[ColorForth] Why I'm Here

["Arthur W. Green" <goshawk@xxxxxxx>]

Mr. Ivie wrote:
> That's a fairly large assumption. If by "standard" serial device you mean
> a normal, garden-variety RS-232 thingie, the USB port is the wrong place to
> put it.
> 
> RS-232 is designed to deal with single-ended signals ranging from +-3V to 
> +-15V. This is radically different from the differential signals with at 
> least a 200mV difference used by USB. It's going to take some sort of
> circuitry to paste the two together, and I suspect that would be better
> spent on a UART for the machine you're trying to use than pulling your
> hair out over USB.
> 
I know someone who had offered to build me such a device as a favour to me.

> There are products in the Mac marketplace to convert USB to
> RS-232. There are plenty of hits over at http://www.macmall.com/ if
> you search for "usb serial". Bear in mind that such devices are USB
> devices, so you have to speak via whatever USB class profile they
> use.
> 
That would unfortunately defeat the purpose of what I had in mind.

> 
> I do not believe so. The whole point of the USB controller is to do a
> lot of the USB housekeeping for the CPU. There's an awful lot of
> intelligence sitting between you and the USB wires; I don't think you
> can get directly at the wires.
> 
That's what I figured. :P

> 
> Tell us more about the motherboard you're using. Most motherboards I've
> seen have serial ports on them. Failing that, there's usually a parallel
> port; that would be much easier to interface a serial device to (you'd
> have to implement a software UART and have some level translation 
> circuitry out there...).
>
My motherboard has parallel ports and serial ports, but I was less than pleased
with the timing on many serial ports and my parallel port is already occupied.

I guess in an overly optimistic kind of way, I had hoped maybe I wouldn't have
to waste the USB connections on my motherboard. 

Sure, I could setup USB support, but we're back again to the issues I have with
USB.

Thanks again for your time.

Best regards,
-- Art
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