# FIXED ABXY face buttons on mGBA

**URL:** <https://forum.clockworkpi.com/t/fixed-abxy-face-buttons-on-mgba/21982>\
**Category:** uConsole\
**Tags:** tinkering, community, retroarch, software, uconsole\
**Created:** [March 29, 2026, 10:57pm UTC](https://forum.clockworkpi.com/t/fixed-abxy-face-buttons-on-mgba/21982 "2026-03-29T22:57:06Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Dr\_Dalek](https://yyz1.discourse-cdn.com/flex029/user_avatar/forum.clockworkpi.com/dr_dalek/32/16220_2.png) [@Dr\_Dalek](https://forum.clockworkpi.com/u/Dr_Dalek)\
**Post date:** [March 29, 2026, 10:57pm UTC](https://forum.clockworkpi.com/t/fixed-abxy-face-buttons-on-mgba/21982/1 "2026-03-29T22:57:06Z")

</div>

Heyy I found a fix and haven’t seen anything about it so I figured I’d write up about it here. I’m working on something rather big i’m planning on releasing soon, more to come on that later… but along the way I figured something out for myself. Hopefully it helps others? Maybe a community OS solves this and I’m just living under a rock… Anyway!

Spent a while debugging why the ABXY face buttons don’t work in mGBA on Bookworm even though the D-pad is fine. Turns out **SDL 2.26** (which Bookworm ships) quietly changed how joystick GUIDs work.

It now sticks a CRC16 into bytes 2-3 of the GUID. So the old mapping everyone’s been using (03000000af1e…) doesn’t match anymore.

The actual GUID on Bookworm is `030000fdaf1e00002400000010010000`. You can verify yours by saving this as `guid.py` on the uConsole (over SSH):

```python
import ctypes, ctypes.util

class GUID(ctypes.Structure):
    _fields_ = [('data', ctypes.c_uint8 * 16)]

sdl = ctypes.CDLL(ctypes.util.find_library('SDL2'))
sdl.SDL_JoystickOpen.restype = ctypes.c_void_p
sdl.SDL_JoystickGetGUID.restype = GUID
sdl.SDL_JoystickGetGUID.argtypes = [ctypes.c_void_p]
sdl.SDL_JoystickGetGUIDString.argtypes = [GUID, ctypes.c_char_p, ctypes.c_int]

sdl.SDL_Init(0x200)
js = sdl.SDL_JoystickOpen(0)
buf = ctypes.create_string_buffer(33)
sdl.SDL_JoystickGetGUIDString(sdl.SDL_JoystickGetGUID(js), buf, 33)
print(buf.value.decode())
sdl.SDL_Quit()

```

Then run it from a **local terminal on the uConsole** (not SSH — SDL can’t see the joystick over SSH):

```bash
python3 guid.py

```

Also found that the A/B buttons were swapped in the old mapping. Here’s what actually works - put this in your .profile or .bashrc:

```bash
export SDL_GAMECONTROLLERCONFIG="030000fdaf1e00002400000010010000,ClockworkPI uConsole,platform:Linux,a:b1,b:b2,x:b3,y:b0,back:b8,start:b9,dpdown:+a1,dpleft:-a0,dpright:+a0,dpup:-a1,"

```

For mGBA specifically (0.10.1 from apt), the SDL env var alone isn’t enough becuase it needs explicit button bindings in `~/.config/mgba/config.ini`:

```ini
[gba.input.SDLB]
keyA=1
keyB=2
keyStart=0
keySelect=3

[gba.input-profile.030000fdaf1e00002400000010010000]
keyA=1
keyB=2
keyStart=0
keySelect=3

```

The section names and key prefix are important and it took a while to figure that out. mGBA’s config format is not well documented for the SDL build.

A couple other things I learned along the way:

- The D-pad sends keyboard arrow keys, not joystick events. That’s why it works out of the box.

- ABXY fire as BTN\_TRIGGER through BTN\_TOP on evdev but don’t show up on /dev/input/js0 at all. this is probably written somewhere idk about.

- There’s no uConsole entry in the upstream SDL\_GameControllerDB yet

Have fun playing Pokemon hahaha

My system: CM4, Debian Bookworm, SDL 2.26.5, mGBA 0.10.1.