From: Marko Mäkelä (msmakela_at_gmail.com)
Date: 2007-05-09 08:19:07
On Wed, May 09, 2007 at 02:33:11PM +1000, Daniel O'Shea wrote: > I was wondering, in both Jim and Levente's microcontroller to joystick > port projects - is interfacing a microcontroller's digital output > (high/low) to the joystick input likely to cause the same issues with > the CIA chip as noted here: > > http://www.floodgap.com/retrobits/ckb/display.cgi?26 The reported issue was that Sega gamepads pull lines high or low, while joysticks are open-collector outputs that pull lines low or leave them floating. Yes, you will have to be careful with this. In Atmel's AVR microcontollers, you can get an open-collector active-low output by initializing PORT=0 (which it is by default after a reset) and controlling DDR. When DDR=0 (the default after a reset), the output driver is inactive (or the line is an input). When DDR=1, the output driver is active, and it would be pulling the line low. Marko Message was sent through the cbm-hackers mailing list
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