[simpits-tech] Small CRTs (Was: Just a quick update.........)

[dabigboy at cox.net]

---- Gene Buckle <geneb at deltasoft.com> wrote: 
> 
> This is for the EPIC input matrix, but it would be essentially the same 
> schematic for hacking a keyboard matrix.  Once you identify the row & 
> column lines it's easy.

I've actually done something similar for the "little" Leo Bodnar board to get 30+ inputs out of the 12 pin model, but the rows and columns are of course clearly documented. I "decoded" my PS/2 encoder last night. It has one small connector of pins (8 of them) and one large connector....I've made the assumption that these corresponded to rows and columns. After documenting most of the keyboard inputs, I started organizing them in a spreadsheet. Now it's entirely possible I've misidentified which pins should be considered part of a row and which ones are part of a column, but I reached a point where a few of the inputs I documented would conflict with other assignments if I were to wire them up to the CDU.

In other words, both connections of a few of the inputs I documented occurred entirely within a row or column. But I did get enough combinations documented to handle all the buttons on the CDU except 3 (I will sacrifice "ON/OFF", "BRT", and "DIM").

The main problem is that the CDU itself uses a matrix, and it's not much similar to the keyboard. Even with diodes, it appears I would at some point activate more than one input with a single button press (with the conflict occurring on the CDU sidel). The situation is no doubt complicated by the fact that I don't have docs for either the CDU or the keyboard, so both matrices are just the best I could figure out and may not be exactly right....I have a sneaky suspicion that if I fully wrapped my head around the CDU's keypad matrix, life would be easier.

> Alternately, you could just grab an Arduino and a Centipede Shield and 
> skip the whole keyboard mess to begin with. :)

True that....the Centipede is on my to-buy list, and I've got your output board for the Centipede downloaded in case I decide to have one made for myself. :)

Matt