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ASCII to Scan Codes Converter

Converts ASCII text into standard PS/2 Set 1 keyboard make-scan-codes (one hex byte per physical key pressed), representing shift-required characters like uppercase letters and shifted symbols as the Left-Shift make code 2A followed by the base key's scan code. A free online tool from Staaarter, right in your browser.

Runs locallyUpdated 2026-07-27
keyboardlow-levelconversion

Overview

Introduction

Long before USB HID reports, PS/2 keyboards communicated every keypress as a scan code, a single hex byte identifying the physical key, using a standard layout still referenced constantly in low-level OS development and embedded firmware work.

This tool converts ASCII text into the sequence of PS/2 Set 1 make-scan-codes a US QWERTY keyboard would send to type it, including the real shift-prefix convention for uppercase letters and shifted symbols.

What Is ASCII to Scan Codes Converter?

A text-to-scan-code encoder built on the classic PS/2 Set 1 make-code table (the same table used by the original IBM XT/AT keyboard controller and still emulated by virtually every PC-compatible keyboard today).

It distinguishes base (unshifted) keys from shift-required characters: a lowercase letter or digit is one scan code byte, while an uppercase letter or shifted symbol is the Left-Shift make code (2A) followed by the base key's byte.

How ASCII to Scan Codes Converter Works

The input is validated as strict 7-bit ASCII, then each character is checked against the base scan-code table (letters, digits, space, and common punctuation) or, for uppercase letters and shifted symbols, resolved to its unshifted base key first.

Shift-required characters are prefixed with the Left-Shift make code 2A before the base key's byte; characters with no reasonable physical key on a standard layout are rejected with an error naming the character and position.

When To Use ASCII to Scan Codes Converter

Use it when working with low-level keyboard driver code, OS development tutorials, or embedded firmware that processes raw PS/2 scan codes directly.

It's also useful for generating test input sequences for a keyboard controller emulator or for understanding exactly what bytes a real keyboard sends for a given string.

Often used alongside Scan Codes to ASCII Converter, ASCII to Keycodes Converter and ASCII to Hex Converter.

Features

Advantages

  • Implements the real, standard PS/2 Set 1 make-code table rather than an invented scheme.
  • Correctly represents shift-required characters using the genuine two-byte shift-prefix convention real keyboards use.
  • Reports precisely which character and position triggered a rejection when no reasonable physical key exists.

Limitations

  • Only generates make codes (key-down); it doesn't model break codes (key-up) or the timing/ordering of a real key-press sequence.
  • Covers letters, digits, space, and common punctuation only; function keys, arrow keys, and other non-printable keys aren't in scope since there's no ASCII character to drive them from.

Examples

Encoding lowercase text

Input

hi

Output

23 17

"h" and "i" are both base (unshifted) keys, each producing exactly one scan-code byte.

Encoding an uppercase letter

Input

Hi

Output

2A 23 17

"H" needs Shift, so it's represented as the Left-Shift make code (2A) followed by the "h" key's base scan code (23); "i" stays a single byte.

Encoding a shifted symbol

Input

1!

Output

02 2A 02

"1" is the base key's own scan code (02); "!" shares that same physical key but requires Shift, so it's 2A followed by 02 again.

Best Practices & Notes

Best Practices

  • Remember scan codes model physical keys, not characters, so a mixed-case round trip through this tool and its decoder preserves case correctly, unlike keyCode-based tools.
  • If you need break codes too, add 0x80 to each base byte in the output yourself; this tool intentionally only models the make (press) sequence.

Developer Notes

The base table is a fixed array of [character, hex] pairs taken from the standard PS/2 Set 1 make-code layout (letters/digits/punctuation in their conventional row order). Shifted characters are resolved through a SHIFTED_SYMBOL_TO_BASE lookup (e.g. "!" -> "1") before the base lookup, then prefixed with the literal Left-Shift code "2A"; scan-codes-to-ascii-converter imports this same table and inverts it so both tools share one source of truth.

ASCII to Scan Codes Converter Use Cases

  • Generating test input for a PS/2 keyboard controller emulator or OS-development keyboard driver
  • Understanding exactly which bytes a physical keyboard sends for a given string, shift prefix included
  • Cross-referencing scan-code values while following a low-level keyboard-driver tutorial

Common Mistakes

  • Assuming a scan code changes based on Shift state; it doesn't, the base key's code is constant, Shift state is communicated by a separate Left-Shift make/break code.
  • Forgetting the Left-Shift prefix is a real, separate byte in the sequence, not an attribute encoded into the following byte.

Tips

  • Round-trip through Scan Codes to ASCII Converter to confirm mixed-case text and shifted symbols decode back exactly, since this format (unlike keyCode) does preserve case.
  • The Left-Shift make code 2A is always literally "2A" in the output; look for it to spot every shift-required character at a glance.

References

Frequently Asked Questions