>> but then he should realise that using the PIC as USB slave 
>> will eat a
>> lot of resources (CPU, flash, RAM).

> Resources yes but if you are using a PIC you need to 
> implement the serial
> routines anyways so you need some flash for that, so if you 
> have 3 K of
> spare flash (10% on a 18f2550) and a few cycles to spare   
> it's clearly
> cheaper (imho) to utilize a PIC vs an FT232RL. I guess the 
> Serial routines
> could take up at least 300-500 bytes? so incrementally you 
> are only looking
> at 2.5 K

I don't think USB will be just 'a few cycles', and 300-500 seems a 'bit'
large for asynch routines.

> As for RAM sure if you do not have the additional 80-120 
> bytes needed you
> are better off with the FTDI solution, but at $ 3.00 to $ 
> 4.00 that's an
> additional $ resource that you need to budget for :-)

One should of course calculate the available alternatives. I just wanted
to say that using the USB enige of a PIC is not free, unless you happen
to have everything to spare that is needed by the USB code. And AFAIK
the uChip USB code is for C18 only, so you must use that compiler.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: www.voti.nl/hvu
 

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