Using 2 uarts at once

Ringo42 · Joined: 07 May 2004 Posts: 263

I want to build a device that talks to 2 devices serially. They will be at different baud rates, and the only thing the pic needs to do is translate. Basically ready a few bytes at 19200, send them out the other port at 1Mb, then get a 1Mb response, and send it back at 19200.
My question is should I go with 1 uart, and a software uart, or find a pic like a 18f4680 that has 2 uarts? If I go with the 1 Uart I have to poll to get info from the SW uart, if I go with a 18f4680 , can I set up 2 different #int_RDA routines? How does that work?
Thanks
Ringo
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Ringo Davis

Ken Johnson · Joined: 23 Mar 2006 Posts: 197 Location: Lewisburg, WV

To answer the 2nd part,

#INT_RDA

and then
#INT_RDA2

For the 1st part, 1M is pretty darn fast - not sure you can. Others?

Ken

ckielstra · Joined: 18 Mar 2004 Posts: 3680 Location: The Netherlands

Are the communications full-duplex or half-duplex? i.e. is the sequence exactly as you described where there is only one action at a time (half-duplex), or is it possible you are listening at one port while transmitting at another port (full-duplex)?

In the half-duplex situation you could assign the soft UART to the 19k2 connection and use the hardware UART for the 1Mb connection. For a full-duplex it will be very difficult to implement with a software UART.

Either case: If you have the option open to choose a new chip with two hardware UARTs I would go for that as it makes writing the software a lot easier. A software UART does not generate interrupts and makes the software a lot more difficult. Price is not a criterium as a chip like the PIC18F65J10 with two UARTs is available for $2.15.

Note: the PIC18F4680 has only 1 hardware UART.