[Coco] Smart IO interfacing on the CoCo

[RETRO Innovations]

On 4/25/2020 12:35 PM, Gene Heskett wrote:
> The real question, Jim, is: If you proto a design and it works well, will
> it still be available a year from now for a 3rd run of 50?  Lots of this
> stuff gets replaced by newer, glossier versions everytime you load the
> washing machine with last weeks underwear.  We have, or did have, 5 year
> laws, but they seem to be routinely ignored.  Have they been sunsetted?
> IDK.

I think your comment is more directed to Allen, but I will say that I 
designed a unit with an AVR8 based ATMEGA1281 in 2004 and I am still 
able to source those parts new from Microchip (who bought Atmel a few 
years back) without a "Last Time Buy" commitment.  I think PIC has been 
reasonably good as well, at least for the PIC14/16/18 line, not sure 
about the 24/32 lines. That said, I've had to redesign the same unit 
because it's a CoCoSDC-like drive for another platform, and 3M (who made 
the SD connector) EOLed it.  At that point, I looked at all the 
suppliers and noticed many of them designed a specific variation of SD 
card connector (it has a half moon indent in the top metal), so I 
redesigned with that part in mind.  Finding those has been much easier 
(and cheaper). So, I agree parts EOL is a major concern.

My main concern with such USB projects is the cost.  As a general rule, 
I set sale prices as 3X COGS (cost of goods sold) which is pretty 
standard.  I lump in PCBA service costs, shipping, parts, PCB 
manufacturing, taxes, etc.  If a part costs $10.00 to source, that 
immediately means the sale price of the finished product will be 
$30.00.  Then, I think about the value of that as a potential buyer.  
$30.00 for just the module is tough to swallow.

Mind you, I know USB support is possible (Paul Fiscarelli's done it, I 
think Mark Marlette had USB going, I remember seeing some project at a 
recent CoCoFEST! doing USB, etc.), so I wouldn't pooh pooh the 
possibility of it, just the economics.  I actually chose the PIC 24MX 
line because it also offers USB host mode and is very cheap ($2.00 or 
something at the @100 unit quantities I order), but I've not got the 
project moved along in light of other fun things.