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----- Original Message ----- 
From: "Vitaliy" <spam@maksimov.org>
To: "piclist" <PICLIST@mitvma.mit.edu>
Sent: Monday, February 06, 2006 5:45 AM
Subject: [PIC]: putrsUSART() breaking DataRdyUSART()


> Hello List,
>
> I have a little circuit which uses a PIC18F4320, whose Tx/Rx lines are 
> tied
> together (Tx is connected through a diode, so it can only drive the bus
> low). It's very similar to the Parallax AppMods.
>
> Now, any time I use putrsUSART(), it causes the DataRdyUSART() function to
> stop working. I attached the source code to this message. If you were to
> compile and run it as-is, and type "ABCDEFG" in HyperTerminal, you would
> see:
>
>    AABBCCDDEEFFGG
>
> However, if you were to uncomment the putrsUSART() function, you would 
> get:
>
>    Hello World!
>
>    ABCDEFG
>
> For some reason, after the putrsUSART() function is used, DataRdyUSART()
> never evaluates to TRUE.
>
> A couple of observations:
>
> 1. Closing/opening the port after using the putrsUSART() fixes the 
> problem.
> 2. putcUSART() does not have this issue.
>
> I have a feeling that I am overlooking something very obvious. Any help 
> with
> this matter is greatly appreciated!
>
> Best regards,
>
> Vitaliy
>
> ---------- Source Code -------------------
>
> #include <p18f4320.h>
> #include <delays.h>
> #include <usart.h>
>
> /* Set configuration bits for use with ICD2 / PICDEM2 PLUS Demo Board:
> *  - set HS-PLL oscillator
> *  - disable watchdog timer
> *  - disable low voltage programming
> *  - enable background debugging
> */
>
> #pragma config OSC = HSPLL
> #pragma config WDT = OFF
> #pragma config LVP = OFF
> #pragma config DEBUG = ON
>
> void main(void)
> {
>  char c;
>
>   //Open the USART configured as 8N1 in polled mode
>  OpenUSART (USART_TX_INT_OFF &
>               USART_RX_INT_OFF &
>               USART_ASYNCH_MODE &
>               USART_EIGHT_BIT &
>               USART_CONT_RX &
>               USART_BRGH_LOW, 255);
>
>  //putrsUSART((const far rom char *)"\rHello World!\r");
>
>  while (BusyUSART()); // wait until transmission is complete
>
>   for (;;)
>   {
>      if (DataRdyUSART())  // check USART read buffer
>      {
>         c = getcUSART();           // read character
>         putcUSART(c);              // echo it back
>         while (BusyUSART());       // wait until transmission is complete
>         Delay1KTCYx(4);            // wait some more
>         while (DataRdyUSART())     // empty the receive buffer
>            getcUSART();
>      }
>   }
> } 

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