It was just that simple. Thank you! It's working great.

@jthomas5150 If you press F4 in emulationstation then you can quickly find out how your keyboard is configured (by trial and error). For example on my big keyboard almost none of the symbols on my keyboard coincide with the symbols that appear on my tv screen when I press them.

Depending on game, you may need to change the machine - some will work only on 400/800, 800XL (64) or 130 XE. Other thing that often helps is to "enable BASIC on boot" in options.

Of course you need to have all the appropriate bioses in the right place/detected too.

@mitu Thanks for replying. My gamepads mirror each other, and have the same number of buttons installed and mapped to the same keys. I'm aware that the gamepads won't work correctly if there are any differences at all. In fact, I had to add two extra buttons to the player 2 USB encoder in order to make it mirror the player 1 USB encoder precisely. Initially, we had installed two extra joypad 1 buttons to serve as a hotkey/escape and as a pause button, but they wouldn't work without identical buttons set up in joypad 2. The joypad 2 buttons are actually inside of the cabinet, because there are no holes for them on the control panel. I've already used jstest many times, too. So, I can promise that the two joypads are configured identically, and I haven't set up any player 1 buttons in the 800/5200 emulator that map differently from player 2. I know better.

I really do think the problem is that the Atari 5200 emulator isn't yet set up to recognize multiple fire buttons for player 2. I found a discussion on this forum from May 2016 entitled "Atari 5200: New version of Atari800 (Beta): two triggers (Moon Patrol), hat start and exit buttons" where user jfroco discussed a new port of Atari800 that added trigger1, trigger2, asterisk and hash support for joystick buttons, but only for player 1. A later post from user Veramacor (April 2017) detailing atari800.cfg settings also reflected trigger1 and trigger2 support on Joystick 0, but not Joystick 1. Then, in May 2017 user Used2BeRX asked user future.child if they would be able to properly code the player 2 controller to allow two-player games. It's not clear from the subsequent conversation that this ever got done in the way I'm discussing here.

I'm guessing from this discussion and my experiences this weekend that the Atari800 emulator must still be in that same developmental place, because when I tested the 5200 Moon Patrol ROM (I do own an original cartridge), sure enough, player 1 could use the second trigger (button X on my arcade cabinet config), but not player 2. The X button did nothing for player 2. Again, I'm not having this problem in any of the other emulators I'm using with Retroarch (MAME2003, MAME 2003-Plus, Final Burn Alpha, MAME2010, Stella, CoolCV, or the NES and SNES emulators). On those emulators, all buttons work the same for both gamepads. There are no discrepancies.

However, if someone can verify that they are able to use both fire buttons for both player 1 and player 2 in Atari 5200 Moon Patrol (one to fire, one to jump), RealSports Football, etc., I will be more than happy to try to get it working for Player 2 in Retropie. I just haven't seen anyone confirm that there is trigger1, trigger2, * and # support for Player 2 in the 5200 emulator. The only evidence I've found is that there isn't such support, and I don't want to spend days futilely trying to set up something that isn't actually supported. In fact, a post from three months ago said that the controller upgrades future.child made from 2016-18 aren't part of the current libretro version of atari800. (That thread also suggested that RealSports Football is viewed as a lost cause because of its need for keypad input.) Maybe the best way to ask this question is, does Moon Patrol work properly for player 2 on the 5200? Can you jump and fire?

The gui isn't letting me map keys to buttons - I can map controller buttons to key strokes but I think the 5200 emulator is looking for input from a keypad and not a keyboard - I'm really new to this, so I'm probably missing something simple.

Thanks. I will look in the future.

You nailed the concern on this perfectly by describing the fact the Colecovision, Intellivision and Atari 5200 (CX52) have very similar controllers. What I really wish is that the three communities would get together and do a Kickstarter or GoFundMe to develop an improved, common controller that can be used with all three systems. I don't know what other consoles used a numeric keypad as part of the controller. It's fairly unique compared to all modern controllers made in the last 35 years. I think when NES came out in 1985, those type controllers started to disappear from production. By thinking in terms of a common controller for all three systems, it seems a lot more feasible to do than just going it alone for just one system.

My idea would be to make the controller flexible to serve all three consoles. I'm an Intellivision fan, so the numeric touchscreen could be flipped upside down (software config) for Colecovision and Atari 5200 fans whose controllers had the numeric keypad on the bottom (the three buttons above the CX52 joystick would have to be combined onto the 15-button touchscreen - a compromise). The four side buttons could be near the middle of the controller (another compromise). Both ends of the controller would have ports for connection to the homebrew console or PC with different cable adapters. Configuration software would be created to program the controller to immediately act as a duplicate of one of the three console's controllers. The directional disc itself could be configurable with attachments to closely represent each console.

@future-child said in Atari 800 setup is nightmarish:

It does however lack an entry for A800 in retropie but editing /opt/retropie/configs/all/emulationstation/es_systems.cfg will fix that

Only reason why it's missing is that no one ever confirmed a800 working and with what parameters.

I’ll add this to the docs. It does say to select Atari Joystick, but it’s down in the lr-Atari emulator section and 5200 users may not read to there though they should.

@used2berx

Hey I had Space invaders on my Atari 800 xl (same as 5200)
It was unique yes, but for me, the 2600 version was the best !
Actually I even prefer the 2600 version over the original arcade ;)

@RockyMtnBri Not without significant development. It's windows only, there currently isn't a macos or linux build. As a minimum someone would have to create an sdl2 gui for it.

Sorry to hijack. I never knew that an alternative fork of the highly complicated A8 emu for retropie existed! Thanx for the info. I will have a try

Thanks. I had to install as optional package. I followed the rest of video. Feels like getting a old hardware to work give the amount of time you need to setting Atari 5200 :)

Is a system to play more out of curiosity. And i love the AVGN Atari 5200 video.

Thanks herb, I did read that part but failed to see where it said anything about atari5200 not being installed. I guess I assumed it was since both atari 2600 and 7800 were, and it wasn't mentioned in https://github.com/RetroPie/RetroPie-Setup/wiki/Atari-800-and-5200