Off for a trip to CPC land

[stephen_usher]

[rubber_jonnie]

Since playing with the CPC some more now I have the ULIfAC, which seems to work on a similar principle to the FreHD (I must finish that project!!), I've noticed a peculiar thing.

If I have a joypad/stick plugged in, I get random keypresses when sitting at the BASIC prompt. It appears to be the fire button being pressed. It doesn't happen when there is nothing plugged in.

So I did some testing last night, and the following sticks had this behaviour:

1. Atari 7800 joypads
2. Cheetah Mach 1
3. Atari Pro Line joystick
4. Sega Mega Drive Game Pad

The following worked just fine with no random keypresses:

1. Competition Pro
2. Sega Mega Drive Game Pad

I don't have others to test, but this struck me as odd, and likely a joystick issue, not a CPC issue. Those sticks that failed at the BASIC prompt worked just fine in games, and on other platforms, and they all have different mechanisms, so spring dome, microswitch, rubber dome etc.

I may have a look inside to see why the two that worked fine are different, and I am wondering if there are additional components that they have, that the others don't.

I'll just use the Game Pad for now as it suits me better than the Competition Pro, but I thought it odd and worth mentioning to see if anybody else had experienced this.

EDIT: The Mega Drive Game Pad is now on the naughty list after a bit more testing.

[PhilC]

@rubber_jonnie other than a ram upgrade, what does the UliFac do exactly and how much was it?

[rubber_jonnie]

@rubber_jonnie other than a ram upgrade, what does the UliFac do exactly and how much was it?

It offers the RAM upgrade, ROM slots, the possibility to set your CPC 464 into CPC1628, there is a serial port, USB port for thumb drives and floppy emulation, plus the option of WiFi. For €45 it's a bit of a bargain TBH and that included postage from Greece.

[stephen_usher]

Do the joysticks which show random key presses have auto-fire?

Also, the Amstrad joystick port is not quite Atari as it supports a second fire button or a second stick which has time sliced input selection I think. I guess that could be upsetting things.

[rubber_jonnie]

Do the joysticks which show random key presses have auto-fire?

Also, the Amstrad joystick port is not quite Atari as it supports a second fire button or a second stick which has time sliced input selection I think. I guess that could be upsetting things.

The Cheetah and Competition Pro do have auto fire, but the Cheetah has the problem, and the Competition Pro works just fine. None of the others have auto-fire. I had read that auto-fire requires 5v too, that the CPC doesn't provide on the joystick port.

Looking at the schematic, the joystick port is essentially an extension of the keyboard:

Screenshot 2023-11-05 at 10.24.31.png (526.89 KiB) Viewed 155 times

So any uncommanded inputs would show up as a keypress, what I'd like to understand is why the Competition Pro just works, but the others don't.

The Sega Game Pad was the strangest, as when plugged in, there were no random keypresses like with the others, but if you started typing it suddenly went mad and threw in loads of random keypresses.

Might open up a couple of them today and see why the CP is different.

[Icky]

Pull-ups in the joystick may be?

[rubber_jonnie]

Pull-ups in the joystick may be?

So I pulled the cover off all my sticks and had a look. None have pull ups of any sort and are all (bar the Sega) simply switches wired to the plug.

The Competition Pro is simply microswitches, as it the Cheetah Mach +. I realised just now that the Cheetah in fact works fine with the autofire turned off, I must have missed that the other day, and in fact internally it is very similar to the Competition Pro, so that's a bonus.

The Mega Drive Game Pad has some sort of glop top inside, so I will rule that out right away.

That leaves the Atari Pro line stick and 7800 joypad. These use the 'clicky domes' like this:

Screenshot 2023-11-05 at 17.16.25.png (538.22 KiB) Viewed 137 times

And both have 2 fire buttons that work with Atari's. It makes me wonder if they act as capacitors in some way that the different joystick circuit of the CPC sees as a connection, but isn't detected on other machines.

I did just find a stick I forgot about at the bottom of my quick use storage, so will go and try that too.

[rubber_jonnie]

Ok, weird.

The joystick I just found is branded 'Discwasher' and isn't really much more than an upmarket 3rd party Atari CX40 stick, and uses the same clicky domes as the other Atari sticks.

Only it doesn't exhibit the same behaviour and works just fine. Go figure...