[Coco] CoCo 2 bitbanger does 57600bps!

[Frank Pittel]

I hope this success means that I have a volunteer to write a simple
program that runs on linux that can listen to a serial port and save
everything that it recieves into a file for later inspection or printing!! :-)
Of course the best solution would be for Boisy's drivewire handle the chore.
This way I could print while drivewire is active. :-) :-)

In my case there's no hurry since all my Coco gear is packed away waiting for
me to finish up a couple of other more pressing projects. I may have to add
the writing of the software to the list of things to get to one of these days. :-(

Frank


On Thu, Mar 23, 2006 at 08:34:51PM -0600, Roger Taylor wrote:
> At 07:34 PM 3/23/2006, you wrote:
> >Roger,
> >Congratulations on your achievement.  Just to clarify, you're
> >rounding the clock rate up in your message right?  I take it that you
> >really mean .895 MHz and that you didn't alter the CoCo's actual
> >clock speed.
> 
> No mods at all, Boisy.  When I say "1mhz" I mean .895, or the standard 
> speed.
> 
> 
> >When I developed DriveWire, I experimented with 57600 bps on a CoCo
> >2.  Receiving worked with inlined, straight run code, but I found it
> >to be flakey when tested with different PCs and operating systems.
> >At those higher speeds, it appeared that some serial ports had
> >slightly different tolerances, and the bit transition timing was hit
> >and miss.  As you know, it's all in (1) how consistently in time the
> >CoCo samples the bit and (2) where the CoCo starts sampling the bit.
> 
> Yes, the timing is so precise that it took me a week to nail it down.  I 
> plan to test more under Windows XP on two computers and Red Hat Linux 9, 
> but that's all I have.  Right now I've got the sending computer in a loop 
> and the CoCo hasn't missed a character.
> 
> >Yes, the PIA on the CoCo 3 can be pushed to 115200 bps as the sender,
> >but I had a much harder time getting the CoCo 3 to run at 115200 as a
> >receiver.  As I recall, the timing was close but not quite enough to
> >detect the start bit with consistency, and I must have tried half a
> >dozen permutations of instructions to accomplish the feat.  With a
> >6309 in native mode it could be achieved, but I wanted a solution
> >that would work with the baseline 6809 running at 1.78MHz.
> >At any rate, it was a great learning process for me, and out of it
> >came a very successful product.  I'm sure you're having fun
> >discovering all of this yourself!
> 
> Only a true programmer would call this fun... and it is!  :)
> 
> As for doing 115.2Kbps on a CoCo 3 or any CoCo (that can switch into 2mhz 
> mode) with a 68B21 for that matter, only a test will prove it.  I haven't 
> gotten that far, but when I do I'll be sure to post the news.
> 
> One thing's for sure... all those messages over the years saying that the 
> CoCo can really only do 1200bps over the bitbanger port needs to be 
> squashed for good.  Even the 9600bps limitation comments are ridiculous.  :)
> 
> 
> 
> 
> Roger Taylor
> 
> 
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