Echoing characters with interrupts via rs232 on pic18f452

[ProgGuy]

I'm sending some data (123456789\r) repeatedly from my pc at 38400, data bits=8, stop bits 1 parity=none. When the PIC sees a CR it echoes the entire contents of the buffer to the pc. What I don't understand is that every second transmission echoes garbage back to my pc (ex: 123456789 then 1#$*@! then 123456789 back again). Is there something wrong with my interrupt routine? When typing in the data from hyperterm everything is fine but it fails when it's being streamed. I tried every other baud rate and I still get sporadic garbage. Just in case any of you want to know, I'm using a max232.

Thanks,

Here's my example code.

#if defined(__PCH__)
#include <18F452.h>
#use delay(clock=19660800)
#use rs232(baud=38400, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
#endif


#define BUFFER_SIZE 128
BYTE buffer[BUFFER_SIZE];
BYTE tail = 0;
BYTE receivedFrame = 0;


#INT_RDA
void serial_isr()
{
buffer[tail] = getc();
if(buffer[tail] == '\r' || tail == (BUFFER_SIZE - 1))
{
receivedFrame = 1;
disable_interrupts(GLOBAL);
}
else
{
tail++;
}
}

void main()
{
BYTE head = 0;
enable_interrupts(global);
enable_interrupts(int_rda);

do
{
if(receivedFrame == 1)
{
while(head <= tail)
putc(buffer[head++]);

head = tail = 0;
receivedFrame = 0;
enable_interrupts(global);
}
}
while (TRUE);
}

[Mark]

Try disabling the rda int. The global int will be restored by hardware on the return from int instruction.

[ProgGuy]

I still have the same problem after changing the GLOBAL to INT_RDA. Thanks for the quick reponse though.

[Ttelmah]

[Mark]

[ProgGuy]

Mark,

The driving program works fine. I get the same result if I paste blocks of text in hyperterm. I'm still working on some previous response and will post my results shortly.

Thanks,
ProgGuy