Prototype v0.1

A project log for HACKACALC

Under this project I will document a process of converting cheap scientific calculator into cool programmable one :)

SHAOS 11/15/2017 at 05:140 Comments

I was thinking for so long how I should make my 1st prototype - on breadboard, as wire-wrap assembly or dead-bug style soldering, but finally I've decided to go with PCB (will order through OSHPark as usual) designed in Eagle v5 (version that I have standard license for). So main part of the prototype is 7 analog switches 8:1 (CD4051) and one decoder 3->8 (74HC138):

Switches implement keyboard matrix 7x8. Also you can see here 2K ROM that will store "program". Additional circuitry is address counter (I'm not so sure that it will work right away):

And this is manually routed PCB 18x10cm that I will order tomorrow:

Circuit doesn't have clock generator on board because I didn't decide yet how to do that - most likely here it will be manual step button (with RS-trigger) on prototyping area at the bottom. Will see how it goes...

UPDATE: Ordered on Nov-16 through OSHPark: