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RS232 - number of Stop Bits

 
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spesh



Joined: 28 Mar 2006
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RS232 - number of Stop Bits
PostPosted: Tue Mar 28, 2006 8:05 am     Reply with quote

I need to talk to a device using 9600 baud, 8 data bits, No Parity, 2 stop bits. Is this possible with the PIC and if so, how do I set it up ? I can't see anywhere that specifies the number of stop bits used.

Regards

Alan
mpfj



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PostPosted: Tue Mar 28, 2006 8:56 am     Reply with quote

You need to put the PIC into 9 bit serial mode, and always set the 9th bit to a '1' when you send a character.

This will give you ...

<1 x START> <8 x DATA, 1 x STOP> <1 x STOP>

Simple, eh ? Very Happy
spesh



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PostPosted: Tue Mar 28, 2006 9:26 am     Reply with quote

I'm unfamiliar with using 9-bit mode. Can I get the compiler to do this automatically or do I have to access the config registers directly ?

Any pointers (excuse the punn) very much appreciated

Cheers

Alan
SherpaDoug



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PostPosted: Tue Mar 28, 2006 9:28 am     Reply with quote

BTW, If you are only listening to the device, you can listen with 1 stop bt. It is only when you transmit to it that it needs a little extra delay between bytes so a second stop bit is added.
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Ttelmah
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PostPosted: Tue Mar 28, 2006 9:33 am     Reply with quote

The compiler can do it directly (bits=9). You have a 'choice', of sending 9 bit values to the I/O routines (using int16's), or of accessing the bit in the RS232_ERRORS byte. Older compilers only support the latter. The supplied RS485 driver, uses 9 bit mode, so you can see how it is done in this.

Best Wishes
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