[Coco] RS232 Pak needed

[Steve Bjork]

Picaxe are great for a quick and dirty test or small production of 
something.  But making a project with orders of 50 or more, I would use 
a pic or some other micro-controller with a lower cost than the Picaxe's 
$3.50.  (more like $0.75 each)

My first step is take a look at what you are trying to interface into 
the CoCo.  If we are looking at just older RS-232 device then making a 
replacement for the old RS-232 Pak is the direction we should go.  The 
cost of goods to build this type of board would run under $7.50.   The 
"hard" part of doing this project is writing the code to make the Pic 
chip think that its a 6551.  One option that we could add would be a 
large I/O buffer with full hardware handshaking.  That could speed up 
the I/O.

Steve


On 9/19/2013 11:21 PM, Gene Heskett wrote:
> On Friday 20 September 2013 01:26:01 Steve Bjork did opine:
>
> 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
>
>