GBA False Diagonal Test

Overview

This ROM can be used to test for diagonals and false diagonals. It works by detecting when a diagonal is pressed and showing an alert in the middle of the screen.

The glyphs on the left will light up in green when the corresponding direction is pressed, and the bottom middle has a rolling graph showing the history of button presses.

When a direction is locked, pressing a diagonal originating from that locked direction will show a "FALSE DIAGONAL" warning, indicating an unintentional diagonal was pressed.

Controls & Parameters

• D-pad: Press any direction and the corresponding glyph will light up green on the left side of the screen
• B: Change the rolling graph window size, in number of frames (120, 240, 360)
• L/R: Change the threshold (1 to 10), which is the number of frames a diagonal must be held to show the alert on-screen
• SELECT: Lock a direction for testing false diagonals (hold a direction while pressing SELECT to lock it)
• START: Reset on-screen counts

On-screen values

• THR: Frame threshold for recognizing a diagonal
• N: Window size (in frames) for the graph and ROLL values
• ROLL: The rolling count of diagonal frames across the last N frames
• COUNT: The total count of false diagonals
• U/D/L/R: The total count of each direction pressed

How to use

1. Launch the ROM in your emulator of choice
2. Confirm the THR and N values
3. Hold a direction and press SELECT to lock it
4. Rock the d-pad and test if there are false diagonals

Building

1. Download and install devkitPro (includes the GBA SDK and gcc cross-compiler): https://devkitpro.org/wiki/Getting_Started
2. During install, select (or afterwards install via dkp-pacman):

devkitARM
gba-dev (meta-package: libgba, templates, tools)

3. Verify env vars (the installer sets these):

   • DEVKITPRO points to devkitPro root
   • DEVKITARM is ${DEVKITPRO}/devkitARM

4. Make sure make and the ARM tools are on PATH. Quick check:

arm-none-eabi-gcc --version
echo $DEVKITPRO

5. make

Output: false_diagonal_test.gba

Note: A pre-compiled GBA ROM is provided so you don't need to install build dependencies.