On Tue, 24 Aug 2004 16:13:46 -0500, Cwebber wrote:
> Greetings everyone, I have done very little interfacing between a PIC
> and a PC, and that was with RS-232.  Basically I want to transfer
> 100K samples per second from a 16bit A/D to a PC - preferably using a
> PIC.  Interfacing with an external A/D should be straight-forward,
> and I expect to resolve other problems as they arise.  But I'm not
> sure what method of interfacing with the PC will work the best.  At
> 100K*16bits = 1.6M bps puts me out of the range of rs-232 which tops
> out at 192Kbps.  Several minutes (up to an hour) worth of data will
> be transferred to the PC and later analyzed.
..snip...
> In your experience/opinion is this the best method of transferring
> large amounts of data to a PC?  What are your initial thought on the
> design, am I on the right track or completely off base.  I'm still a
> student and relatively new to PICs and any advice is appreciated.

Have a look at the FTDI FT245BM USB chip. It can easily transfer data
at the speeds you want. I've tested it at close to 500 MB/sec (4Mbps)
with a Rabbit 2000 CPU running at 22MHz. The Rabbit was the bottleneck
as it was simply receiving a packet and resending to the PC as fast as
it could while the USB chip was "always ready" for more data. FTDI also
supplies PC drivers for most of the popular operating systems so it's
pretty much "plug 'n play" -- I got my first module up and running in
about 5 minutes with a terminal program on the PC side.

If you use a 20MHz PIC or greater I think you'll have no trouble
meeting your data transfer rate.

You can even get DIP plug-in modules with the complete USB circuit that
bolts onto a parallel port of the PIC. Dontronics and DLP Design sell
them at a reasonable price.

http://www.ftdichip.com/FTProduct.htm
http://www.dlpdesign.com/usb/usb245.html
http://www.dontronics.com/dlp.html

I'm not sure why more people don't use the FT245 instead of the FT232
(other than it's an 8-bit interface). It's much faster than the FT232
chip and doesn't eat the PIC UART pins, which I normally also have some
other use for.

Matt Pobursky
Maximum Performance Systems

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads