At 03:08 PM 11/11/97 -0500, kotay@ahwanee.cs.dartmouth.edu wrote:

>As I wrote the stuff below I realized that the biggest
>decision you have to make is whether to design this
>product to interface to microprocessors or to
>computers.  If you design for microprocessors, some
>type of synchronous serial protocol is better and I
>would probably send the data in binary.  If you
>design for computers, an async serial protocol would
>be better and I would send the data in ASCII.

By breaking out the Communications Unit from the Ranging Unit, I should be able
 to accommodate either one.

>>   -  Data format for measurement data returned

>I would suggest millimeters.

I suppose this would have to vary depending on the range being measured.

>>   -  I2C, SPI, or none of the above

>RS-485?  People may want to connect this to a PC which
>is why I might favor an async serial method.  It's
>easy to make an RS-232 to RS-485 converter and RS-485
>allows up to 32 nodes on a single twisted pair.

I was thinking it would make sense to leave the output at TTL levels, and allow
 the end user to interface this to whatever physical medium was appropriate for
 their application.

>>   -  Baud rate/clocking (async 9600/4800/2400/1200? Autobaud? Sync?)

>Async 9600.  You shouldn't need anything faster than that.

Agreed.... Not much data to send, so 9600 is overkill.  However, it's also
 fairly "standard", so it's probably a good choice.

>>   -  Distribution mechanism
>>        PIC code/Schematics/PCB layout on web for download?
>>        Preprogrammed PICs and etched PCBs for purchase?

>Both if possible.

Agreed.  Right now I am leaning towards a standardized circuit and PCB, with
 different versions of the Ranging Unit (RU) and Communications Unit (CU) PIC
 code on a web site for download.  This way, we could pool resources to have a
 batch of PCBs made up by a board fabrication house, and allow individuals to
 program their own PICs.  I would also be willing to program PICs based on the
 user's choice of the to-be-determined "standard" RU and CU designs.

 - Rick "I love it when a plan comes together" Dickinson

+--------------------------------+------------------------------+
| Rick "The Notes Guy" Dickinson | Views expressed by the author|
| Lotus Notes & Domino Solutions | are not necessarily those of |
| (818)563-1061 rtd@notesguy.com | Enterprise ArchiTechs.  They |
|   http://www.eArchiTechs.com   | might not even be mine....   |
+--------------------------------+------------------------------+