Well that's just odd:
Key C1 C2 C3 C4
0 1 1 0 0
1 0 0 0 1
2 0 0 1 0
3 1 0 0 1
4 1 1 1 0
5 0 1 1 0
6 1 0 0 0
7 0 0 1 1
8 0 1 1 1
9 0 1 0 0
* 0 1 0 1
# 1 0 1 0
...I thought to myself: "If the Coleco pad uses a cr_p ton of diodes to encode the keypad maybe if I used a 4-bit encoder to do the job I could free up some board space for other functions?"
I kind-of expected the encoding would be in binary as that would be logical, but it isn't. Ok, maybe the encoding is set up to minimise key-ghosting, but I don't see it...
...anyone got any idea why Coleco went for this arrangement? I don't actually know but I presume the console toggles Pin 5 on the joystick and reads the direction lines for the keypad in software when it's appropriate to do so, so any arrangement could have been valid.
Not a biggie, just if I try this the 'lack of logical arrangement' will make it more likely I make a mistake.
Out of curiosity is anyone in touch with the Colecovision, and ADAM, designer(s)? From my limited understanding so far on the one hand it's a beautifully designed system, but on the other hand it's full of design choices I just don't get at all...
...I always assumed the ADAM's funkiness is a consequence of the design team showing marketing an engineering prototype that then got pushed out of the door instead of waiting for the production version. But that doesn't explain the (to me) more baffling choices that had to be in place from the moment pen was set to paper.
I always found listening to the likes of Bill Herd (Commodore) talking about such things both enlightening and entertaining... I'd love to hear from the Colecovision / ADAM's creators.
Edited by CharlesMouse, Thu Apr 11, 2019 10:23 AM.