I've designed a new circuit for controlling MSSIAH, Cynthcart, and other C64 software using potentiometers.
This circuit features sub-miniature trim-pots for calibrating the range of the knobs' rotations. No longer are dead-zones a problem when using pot control - this new circuit allows the full range of the pots to be utilised. The controls may be calibrated using MSSIAH's Diagnostics page, and once set, can be left alone.
I have also fixed the issue of pot tapering. This is the effect of the pots moving the on-screen pointers at different speeds, depending on how far the knobs are turned. This new circuit has a reverse logarithmic behaviour that approximates how the C64 operates closely.
Note that the circuit must be doubled to allow four pots to be used, with two pots on each of the Commodore 64 joystick ports.
I have constructed the circuit, twice, on a piece of stripboard measuring 2"x2". The mod may be housed inside a C64 along with case-mounted pots, or, as I have done, in an external controller box which connects to the joystick ports. All the parts are standard and can be obtained cheaply.
VR1 and VR2 are the main pots, while VR3 and VR4 are the respective trim-pots for calibration.
I would very much like C64 users to try this out. If you decide to assemble this new improved circuit, please post your results here. Thanks.
Oh, and it works with Cynthcart, Prophet64 and any other C64 software which uses pot/paddle control.
Last edited by InactiveX (July 6, 2011 4:44 pm)