hamster Posted September 4, 2014 Report Share Posted September 4, 2014 Here's how to read a pot, using only two resistors and a capacitor: http://hamsterworks.co.nz/mediawiki/index.php/Cheap_Analogue_Input It is based around the technique used for the joystick interface on the Apple II. Only downside is that you need to calibrate the the limits - but perfect as a paddle interface for a game of Pong, where you could just remember the max & min readings. Link to comment Share on other sites More sharing options...
johnbeetem Posted September 6, 2014 Report Share Posted September 6, 2014 Cute! I've done this using a 555 timer, which I notice is how The Woz did it (in his case with a 558 quad timer). I think you get better stability with a 555 rather than depending on the FPGA's input threshold voltage. You can get a low-voltage 555 these days, or use a 74VHC123A dual one-shot. If you really want to avoid external chips, you might get better results with a precision FPGA input standard that uses a Vref pin or use differential inputs comparing to a common Vref. Link to comment Share on other sites More sharing options...
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