About BTC-TKP
The FatCat Protocol
What Is BTC-TKP?
BTC-TKP (Bitcoin Telephone Keypad) is a minimalist, stack-based programming language designed for creating Bitcoin transactions using only 12 buttons: 0-9, *, and #.
It's a Bitcoin "assembly language" that works on any hardware with a telephone keypad - no touchscreens, no keyboards, just 12 simple buttons.
Why Telephone Keypads?
Telephone keypads are:
- Universal - Found worldwide on phones, ATMs, door locks, and vending machines
- Accessible - Tactile feedback, large buttons, familiar layout
- Cheap - Cost under $10, widely available from industrial suppliers
- Durable - Metal keypads can last decades in harsh environments
- Air-gappable - No WiFi, Bluetooth, or USB needed for secure signing
Use Cases
Hardware Wallets
Build DIY Bitcoin signing devices with RFID authentication and QR code display. Air-gapped security without expensive components.
Vending Machines
Accept Bitcoin payments using existing keypad hardware. No screen upgrades required.
ATMs
Add Bitcoin send/receive to cash ATMs using their built-in keypads and receipt printers.
Door Locks
Lightning Network payments for smart locks, parking gates, and access control systems.
Educational
Teach Bitcoin transaction structure with hands-on stack manipulation and real-time visualization.
Embedded Systems
IoT devices, payment terminals, and industrial equipment with minimal UI requirements.
The Philosophy
BTC-TKP follows the Unix philosophy: do one thing and do it well.
- Minimalism - Only essential commands, no bloat
- Transparency - See exactly what your transaction does
- Accessibility - Anyone can build Bitcoin applications
- Open Source - MIT licensed, fork and modify freely
Project Components
1. Web IDE (This Site)
A browser-based development environment for writing and testing BTC-TKP scripts:
- Virtual 12-button keypad interface
- Real-time syntax validation
- Stack visualization
- TEST mode with 5M mock satoshis
- Script import/export (
.btctpkfiles) - Sample programs library
2. ESP32 Hardware Wallet
Open-source firmware for building physical Bitcoin signing devices:
- Metal RFID keypad (12 buttons + contactless authentication)
- OLED display for stack and QR codes
- Air-gapped operation (WiFi/Bluetooth disabled)
- BIP39/BIP32/BIP44 wallet support
- Complete build guide with ~$40-60 parts list
3. The Language Specification
BTC-TKP is a complete stack-based language with:
- Number input (0-9 build values)
- Stack operations (
*push,*1peek,*2swap) - Bitcoin commands (
#1-#9for address scanning, signing, broadcasting) - Comment support (any text not matching command patterns)
- File format (
.btctpkfor portability)
Who Built This?
The FatCat Protocol was created by Bitcoin Fat Cat, with the goal of making Bitcoin more accessible to embedded systems and DIY hardware builders.
This is an open-source project released under the MIT License. You're free to use, modify, and distribute it however you like.
Get Involved
Want to contribute or build something with BTC-TKP?
- GitHub - Fork the repository
- Hardware - Build your own ESP32 signing device
- Integrate - Add BTC-TKP to your vending machine, ATM, or IoT project
- Feedback - Report bugs, suggest features, share your builds
Support This Project
BTC-TKP is free and open source. If you find it useful, consider supporting development:
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