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RS232 problem with Internal Oscillator

 
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cypher



Joined: 05 Oct 2007
Posts: 31

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RS232 problem with Internal Oscillator
PostPosted: Thu Jan 17, 2008 5:44 pm     Reply with quote
Hi,
I'm having some trouble with getting my printf command working. I'm using a PIC18LF6722 (the low power version). I'm using the internal osciallator at 4MHz. I do not have a serial driver such as a MAX232. The RX and TX go straight from the PIC to the serial port. All I get on the output is some garbage. Here's the code:

Code:

#include <18F6722.h>
#device ADC=10
#include <stdio.h>
#include <math.h>
#include <ctype.h>
#include <stdlib.h>

#fuses INTRC,NOWDT,NOLVP
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, parity=N, bits=8)

void main(void)
{
printf("Hello World");
}


I know the MAX232 inverts the serial pins, but since I didn't have one, I used the invert parameter in the *use rs232 directive, but the complier complained with the following command:

USE parameter value is out of range H/W USART can not invert

Any suggestions what I'm missing?
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Thu Jan 17, 2008 6:03 pm     Reply with quote
Quote:

I know the MAX232 inverts the serial pins, but since I didn't have one, I used the invert parameter in the *use rs232 directive, but the complier complained with the following command:


See the sample #use rs232 statement in this thread.
http://www.ccsinfo.com/forum/viewtopic.php?t=26607

See these threads for more about the 22K series resistor on the Rx pin
of the PIC (when using a software UART directly connected to the PC):
http://www.ccsinfo.com/forum/viewtopic.php?t=32568
http://www.ccsinfo.com/forum/viewtopic.php?t=28707
cypher



Joined: 05 Oct 2007
Posts: 31

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PostPosted: Thu Jan 17, 2008 6:32 pm     Reply with quote
Thanks! That worked. I don't have a 22K, but a 1K in series. But it works.
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