the DE1 joystick adapter

[vanfanel]

Hello there

Now it's happy time since the DE1 is becoming my new Amiga!

I've been thinking about adding a joystick port to my Altera DE1, following tobiflexx's schematics. But I just need ONE joystick, so I don't see the need to make the full circuit.

If I just make

DB9 GPIO

1---------------39
2---------------37
3---------------35
4---------------33
5---------------31
6---------------40
7---------------11
8---------------30,12
9---------------34

without further complications (no resistances, no more connections, etc...)
shouln't it work??

thanks!!

[Talus]

Be careful. Pin 11 on the 40-pin header on the DE1-board is connnected to 5 volts and that will damage the FPGA if it ever gets routed back into it through the joystick. I would suggest you avoid soldering the connection between pin 7 on the joystick and pin 11 on the header. "Dumb" C64/Amiga joysticks don't need it.

You will also need to enable pull-up resistors for the inputs in the UCF file. If the FPGA doesn't have internal pull-ups (don't know Altera devices), then you will need to solder external resistors.

This simplified interface won't work for mice or fancy joysticks with auto-fire (they need 5V to feed the logic and then you will need those external resistors), but it should be good enough for, say, an old Wico stick ;)

[tcdev]

Be careful. Pin 11 on the 40-pin header on the DE1-board is connnected to 5 volts and that will damage the FPGA if it ever gets routed back into it through the joystick. I would suggest you avoid soldering the connection between pin 7 on the joystick and pin 11 on the header. "Dumb" C64/Amiga joysticks don't need it.
Seconded. You should only need GND and the switches.

Interestingly, the DE2 has clamp diodes protecting the GPIO connectors, whilst the DE1 doesn't.

You will also need to enable pull-up resistors for the inputs in the UCF file. If the FPGA doesn't have internal pull-ups (don't know Altera devices), then you will need to solder external resistors.
Altera devices have weak (22k) internal pull-ups which need to be enabled in the constraints (QSF) file.