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Serial Rx problem

John van Kleisterlee

I have a strange problem in my code. I cannot receive characters via the serial port.

I've read up on the TI and RI interrupts and I think I am handling these correctly.

The program goes to the serial I/O isr, but just sits at the gets(comin,4) line. When I examine comin in the watch window and input chars via the SIN = xx (where xx is an ascii code), I can see the comin array remains empty.

Below is the serial I/O interrupt routine (my application does not need Tx)

pre
void uart_rx_isr (void) interrupt 4 using 3
{ signed char index=0; EA=0;

if (RI == 1) { gets(comin,4); command = atoi(comin); } RI=FALSE; /* finished isr - clear flag */ TI=FALSE; /* TI will not be used - always clear it*/ EA=1;
}

/pre

Here is a fragment from main() - you can see that I set TI=1 initially to set the UART up

pre

TI=TRUE; /* always set TI=1 initially to allow serial printing */ RI=0;

loop: //RI=0; //IDLE

while ((1));

goto loop;
} /pre

Appreciate some pointers here.

Jason

Parents
  • 0 in reply to ImPer Westermark

    Thanks Per and Stephen.

    I will re-structure the interrupt to collect chars one at a time. Its clear this is not optimal

    For the atoi() problem, I can easily add an alpha char to the front of the string. I always terminate these command strings with a '\n' so this should sort that issue out if I check this and then do the atoi() afterwards.

    Anyway, I'll be off line for a few days - other problems to deal with right now.

    Again, appreciate the help.

    Jason.

Reply
  • 0 in reply to ImPer Westermark

    Thanks Per and Stephen.

    I will re-structure the interrupt to collect chars one at a time. Its clear this is not optimal

    For the atoi() problem, I can easily add an alpha char to the front of the string. I always terminate these command strings with a '\n' so this should sort that issue out if I check this and then do the atoi() afterwards.

    Anyway, I'll be off line for a few days - other problems to deal with right now.

    Again, appreciate the help.

    Jason.

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