[Coco] CoCo 2 bitbanger does 57600bps!
fwp at deepthought.com
Fri Mar 24 12:30:34 EST 2006
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. :-(
On Thu, Mar 23, 2006 at 08:34:51PM -0600, Roger Taylor wrote:
> At 07:34 PM 3/23/2006, you wrote:
> >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
> >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
> Coco mailing list
> Coco at maltedmedia.com
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