What is cypher-pn532 AGENTS.md?

A set of instructions for coding agents working on Cypher PN532, Arduino firmware for an ESP32-C3 handheld NFC/RFID device. It documents the device hardware, connections, required libraries, and how to build and flash the firmware.

Use it when modifying the firmware, connecting the PN532 reader, display, SD card, or buttons, or uploading code to the ESP32-C3.

It reduces guesswork about which source file, board settings, pins, and libraries the device uses. This helps avoid hardware conflicts and incorrect uploads.

How dkyazzentwatwa/cypher-pn532 configures Codex and OpenCode

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/AGENTS.md

Clone the repo

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

Made for: Codex, OpenCode.

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/agents-md/github.svg)](https://agentmods.dev/instructions/dkyazzentwatwa/cypher-pn532/agents-md)

Your own site

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

Per session 2,410 This file is loaded in full into every session.

When invoked 2,410 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	$0.02410	$0.02410
Opus 5	$0.01205	$0.01205
Sonnet 5	$0.00482	$0.00482
Haiku 4.5	$0.00241	$0.00241

Measured 10d ago against content hash a9b057ee97f8, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

cypher-pn532 AGENTS.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 10d 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.

AGENTS.md · 159 lines

How it starts

The opening of the file, as written. The whole thing — 159 lines — stays where its author put it; the contents beside it link to each section on GitHub.

AGENTS.md

This file provides guidance to Codex (Codex.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 line protocol at 115200 baud
Device-launched no-auth Web Control AP at http://192.168.4.1
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 · 159 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.

10d ago First seen · 159 lines · 2,410 tokens per session scan A a9b057ee97f8

Subscribe to this mod's changes

cypher-pn532 AGENTS.md is an instructions file published in the GitHub repository dkyazzentwatwa/cypher-pn532 (48 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 2,410 tokens to every session, about $0.0120 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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