It's already been about a fortnight since I received the prototype PCB for the adapter version Atari PS/2 Eiffel with joystick ports. I took the opportunity to correct a few (minor) design errors for the next PCB version, but I was faced with a problem: The joystick's firing button wasn't working..
In any case, that's what I've found when using Mouse and Joystick Tester, a mouse and joystick testing software under GEM, developed by Opera and available on the Atari forums: https://www.atari-forum.com/viewtopic.php?t=15942 and on its website: https://atari.8bitchip.info/astopensw.php as well as in the game Falcon In Spectrum Holobyte.
As the movements of the joystick 0 and from joystick 1 as well as mouse movements and clicks were detected, the fire button did not seem to be taken into account. Yet I was sure of both my joystick (the Atari CX40 model supplied with the 2600, yes I know...) and the’Atari Mega ST4 which serves as my test machine as everything worked with the original keyboard, the Atari mouse and the joystick plugged into it.
I then compared the original schematics with mine and the PCB several times; normally, everything should have worked. I even recreated the circuit on a breadboard just to check the joystick's fire button: same result! I also verified that the PIC was receiving the information of the pressed button and translating the order to the Atari using an oscilloscope. And it was the case, the PIC seemed to be receiving the button press correctly, and was transmitting a frame to the Atari. The origin of the malfunction was quite simply incomprehensible !
I was then ready to contact the creator of the Eiffel adapter., Didier Mequignon http://didier.mequignon.free.fr/ thinking that perhaps the PIC firmware was buggy for the joystick's fire button part...
While researching IKBD (the communication protocol for Atari keyboards and joysticks) which the Eiffel adapter emulates, I noticed that there exists Multiple joystick support modes, and that according to Didier's documentation, the IKBD_SET_FIRE_BUTTON_MONITOR mode is not supported by the Eiffel. So a first clue that perhaps The joystick isn't perfectly emulated by the Eiffel.
Then I realised that I had only tested the joystick function through two pieces of software: Mouse and Joystick Tester and the game Falcon. What if these pieces of software specifically use this incompatible mode?
I then tested the PCB with several games (Robotron, Star Raiders, etc.), which I should have done long ago and... the joystick works perfectly from the start! However, for other games the joystick is not supported.
I will therefore add a warning to the sale of the PCB:
Attention: the Joystick function of the Eiffel adapter does not seem to work with all games!
With the exception of... keyboard and mouse functions, they work in games.
The new version of the PCB has been Go live, so the Eiffel adapter’s availability won’t be long now.