In my previous blog entry I documented my approach to designing and principles of use for a Hexadecimal keypad to interface to my 6502 CPU based computer. One modification to reduce the chip count, I changed my original circuit and replaced the Hex inverter IC (4069), with a single MOSFET transistor acting as a simple inverter.
Now I have combined and built the keypad with an LCD 20 x 4 digit display into a complete module.
The keypad outputs (8-bit ASCII with 'strobe' line) and connects to Port B of the 6821 PIA. The 'strobe' line connects to CB1 input and triggers /IRQs whenever a key is pressed.
Serial ASCII from the 6521 ACIA at 9600bps connects to the Adafruit Serial - LCD display interface, with serial data appearing on the LCD.
Pictures showing the unit; standalone and wired to my 6502 CPU computer, a few 'flying wires' but it's just in testing phase at the moment.
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| Completed unit |
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| Monitor listing with prompt |
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| Wired to the main CPU computer - testing configuration |
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| Entering the 'L' (List) command |
Amazing work. I love the modular design and veroboard choice for prototyping. I wish I started my project like that instead of euroconnectors and low quality IDE male connectors as my expansion cards sockets, however it looked cool to me at the time :-)
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