Lpc2000

>    From: Mukadder Ceyhan <mukadder_c@...>
> 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@...
MicroProcessor Engineering Ltd - More Real, Less Time
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