TACT - Touch-Activated Calculator for the Blind

TACT – Touch Activated Calculator for The Blind is a low-cost, standalone device that makes everyday math fully accessible to blind and low-vision users — no phone, no PC, and no sighted help required. Built on the STM32F411E microcontroller, it turns a simple phone-style keypad into a calculator you can operate entirely by ear and by touch.



Every key press and every result is spoken aloud through a built-in speaker, with bilingual voice output that switches instantly between English and Vietnamese. Press a new key while an answer is being read, and the speech cuts off and responds immediately — so the device feels quick and natural, never laggy. Beyond basic arithmetic, it handles scientific functions and solves quadratic equations, reading both roots aloud.

What sets it apart is its refreshable braille line: results are rendered as raised braille dots, letting users read the answer with their fingertips — combining audio and tactile feedback in a single self-contained unit. An optional LCD mirrors the output for sighted assistance.

Affordable, reproducible, and built from widely available components, it demonstrates that genuinely useful assistive technology can be delivered on everyday microcontroller hardware — putting independent calculation back within reach.