Allen Huffman alsplace at pobox.com
Mon Mar 6 11:09:35 EST 2017

> On Mar 6, 2017, at 10:03 AM, camillus gmail <camillus.b.58 at gmail.com> wrote:
> I was wondering, if a single 6809 or 6309 can handle USB protocol. If this could be done then a second cpu would be easy to imply in the exsisting coco's., and act as a dedicated USB controller ( does not have to be a 6809 but like to stay in the era )
> ...

> I don't know I'm just a thinker...LOL
> But it would be not the first time someone made a big invention from someone else s idea's  ...lol

It's a timing issue, I believe. USB is just a serial stream and a protocol on it. The Arduino can handle USB for keyboards with just a few wires from it's digital pins to a USB connector, but not the stock Arduino. You have to swap out the timing crystal. You can buy a "$5 Arduino kit" where you wire up some parts to a breadboard and have an Arduino, including the timing crystal, so such a board could be wired for next to nothing and do USB keyboards with open source software.

BUT, I believe (from foggy memories of researching this a few years ago), the timing was faster than what our 6809 could handle.

You will notice many Pi projects chain an Arduino to them for doing fast I/O, since while the ARM chip on the Pi is very fast, the OS layer is not realtime. Many projects put an Arduino polling pins for reading I/O (joysticks, etc.) and then spit that back to the Pi as a USB Serial stream.

		-- A

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