Cassie Keyboard Prototype Interface Box
This interface box is an adapter which allows the Cassie keyboard to be used with a Mac 128k - Plus.
Here's a rather poor schematic of the board.
provided some additional notes:
- I know nothing about this device, but looking at the schematic, I can guarantee you [U1] is some type of microcontroller. I can figure this out from a few things on the schematic.
- Crystal oscillator X1 and the two capacitors (although only C1 is labelled). This is an oscillator tank circuit that is very common.
- If it really was an eprom, the unused address lines would not be left floating -- they would need to be pulled high or low. as it is, I'm sure it is just extra I/O port pins from the microcontroller.
- The thing labelled "C3" isn't a resistor, as shown on the schematic. I believe it is a diode. This is to protect the processor in case somebody applies power backwards on the device somehow.
- The wire that connects to the C3/C2/C1/J1/J2/U1 is undoubtedly the ground (0 V) wire.
- The wire that goes to the other side of "C3"/J2/U1 is the power, probably 5V.