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Multiple serial ports on one PIC18F8722

 
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dk-info



Joined: 13 Apr 2009
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Location: Melbourne, Florida

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Multiple serial ports on one PIC18F8722
PostPosted: Fri Oct 16, 2009 12:45 pm     Reply with quote
I have an application where I need to control five low bandwidth devices using an RS-232 interface.

I haven't tried it, but how many "soft" UARTS can be programmed on a '8722? I only have to access the serial devices every second or so, at a very low bandwidth (1200 Baud).

Is it reasonable to invoke the "#use rs232() five times? What are the resource consequences?


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David
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PostPosted: Fri Oct 16, 2009 12:50 pm     Reply with quote
See this recent thread:
http://www.ccsinfo.com/forum/viewtopic.php?t=39583
bkamen



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PostPosted: Fri Oct 16, 2009 11:47 pm     Reply with quote
As mentioned in the other thread, multiple software uarts is a no-win situation.

PIC24's come with up to 4 uarts.. then you'd have to add an external 4th.

I hooked an octal uart up to a 18F97J60 recently and got it to work - but it needs a lot of optimization.

A PIC24 would have been better for that too.. the customer wanted to try the 97J60 first though..


It can be done - but it's not pretty. :D

-ben
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asmallri



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PostPosted: Sun Oct 18, 2009 4:04 am     Reply with quote
bkamen wrote:
As mentioned in the other thread, multiple software uarts is a no-win situation.


I disagree. 5 low speed software UARTS all at a constant baud rate is a walk in the park but not using the #use RS232 mechanism.

5 serial ports at 1200 baud could be implemented using high priority interrupts and a single timer. High priority to leave low priority to other functions.
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