Looking to build simple home computer.

[Chris Green]

Hi,

Its been a long time since I designed/built any HW projects (I became
a SW Engineer!) so apologies if this is the wrong group.

I was thinking about building a simple single-board computer that
could display graphics on a TV and was wondering what sort of
components would be most suitable these days for use by a hobbyist.

A basic design would be a CPU with some external memory. Part of the
memory will act as a frame buffer thus some logic will be needed to
read colour values out and pass them to a DAC acting as an input to a
video encoder (I was thinking possibly an AD724 RGB to NTSC/PAL
encoder?).

Some (rough) specs:

16-bit CPU, clock speed around 10-20MHz.
128K-512K RAM
Video display ~ 256 x 256 colour (555 RGB?)

Can anyone recommend suitable components I should be looking at using?
I was hoping to use a 68000 for the CPU since I'm familiar with
programming it and seem to remember it being pretty simple to design
HW around. However it has been a long time and from searches I have
done I can't find a retail supplier who stocks these any more (I live
in the UK).

Thanks for any help,
Chris.

 

[Miguel A]

Hi Chris,

Check the Internet for projects with PIC microcontrolers.
I Know there are some simple projects around that use PICs for
implementing a game in a B&W TV. Start by gathering some information
on modern microcontrolers... 68K CPU is a bit old for modern
projects

regards,

Miguel

 

[Michael Black]

Hi Chris,

Check the Internet for projects with PIC microcontrolers.
I Know there are some simple projects around that use PICs for
implementing a game in a B&W TV. Start by gathering some information
on modern microcontrolers... 68K CPU is a bit old for modern
projects

regards,

Miguel

But if someone is just building something for their own use, what
difference does it make how old the CPU is? The only relevant factor
is whether one can get one. So, it would be fairly stupid to pick
an 8008 at this date (well, it would have been fairly stupid after
the 8080 came along) because they were never common, and date back
thirty years. Post-8080 CPUs usually did see common useage, so
they should be easy to get ahold of. There are exceptions; I wouldn't
bother with the Fairchild F8, but then it wasn't a good choice a quarter
century ago.

If he's familiar with the 68000, then that makes it a better choice
than starting from scratch with a more recent CPU. And even if he
didn't know the CPU, it dates from a time when it was used in hobby circles,
so there is material out there for it.

Michael

 

[Rob]

Hello Chris,
I would probably be able to help here. This is the sort of project
that I did with my brother years back. He also went into programming.
But a programmer and a hardware engineer make a good combination,
ingeting something like this going.
Regards
Robert (Bucks, UK)