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from ARM uart port to multiple outputs to devices..

Started by Mukadder Ceyhan November 24, 2005
Hi all!

I am designing an ARM based embedded control board
which has two uart port. One port is dedicated to an
external standalone device, and the other uart port
will be used for many IO devices, such as printer, RF
radio, POS terminal etc..The problem is to make this
single uart port availeble to these multiple devices,
multiplexing maybe?

Any suggestions doing this easily?
Is there any IC doiing such a this thing?

thanks..
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An Engineer's Guide to the LPC2100 Series

Mukadder Ceyhan wrote:

>Hi all!
>
>I am designing an ARM based embedded control board
>which has two uart port. One port is dedicated to an
>external standalone device, and the other uart port
>will be used for many IO devices, such as printer, RF
>radio, POS terminal etc..The problem is to make this
>single uart port availeble to these multiple devices,
>multiplexing maybe? >
Multiple SPI UARTs maybe: MAX3100

TomW --
Tom Walsh - WN3L - Embedded Systems Consultant
http://openhardware.net, http://cyberiansoftware.com
"Windows? No thanks, I have work to do..."
----------------


> From: Mukadder Ceyhan <mukadder_c@muka...>
> Subject: from ARM uart port to multiple outputs to devices..
>
> I am designing an ARM based embedded control board
> which has two uart port. One port is dedicated to an
> external standalone device, and the other uart port
> will be used for many IO devices, such as printer, RF
> radio, POS terminal etc..The problem is to make this
> single uart port availeble to these multiple devices,
> multiplexing maybe?

If you have relatively low baud rates (say 9600 baud), you can
generate bit-bang serial ports quite easily. Use a timer to
generate an interrupt at (say) four times the baud rate, and use
a pair of state machines for the receive and transmit routines.
The idle receive state polls for the start bit, waits two
interrupt times, and then polls the data every four interrupt
times.

We use this scheme with three additional serial ports and it
works well. You can reduce jitter by using the FIQ interrupt.
With a bit of jiggery-pokery you can run each port at different
baud rates.

Stephen --
Stephen Pelc, stephen@step...
MicroProcessor Engineering Ltd - More Real, Less Time
133 Hill Lane, Southampton SO15 5AF, England
tel: +44 23 80 631441, fax: +44 23 80 339691
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