[Coco] RS232 Pak needed

[Gene Heskett]

On Friday 20 September 2013 01:26:01 Steve Bjork did opine:

> The Max-232 is only the level drivers for changing TTL to RS-232 levels
> and back.  (Not the logic chip for doing serial i/o.)
> 
> As for getting an UART chips, it's cheaper using an PIC, Picaxe or some
> other modern Micro-controller to do the serial i/o work.
> 
> With the Picaxe, I can get baud rates about 4 times faster using $3.50
> part.  Why spend $30+ for an outdated (by 30 years) chip?

I am with you 100% Steve.  There is so darned much breakage in the 6551 
that we have tried to write code around for 30 years now, without anyone 
doing anything to rectify the fact that it has more bugs than a 10 day old 
carcass alongside the road.  That chip should have been binned the instant 
a better one came along.  IMO the 16550 is not it as it ties up 16 IO 
addresses to properly handle it, so thats a no go from the gitgo

With the pikaxe running from its own teeny little os in flash, all we'll 
need to see are the 4 data & configuration port registers so it looks most 
like the 6551 but actually has working flow controls.  With a 2nd, 4 
address wide port into its flashrom, even that could be updated by the 
coco.

But I'd put a flea clip onboard write disable on that in case the coco did 
a confetti screen too.

If you can send me the eagle files to build this serial port function, 
preferably 2 or 3 up on one card, while staying inside the 4 address limit 
for most coco i/o per instance per port, I will make the first 2 cards on 
my milling machine.  If it works, the eagle files goto somebody in Hong 
Kong for enough copy's to fill the needs at 1/8 the cost for me to actually 
produce them in gty's.

Two gotchas for those 1st cards. (1 for you, 1 for me to be used as test 
mules)

I cannot do plated through holes, so tsop packages would at least solve 
that dip chip problem.  Any other thru via's needed, a bit of wire will 
make these breadboard, proof of concept cards work.  If someone can do the 
eagle files, I can do the rest, ready for part soldering. I have done 
simple stuff (like the spindle encoder in my cnc lathe) in eagle but a 
younger mind than my rusty wet ram will probably do it faster for the more 
complex layouts.  It will be 79 the next time the date string says the 4th 
of the month. Stuff like this "keeps me out of the bars". :-)

Forget the DB25 connectors, the 7 wire protocol thru a db9 connector has 
been the default method for 20 years now, and saves acres of board space.

As evidenced on this list, there IS a market for rs-232 port cartridges.  
But one per "pack" is never enough.  If the 2nd one isn't going to be used 
as a serial mouse port, which fixes the spastic mouse with one that puts 
the click exactly where the pointer is, then it could be made into a midi 
port, so the baud rate register should include 31250.  I have done both at 
various times, currently using the 2nd port for a mouse, a full 3 button 
mouse.

What say you, Steve?

Cheers, Gene
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