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Software UART on hardware pins?

 
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Will
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Software UART on hardware pins?
PostPosted: Fri Dec 12, 2003 10:21 am     Reply with quote
Hi,
Is it possible to set up a software UART using the hardware UART pins? I would like to use the "invert" option but this isn't available using the hardware UART. I can't see how to tell the compiler not to use the hardware USART.

Will
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Fri Dec 12, 2003 3:35 pm     Reply with quote
Quote:
Is it possible to set up a software UART using the hardware UART pins?

After some experimentation, I found that by using two separate
#use rs232 statements, you can force the compiler to generate
software USART code on the hardware pins. Example:

#include <16F877.h>
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock = 4000000)
#use rs232(baud = 9600, xmit=PIN_C6, INVERT)
#use rs232(baud = 9600, rcv=PIN_C7, INVERT)

main()
{
char c;
putc(0x55);
c = getc();
while(1);
}

This was tested with PCM vs. 3.180. I checked the .LST file
to verify that software USART code has been generated.
Will
Guest
PostPosted: Sat Dec 13, 2003 5:17 am     Reply with quote
Superb. The only slight problem is I am using streams, but this I have solved myself by assigning an OUT and IN stream to the two #use commands:

#use rs232(baud=9600,parity=N,xmit=PIN_C6,bits=8,stream=OUT,INVERT)
#use rs232(baud=9600,parity=N,rcv=PIN_C7,bits=8,stream=IN,INVERT)
#use rs232(baud=38400,parity=N,xmit=PIN_C1,rcv=PIN_C0,bits=8,stream=VFD)

works a dream, thanks. It’s a shame I hadn’t got the hardware the right way as now I have to work in software without the nice hardware buffer/interrupt! Nothing like a software fix to a hardware problem J

Thanks again,

Will
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