TI-84-GPT-HACK

A graphing calculator with a network sidecar.
An ESP32 speaks the TI link protocol, makes web requests, and sends text, programs, and 96×63 images back as calculator variables.

Watch the repository demo

This is a hardware and protocol research project—not an exam aid. Follow your school’s device and academic-integrity rules.

What it can do

• Ask an OpenAI-compatible model questions with persistent chat sessions
• Page long text responses on the calculator screen
• Connect through a phone-friendly captive portal, including WPA2-Enterprise networks
• Scan and select nearby Wi-Fi networks from the calculator
• Download calculator programs and 96×63 monochrome images
• Update both ESP32 firmware and the calculator launcher over the air
• Serve a built-in AP Physics C E&M reference without a network request
• Run GPT-backed physics and math prompts
• Expose a Telnet serial monitor over the local network
• Sleep after two minutes of inactivity and wake when the calculator sends a command

The link-port trick

TI-BASIC launcher
       │ command + arguments as TI variables
       ▼
TI-84 link port ── TIP / RING ── ESP32
                                      │
                         Wi-Fi / HTTPS / OTA
                                      │
                                      ▼
                    GPT API · firmware · programs

The ESP32 uses CBL2, TICL, and TIVar to behave like another calculator. The launcher sends a command ID and arguments; firmware performs the network or local operation, then returns a TI string, number, picture, or program. The calculator never needs to understand HTTP.

Project layers

Layer	Responsibility
programs/ANDYGPT.8xp	calculator menus and interaction
esp32/esp32.ino	link protocol, Wi-Fi, commands, sleep, and OTA
server/	GPT, program, image, firmware, log, and request routes
pcb/	KiCad board, schematic, Gerbers, and build photos
compile_launcher.py + scripts	prepare launcher and firmware assets

Use the existing build

The firmware currently points to https://api.andypandy.org.

1. Run ANDYGPT on the calculator.
2. Open Settings → SETUP.
3. Join the temporary Wi-Fi network named calc from a phone or computer.
4. Use the captive portal—or open 192.168.4.1—to save network credentials.
5. Return to the launcher and choose a connected feature.

The ESP32 stores Wi-Fi credentials for later boots. For mixed-case input on the TI-84 keyboard, letters are lowercase by default and parentheses mark uppercase letters: (H)ELLO becomes Hello.

Build your own hardware

The KiCad sources, schematic, Gerbers, firmware, and calculator programs are included. A detailed assembly tutorial is intentionally out of scope: this build involves a custom PCB, fine-pitch hardware work, and a timing-sensitive calculator bus. It is not a first soldering project.

At the software level:

1. Open esp32/esp32.ino in Arduino IDE.
2. Install the ESP32 board support and the libraries included by the sketch: TICL, CBL2, TIVar, and UrlEncode.
3. Flash the firmware to the ESP32 target used by your board.
4. Transfer programs/ANDYGPT.8xp to the TI-84, or use the launcher update path once the bridge is working.

If you change hardware, verify the TIP and RING pin definitions before powering the interface.

Run a private server

The backend requires Node.js 18 or later, an OpenAI-compatible API, and S3-compatible object storage for chat and firmware state.

cd server
npm install

Create server/.env:

OPENAI_API_KEY=your-key
OPENAI_BASE_URL=
LLM_MODEL=gpt-5.4-nano
LLM_MODEL_MATH=

R2_ENDPOINT=https://your-account.r2.cloudflarestorage.com
R2_ACCESS_KEY_ID=your-access-key
R2_SECRET_ACCESS_KEY=your-secret-key
R2_BUCKET_NAME=your-bucket

OPENAI_BASE_URL and LLM_MODEL_MATH are optional. Keep .env out of version control.

Run locally:

npm start

The default local port is 8080. Change the SERVER definition near the top of esp32/esp32.ino to the HTTPS URL of your deployment, then reflash.

AP Physics C E&M mode

The launcher includes local reference branches for equations, derivations, field and circuit behavior, common graphs, and right-hand-rule mnemonics. These static references do not require Wi-Fi. The SOLVER branch sends numeric or free-form prompts to the configured model.

Use ◀/▶ to move through long pages and CLEAR to return. Type expressions in plain words when possible; many special TI math glyphs do not decode cleanly over the current link layer.

Updates

From Settings → UPDATE, the ESP32 checks the server’s firmware version, downloads a newer binary when available, reboots, and can push the updated launcher back to the calculator.

Firmware artifacts and launcher data are stored through the server’s S3-compatible storage layer. Protect upload routes if you deploy the backend publicly.

Known limits

• Link communication is timing-sensitive; retry or power-cycle both devices after a stalled transfer.
• The ESP32 radio requires 2.4 GHz Wi-Fi.
• Image transfer is experimental and not consistently reliable.
• TI tokens for complex math symbols are only partially decoded; plain-text math is safer.
• Several lower-level math and utility handlers remain in firmware even though the current launcher does not expose them.
• The optional camera code is disabled by default.

Origin and license

The concept was inspired by ChromaLock’s 2024 video. This reconstruction, firmware, PCB design, server, and launcher are maintained by Andy / ChinesePrince07.

Licensed under the GNU GPL v3.