Hobby Electronics Basics PIC's and USB

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Subject Author Date
PIC's and USB Randy Day 08-30-08
`--> Re: PIC's and USB Paul E. Schoen08-30-08
Posted by Randy Day on August 30, 2008, 8:21 pm
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I downloaded some stuff on how to use
USB from:

http://pe.ece.olin.edu/ece/projects.html

I want to make a PIC act as an HID
keyboard, but I've come up with a couple
questions before I get too deep into this.

1) Most of the schematics I see show an
external xtal running the clock; is this
necessary. or is the onboard clock
adequate for short data xfers?

2) Prof. Minch's code simply keeps sending
the same text over and over. What's the
simplest way to have the computer send a
char to the PIC saying 'OK, send me the
next batch!'.

Thanks. This stuff is like trying to
swallow an elephant!

Posted by Paul E. Schoen on August 30, 2008, 10:38 pm
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>I downloaded some stuff on how to use
> USB from:
>
> http://pe.ece.olin.edu/ece/projects.html
>
> I want to make a PIC act as an HID
> keyboard, but I've come up with a couple
> questions before I get too deep into this.
>
> 1) Most of the schematics I see show an
> external xtal running the clock; is this
> necessary. or is the onboard clock
> adequate for short data xfers?

USB clocks need to be very accurate, so the external crystals are the way
to go.

> 2) Prof. Minch's code simply keeps sending
> the same text over and over. What's the
> simplest way to have the computer send a
> char to the PIC saying 'OK, send me the
> next batch!'.
>
> Thanks. This stuff is like trying to
> swallow an elephant!

I got a USB development kit from Microchip that can be configured as a
keyboard, mouse, game port, or a USB to Serial converter. They have pretty
good tutorials, but I attended an introductory class on USB when I went to
their MASTERs conference a few years ago, and then I went to another local
full-day training class that helped me understand a bit more.

The microchip forums are also good resources for USB questions, if you are
using Microchip products such as the PIC18F4550.

You might check the Microchip website for a training class in USB From
Scratch (390 USB). There are some coming up soon in Cleveland, Boston, and
LA.

Another good USB resource is www.beyondlogic.org.


Paul



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PIC's and USB August 30, 2008, 8:21 pm