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Old 15 August 2019, 13:36   #7
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Join Date: May 2009
Location: UK
Posts: 92
Thanks. 10k was my first thought. I'll change it if I get any weirdness.

I've got small (200R-600R maybe) protection resistors leading into and out of my MCU on the data lines since I don't really trust the Amiga all that much. Pin 6 being used for both Atari-style Fire1 output-to-Amiga and an active-low SPI-frame input-from-Amiga signal depending on Pin 5 made me nervous, and I didn't want a bad scenario where both the MCU and Amiga would drive the line together unprotected. (Too cheap/lazy/cowboy to use the two inverting buffers that the real CD32 pad uses.)

Plus, I'm intending this to be used with older software, and I've got some configuration (maybe software/maybe hardware) that'll let me map Square or Triangle on the PS2 pad to Jump on A500. It's entirely possible that some weird/old software will do something unexpected with those POT-X/Y pins, so I'm very keen on protection there.

I had a look at the Amiga's schematics near the joystick port and did some voltage divider calculations and came up with a scenario where either the MCU or the Amiga wouldn't be able to pull the signal down to something like 0.25V with a 10k, so that's where 20k came from.
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