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Thread: Microcontroller with 4 USARTs and 40 pins
face BY : Keith Causey email (remove spam text)

I like that part too (MAX3100 family) and have used it and its cousins on
several projects. The buffer is advertised to hold 8 bytes but I have never
been able to use it sucesfully. I don't think that a normal read is clearing
the buffer. It seems to assert it's contents to me twice.

> Something else to check out is the I2C UART chips from Maxim.  They have a
> family of chips that has either 232, 485, or logic level serial on one
> and SPI or I2C on the other.  Very cool part.  I also believe they have a
> couple byte buffer to avoid overloading your micro.
> You should be able to find them on their site by searching for 'uart'...
> At 07:25 PM 5/26/00 -0300, Edson Brusque wrote:
> >> Perhaps if you give us a little more information we can help you out
> >
> >    As I'm a musician, and my (piano) keyboard controller doesn't makes
> >the tricks I would like it to do, I'm thinking in developing a MIDI
> >black-box that could do everything I want. Maybe I can sell hundreds of
> >units and make some money :)
> >
> >> It is unlikely that you will find an 8-bit micro with 4 hardware UARTs
> >a
> >> hobbyist), so you probably should plan on finding one with one or two
> >UARTs and
> >> build the rest in software.  If I were in your shoes, I would build
> >all in
> >> software.  If you run a scenix or atmel at 24 MIPs, you'll have exactly
> >768
> >> instructions (scenix, varies for atmel) per bit time to run the UARTs
> >your
> >> user process (at the specified 31.25Kbps).  Divide it by four (bit
> >slicing) and
> >> you end up with 192 instructions to read the state of four RX lines,
> >change the
> >> state of four TX lines, and then do some data processing.  It really
> >not
> >> be too difficult.
> >
> >    I think I'll want to put 16 keys on the thing (8 I/Os for that), an
> >(6 I/Os for that), four MIDI Ins plus four midi Outs (8 I/Os), and I
> >like it to communicate with the PC with Paralell or USB. Even Serial at
> >115.200bps would do the job nicely. Well, this puts 22 I/Os plus PC
> >communication. A 48 or 52 pin Scenix at 50MHz seens to be a very good
> >(I've took a look at SX documentation and it says it can run eight
> >UARTs using 13% of 50MHz). The hard thing will be to make an adaptor to
> >it on a proto-board.
> >
> >    I would also like to put 16 pots on it to control various things
> >volume, pan, reverb, modulation, etc).
> >
> >    I would preffer to make it with PICs, but I don't think it's
possible. I
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<00e201bfcc01$181dc120$16e61018@sttln1.wa.home.com> 7bit

See also: www.piclist.com/techref/io/serials.htm?key=usart
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