From: Scott McDonnell (NetSamurai_at_comcast.net)
Date: 2004-10-23 01:02:39
----- Original Message ----- From: "Jim Brain" <firstname.lastname@example.org> To: <email@example.com> Sent: Friday, October 22, 2004 5:12 PM Subject: Re: Commodore joystick ports > Scott McDonnell wrote: > > >Jim, > > > >As Hársfalvi mentioned, it is current that needs to be generated, not > >voltage. A resistor creates a voltage drop across it, which is a function of > >current. (Resistance=Current/Voltage) The voltage is 5V, the resitance is a > >range that you know from the potentiometer values, you simply need to create > >the corresponding current to emulate the resistance you need. > > > > > The nitpicker in me always thought it was V=IR, so R=V/I... You are correct. I was having a mild flatuation of the brain... :) > > I looked at a resistor ladder DAC, but I don't have 16 IO pins to spare > (8 per POT), and the board real estate for 2 ladder DACs puts me way > over the .625x.625" pcb space I have to work with. (On a related note, > anyone have a source for a bit larger DE9 shells?) > > >in 256 different currents at each axis input. Probably way more resolution > >than a commodore mouse provides. > > > > > Oh, I don't know.. If someone wanted to re-use this as a 1351 mouse > emulator, they'd need either a stable 7 bit resolution (1351 discards > low bit due to timing issues), or 8 bit resolution. > > I'd travel down the path, but as of last night, the idea used by the > 1351 designers and Hársfalvi noted in his project is working pretty > well. I can get from 10 to 255 on the POT lines using 2 10K resistors, > configured as noted in his PIC mouse project plans, and the jitter is < > +-3 (I cleaned up my code to reduce execution times), and only uses 3 > pins on the AVR (INT1 and 2 data pins). Ok. Sounds like you got it working satisfactorily. : ) Just thought I would pipe in and offer my own suggestions. Hope I was at least some help. Scott Message was sent through the cbm-hackers mailing list
Archive generated by hypermail pre-2.1.8.