Use it to locate the canonical firmware, configure Arduino IDE or its command-line equivalent, install dependencies, and work with the device's NFC, display, SD card, and buttons.

It records the project's hardware wiring, source-file locations, board settings, and required libraries so code changes can be built for the correct device.

How dkyazzentwatwa/cypher-pn532 configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to dkyazzentwatwa/cypher-pn532. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/dkyazzentwatwa/cypher-pn532/main/CLAUDE.md

Clone the repo

git clone --depth 1 https://github.com/dkyazzentwatwa/cypher-pn532

Made for: Claude Code.

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.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/dkyazzentwatwa/cypher-pn532/claude-md/github.svg)](https://agentmods.dev/instructions/dkyazzentwatwa/cypher-pn532/claude-md)

Your own site

<a href="https://agentmods.dev/instructions/dkyazzentwatwa/cypher-pn532/claude-md"><img src="https://agentmods.dev/badge/instructions/dkyazzentwatwa/cypher-pn532/claude-md/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.

Your own site · 80×15

<a href="https://agentmods.dev/instructions/dkyazzentwatwa/cypher-pn532/claude-md"><img src="https://agentmods.dev/badge/instructions/dkyazzentwatwa/cypher-pn532/claude-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 2,802 This file is loaded in full into every session.

When invoked 2,802 The same file — it is already loaded in full.

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.

Model	Per session	Once invoked
Fable 5.1	$0.02802	$0.02802
Opus 5.5	$0.01121	$0.01121
Sonnet 5.5	$0.00560	$0.00560
Haiku 4.5	$0.00280	$0.00280

Measured 2mo ago against content hash 97358629ec98, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

cypher-pn532 CLAUDE.md 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 2mo 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.

CLAUDE.md · 189 lines

How it starts

The opening of the file, as written. The whole thing — 189 lines — stays where its author put it; the contents beside it link to each section on GitHub.

CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Project Overview

Cypher PN532 is an Arduino firmware for an ESP32-C3 Super Mini-based NFC/RFID handheld device and open PN532 field workstation. The canonical ESP32-C3/Cypherbox source is cypher_pn532/cypher_pn532.ino; the Cardputer port mirrors workstation behavior in CardputerPN532/CardputerPN532.ino.

Hardware

Component	Pin(s)
PN532 NFC module (I2C)	IRQ=2, RESET=3
SSD1306 128x64 OLED (I2C)	I2C address 0x3C, SDA=8, SCL=9
SD card (SPI)	CS=10, MOSI=6, MISO=5, SCK=4
Button UP	GPIO 7 (rewired from 3 — was conflicting with PN532_RESET)
Button DOWN	GPIO 1
Button SELECT	GPIO 0 (rewired from 2 — was conflicting with PN532_IRQ)

Build & Flash

Open cypher_pn532/cypher_pn532.ino in Arduino IDE 2.x. Select board: XIAO_ESP32C3 (Tools → Board → ESP32 Arduino → XIAO_ESP32C3). CLI FQBN: esp32:esp32:XIAO_ESP32C3:CDCOnBoot=cdc,PartitionScheme=huge_app.

Required libraries (install via Library Manager):

Adafruit PN532
Adafruit GFX Library
Adafruit SSD1306
U8g2_for_Adafruit_GFX
NimBLE-Arduino
SD (built-in ESP32 SD library)

Serial debug output at 115200 baud.

Workstation Control Surfaces

All variants expose foreground NFC operations through device menus, USB serial commands at 115200 baud, a manually launched no-auth Web Control AP at http://192.168.4.1, and menu-launched no-auth BLE Serial using Nordic UART Service as CYPHER-PN532.

USB/BLE/Web operations use these names: HELP, STATUS, SCAN, DUMP, KEY_AUDIT, WRITE_NDEF, WRITE_FROM_SD, CLONE, VERIFY, FILES, GET_FILE, PUT_PRESET, DELETE, and EMULATE_NDEF. Arguments are key=value tokens with percent-encoded values; responses are newline-delimited JSON. The host helper is tools/cypher_pn532_cli.py.

Web Control intentionally has no HTTP auth and includes destructive controls. Keep it device-launched and lab-scoped; do not make it auto-start in setup(). BLE Serial intentionally has no pairing/app auth and includes destructive controls. Keep it menu-launched only; do not make it auto-start in setup().

Read the full file on GitHub · 189 lines

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.

2mo ago First seen · 189 lines · 2,802 tokens per session scan A 97358629ec98

Subscribe to this mod's changes

cypher-pn532 CLAUDE.md is an instructions file published in the GitHub repository dkyazzentwatwa/cypher-pn532 (55 stars, last pushed 3mo ago), licensed Apache-2.0. It adds 2,802 tokens to every session, about $0.0112 per session on Opus 5.5. 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.

Hardware and IoT

cypher-pn532 CLAUDE.md next to 6 instructions from other repositories
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cypher-pn532: Instructions file for Claude Code