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Need help with RS232

 
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Vlad



Joined: 03 May 2004
Posts: 8

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Need help with RS232
PostPosted: Tue Jun 01, 2004 12:01 pm     Reply with quote
Hi,

I am trying to connect PIC using RS232 to a PC (using HyperTerminal to read from the PIC (18F452)).

The problem is that no matter how I set the parity and data bits with #use RS232 and no matter how I set the HyperTerminal I keep getting wrong characters in HT window. I am reading characters from the keypad and sending them to both the LCD and HyperTerminal to make sure they are the right ones. I have RxD, TxD, GND lines from PC connected to my PIC. I am only attempting transfer from the PIC for now.

Here is the code:

Code:

#include <18F452.h>
#device ICD=TRUE
#device adc=8
#use delay(clock=20000000)
#fuses NOWDT,WDT128,RC_IO, NOPROTECT, NOOSCSEN, BROWNOUT, BORV20, NOPUT, STVREN, NODEBUG, LVP, NOWRT, NOWRTD, NOWRTB, NOWRTC, NOCPD, NOCPB, NOEBTR, NOEBTRB

#use rs232(baud=9600, XMIT=PIN_A0, RCV=PIN_A1, PARITY=N, BITS=8)

.
.
.

while(true)
   {
    k = Key_Read() ;

    if(k=='*') LCD_Clear(1);
    else if (k=='#') LCD_Clear(2);
    else
    {
     LCD_Write(k);    // send character to LCD
     putc(k);         // send character to PC
    }
   }



Characters appear fine on the LCD but in HT I am getting wrong chars. For example instead of '7' i am getting an arrow down, for '8' it erases the line etc.

Thanks,
Vlad
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Tue Jun 01, 2004 12:30 pm     Reply with quote
Quote:
I have RxD, TxD, GND lines from PC connected to my PIC.

You're not using a MAX232 chip, and you're using a soft USART.
Then you need to use the INVERT option in your #use rs232
statement. You should also use a series resistor on the RS232
Rx pin on your PIC. See this thread:
http://www.ccsinfo.com/forum/viewtopic.php?t=19062
Vlad



Joined: 03 May 2004
Posts: 8

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PostPosted: Tue Jun 01, 2004 2:30 pm     Reply with quote
Thank you!

It worked. No MAX232, so I needed that INVERT.

Thanks again,
Vlad
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