Logic PCB Business Card
I’ve seen PCB business cards for a few years now on Hackaday, and I figured it was time to design one of my own. Most PCB business cards involve a microcontroller. I wanted to do something a bit different, so my card performs its intended function strictly with digital logic gate and D-type flip-flop (DFF) ICs.
The card implements a digital finite-state machine which displays the next character of my last name on a 7-segment display each time the button is pressed. Luckily all 11 characters in my name can be reasonably shown, essentially spelling out FLoyd-JonES. I simulated the design in Altera’s Quartus II FPGA software before constructing it in Eagle.Onboard is a 4-bit counter comprised of DFFs in which the output of one DFF is fed into the clock input of the next, and the inverted output of each DFF is connected to its own input. The clock input to the first DFF in the chain is connected to the button, which is debounced by a parallel capacitor.This logic is very difficult to think about until you actually map it out on paper and prove it to yourself. It’s obviously weird to be using the clock inputs in this manner, but it saves gates and this thing needs to operate on the order of Hz, not MHz.
For more detail: Logic PCB Business Card