TI-84 AI

Custom firmware for a modded TI-84 Plus with an internal Seeed Studio XIAO ESP32S3 Sense and OV5640 camera.

The calculator talks to the ESP32 over the 2.5mm TI link port. The ESP32 handles WiFi, camera capture, and OpenAI requests. A small TI-BASIC program called TIAI runs on the calculator as the UI.

Features

• Send typed prompts to a vision-capable OpenAI model from the calculator
• Reply to continue a conversation with context from previous messages
• Take a photo and have it solved automatically
• Scroll through long responses line by line
• Web config portal for WiFi, API key, camera quality, and debug AP settings
• Three camera quality profiles: Fast (VGA), Balanced (SXGA), Sharp (UXGA)
• Camera debug hotspot (TI84CAM) with live preview page on port 81
• Toggle the debug AP on or off from the config portal
• Settings stored in ESP32 flash (NVS) and persist across reboots
• One-command program install via Send({1}) with automatic retry
• Auto-reconnect and DNS recovery for flaky WiFi

Hardware

Part	Details
Calculator	TI-84 Plus (non-CE)
Microcontroller	Seeed Studio XIAO ESP32S3 Sense
Camera	OV5640
Connection	Internal wiring to calculator link port

This is a custom internal hardware mod, not a general-purpose accessory.

Wiring

TI Link Pin	ESP32 Pin
Tip	D0
Ring	D1

See include/config.h and include/camera_pins.h for the full pin definitions.

Repo Layout

include/
  config.h            - link pins, prompts, model, camera settings
  camera_pins.h       - OV5640 pin mapping
  program_data.h      - generated tokenized TI-BASIC program
src/
  main.cpp            - TI link handling and command dispatch
  camera.h            - camera capture and preview helpers
  wifi_manager.h      - WiFi, config portal, debug AP, and camera debug server
  openai_client.h     - OpenAI Responses API client with retry and DNS recovery
  web_ui.h            - config portal HTML rendering
tools/
  build_program.py    - TI-BASIC source and tokenizer
  capture_serial.ps1  - serial log capture (timed, auto-detects COM port)
  start_capture_background.ps1 - start serial capture in a background process
  stop_capture_background.ps1  - stop the background capture process
platformio.ini        - PlatformIO environment

Development Setup

You need three things installed before you can build:

1. Python 3 -- https://www.python.org/downloads/
2. Git -- https://git-scm.com/downloads
3. PlatformIO
   • Option A: install the PlatformIO IDE VS Code extension
   • Option B: install PlatformIO Core for command-line builds (pipx install platformio)

After installing PlatformIO, open this project folder in VS Code or in your shell.

If you use the VS Code extension you do not need to install PlatformIO Core separately.

PlatformIO docs: VS Code extension | Core installation

Build and Flash

Build the firmware:

platformio run

Flash to the ESP32:

platformio run --target upload

List connected serial devices if PlatformIO does not auto-detect the board:

platformio device list

Flash to a specific port if needed:

platformio run --target upload --upload-port /dev/ttyACM0

Open the serial monitor:

platformio device monitor --baud 115200

Or target a specific port:

platformio device monitor --port /dev/ttyACM0 --baud 115200

On Linux, if upload or monitor fails with Permission denied, add your user to the dialout group and sign out/in before retrying:

sudo usermod -aG dialout "$USER"

First-Time Calculator Setup

Once the ESP32 is flashed, set up the calculator:

1. On the TI-84 home screen, type Send({1}) and press ENTER.

   To find Send(: press [2ND] > [CATALOG] > [LN] > scroll to Send(

   This installs prgmTIAI on the calculator.

2. Run prgmTIAI.

3. Go to SETTINGS > CONFIGURE. The calculator will display an AP name.

4. On your phone or computer, connect to the TI84AI network (password: 12345678).

5. Open the config page that appears and enter:

   • WiFi network name (SSID) and password
   • OpenAI API key
   • Camera quality profile (optional, defaults to Balanced)
   • Whether to enable the TI84CAM debug hotspot (optional, on by default)

6. Save. The ESP32 will reboot with the new settings.

7. Back on the calculator, go to SETTINGS > CONNECT.

You're ready. Use SEND MESSAGE to type a prompt, REPLY to follow up, or TAKE PHOTO to snap and solve. Scroll through long responses with the up/down keys.

When finished, pop out a battery to completely kill power to the ESP32. A 1.5V or 1.2V battery works.

Camera Debug Hotspot

When enabled and connected to WiFi, the ESP32 also starts a secondary AP called TI84CAM (password: 12345678). Connect to it and visit http://192.168.8.1:81/ to see a live camera preview. The debug AP can be toggled on or off from the config portal.

Updating the Embedded TI-BASIC Program

If you edit the TI-BASIC source in tools/build_program.py:

python3 tools/build_program.py         # regenerate the tokenized program
platformio run --target upload         # flash the updated firmware

Then on the calculator, run Send({1}) again to install the new version of TIAI.

Notes

• Camera quality, model, and prompt behavior are configured in include/config.h
• The OpenAI client uses the Responses API (/v1/responses) with conversation state via previous_response_id
• Vision requests are built manually (not via ArduinoJson) to avoid duplicating large base64 strings in RAM
• Serial logs are not committed because they may contain local network details

Known Limits

• Built for the TI-84 Plus, not the TI-84 Plus CE
• Large image uploads can stress the ESP32 network stack
• The silent install path may log No ACK after EOT even on a successful install
• Vision requests do not carry conversation history (each photo is standalone)