A500 Mini - 9 Pin Joystick to USB Adapter Guide

As of firmware version 1.2.1 you can now supply a custom controller configuration file on the root of any FAT32 connected file system.

Firstly you'll need to follow the firmware update guide outlined on the official website.

https://retrogames.biz/support/thea500-mini/manuals/update-1-2-1/

then once you have updated the firmware you'll want to create a file named gamecontrollerdb.txt in the root of the connected USB drive. In there you'll want to add the following information.

03000000591c00002300000010010000,Retro Games LTD THEJosytick Original Joystick,b:b1,a:b0,back:b6,leftshoulder:b4,leftx:a0,lefty:a1,rightshoulder:b5,start:b7,x:b2,y:b3,platform:Linux,
03000000591c00002400000010010000,Retro Games LTD THEJoystick MicroSwitch Joystick,b:b1,a:b0,back:b6,leftshoulder:b4,leftx:a0,lefty:a1,rightshoulder:b5,start:b7,x:b2,y:b3,platform:Linux,
03000000591c00002600000010010000,Retro Games LTD THEGamepad,a:b2,b:b1,x:b3,y:b0,back:b6,start:b7,leftshoulder:b4,rightshoulder:b5,leftx:a0,lefty:a1,platform:Linux,

And then depending on what adapter version you are using add the following line.

Version 2

03000000eb030000f42f000011010000,Monster Joysticks Ltd. DE9 to USB V2,a:b0,b:b1,back:b6,leftx:a0,lefty:a1,leftshoulder:b4,rightshoulder:b5,start:b7,x:b3,y:b2,platform:Linux,

Version 1

03000000c0160000dc27000001010000,Monster Joysticks MJ2DB9,a:b1,b:b4,back:b6,leftx:a0,lefty:a1,leftshoulder:b0,rightshoulder:b5,start:b7,x:b3,y:b2,platform:Linux,

You can then connect the USB media to the A500 Mini, restart it and your adapter should be detected and useable.