[Coco] RS232 Pak needed

[Gene Heskett]

On Friday 20 September 2013 08:09:51 Louis Ciotti did opine:

> Wouldn't it be better to just implement a 6551 in a CPLD or FPGA,
> keeping it backward compatible with older software, and maybe
> implementing improvements/other options accessible via the control
> register.

I don't think that is an advantage, Louis.  The 6551, with its broken 
hardware flow controls, is a very poor chip to emulate because its a broken 
chip.  Throw in the cost of joining the "club" and buying a development 
board just to play on would be an upfront cost that would put the kibosh on 
even getting started.

> 
> On Fri, Sep 20, 2013 at 4:07 AM, Steve Bjork <6809er at srbsoftware.com> 
wrote:
> > 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
> > 
> > --
> > 
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> 
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Cheers, Gene
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