liam . <piclist@mit.edu> wrote:

> I'm trying to workout how to approach the design of a Bike Computer.
> This is not a computer for a bicycle but rather for an exercise bike
> that will interface with a real computer. 
> 
> The exercise bike already is fitted with a reed switch and so a sense
> of wheel rotation is known. I'm of split opinions at the moment however
> at the moment on whether to use a PIC onboard to work out stats like
> speed, distance, RPM etc and then send this to the computer or to only
> send the wheel telemetry to the computer and use software on the
> computer for processing. How would others do it ?

    Liam:

    Do as much processing as possible on the computer; have the PIC do
    as little as possible.

> The concept has been suggested that multiple bikes are connected to the
> same computer for telemetry recording which also would influence the
> decission of where to process and how to connect.

    I'd do it the same way regardless of the number of bikes connected. 

> The obvious solution for connection was RS232 however most laptops dont
> have serial anymore so then its a case of embedded USB support or use
> USB dongles. Which would be better ??

    Your application -- an indeterminate (possibly quite large) number of
    devices that need to be individually identified and accessed, and
    possibly hot-attached and -detached -- is perfect for USB.  RS-232
    is terrible for that sort of thing; if you used RS-232, you'd have to
    invent your own protocol for doing all the things that USB does
    automatically. 

    Personally, I'd use USB microcontrollers instead of USB-to-serial
    dongles... But if you're already comfortable writing PC apps for
    RS-232 communications and have no experience writing USB apps (and
    no desire/time to learn), then I guess serial-to-USB dongles would be
    ok.  They'll be more expensive, though, and more cumbersome than
    straight USB devices, and your customer may have to install a driver
    on his PC. 

> This is a very low budget project and I wanted to be able to get this
> working with a minimal of components in a short time.

    No big surprise there...

> I tried searching google for someone else's attempts at a similar
> project however I didnt find any. If anyone knows of any, please let
> me know.

    You may want to look at Jan Axelson's book, "USB Complete".  She
    doesn't discuss applications exactly like yours, but she does show
    how to transfer data back and forth over USB using low-cost
    microcontrollers and the HID driver that's built into every modern
    operating system. 

    Information on the book (and source code, and lots of other USB
    info) is available on Jan's web site, at http://www.lvr.com .

    Good luck...

    -Andy

=== Andrew Warren - fastfwd@ix.netcom.com

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