This guide demonstrates how to toggle between 400×240 and 320×240 resolutions during gameplay for 3DS titles using the Citra emulator on Batocera.

This is especially useful when:

• You want to play 3DS games in native resolution (400×240), preserving the system's original pixel layout.
• You want to switch to 320×240 for better fullscreen compatibility on 15kHz CRTs.

Enable in-game resolution switching for 3DS titles with a button combination, toggling between:

• Citra emulator installed and working
• Valid videomodes.conf entries for:
  • 400x240.60.00021
  • 320x240.60.00010
• evmapy enabled in Batocera
• SSH or file access to create/edit files
• Hotkey + X button available on your controller

Create a file at:

/userdata/system/configs/evmapy/3ds.keys

Paste the following JSON content:

{
    "actions_player1": [
        {
            "trigger": [
                "hotkey",
                "x"
            ],
            "type": "exec",
            "target": "/userdata/system/citra-resolution"
        }
    ]
}

This will bind HOTKEY + X to a custom script.

💡 The name 3ds.keys ensures the config applies to all 3DS games using Citra.

Create the following file:

/userdata/system/citra-resolution

Make sure it is executable:

chmod +x /userdata/system/citra-resolution

Paste the following content into the script:

#!/bin/bash

RES=$(batocera-resolution currentResolution)
case "$RES" in
    400x240) batocera-resolution setMode 320x240.60.00010 ;;
    320x240) batocera-resolution setMode 400x240.60.00021 ;;
esac

This script checks the current resolution and switches to the other.

📌 This script idea and logic were contributed by Bloodred217.

1. Launch a 3DS game from EmulationStation.
2. Once the game is running, press:

   HOTKEY + X
   

3. The resolution should switch instantly between 400x240 and 320x240.

📝 Use DISPLAY=:0 batocera-resolution currentResolution from SSH to verify resolution names if unsure.

This setup uses:

• evmapy to bind a controller input to a shell command.
• A Bash script that uses batocera-resolution to query and switch video modes.
• The video mode names must match entries in your videomodes.conf file.

The behavior is fully integrated into Batocera’s resolution handling system and works without restarting EmulationStation or the emulator.

• Double-check file permissions:

  chmod +x /userdata/system/citra-resolution

• Confirm the video modes exist using:

  DISPLAY=:0 batocera-resolution listModes

• Validate the names in videomodes.conf:

  400x240.60.00021:400x240 1.0:0:0 15KHz 60Hz
  320x240.60.00010:320x240 1.0:0:0 15KHz 60Hz
  

# Before toggle
batocera-resolution currentResolution
> 400x240

# After pressing HOTKEY+X
batocera-resolution currentResolution
> 320x240

💬 Have another emulator that could benefit from this technique? The same principle applies — just adjust the .keys file name and script logic.