2 Feb
2012
2 Feb
'12
12:31 p.m.
On Feb 1, 2012, at 9:04 PM, Jim Brain wrote:
Yes, but I was wondering if there was an even less
involved solution. On the 64, the decoded IO at the user port makes this a trivial task,
and I'm not sure if the AppleII has a serial card or not.
I'm gonna go with everyone else and say your quick and dirty solution is to use the
joystick port as GPIO. There are 4 annunciator pins you can use as #CS, SCK and MOSI, and
use a button input as MISO.
As far as designing your own board, it's just a damned shift register, so I assume
you're using a '164/'166 combo for shift in/shift out (or a universal with
parallel load/out) and simple counters for word length/baud generation (assuming
you're not just using 1MHz for SCK). You shouldn't need more than about 5 chips
to make a really simple SPI board, not counting any level translation.
- Dave