PIC failure, serial communication and watchdog

[Gon]

Hello,

i use a PIC 18F458 and i wondered if it was possible the make the PIC fail with serial communication ?

I send ascii characters to the PIC, and everythoing works, and it seems that if i type too 'fast' on the keyboard, the pic does not what it should, but it does not reset itself as well although the watchdog is on...

while(counter < 600)
{
restart_wdt();
if(kbhit()) init = getc();
else init = 0;
switch(init)
{
case 'A' : printf("\n\r case 0");
break;
case 'B' : printf("\n\r case 1");
break;
default : printf("\n\r case default");
break;
}
counter++;
delay_ms(100);
}

Would have any explanation or solution ?
Many thanks.
Best regards.

[Gerrit]

Hi Gon,

Try looking at overrun error serial port.

Or make your own interupt handler for serial communication.

Search the forum for ringbuffer en oer (overrun error)

Goodluck,

Gerrit

[Gon]

Ok, many thanks !

My problem is solved i think by handling the overrun error.

But it does not tell me why the watchdog does not reset the pic...

[Gon]

Is it possible that with an overrun error, the pic does not reset by watchdog ?
When i make it fail, I see that the interrrupts are still working, but the main programm is not running like it should, so could the main programm fail without resetting by watchdog and allowing the interrupts to work ?

[Ttelmah]

An 'overrun error', is triggered if you do not handle serial characters fast enough. Now the problem in your code, is that receipt of a single character, can result in fifteen characters being sent back. There are only a couple of characters of hardware buffering (at best) in each direction, so, if three characters arrive quickly, there will be a hardware overrun.
The hardware overrun itself, will not trigger a watchdog timeout. It only disables the UART, not the processor itself. You could write your code to force a watchdog timeout, by having it so that the restart_wdt call, is only called of the overrun error flag is not set. This is down to _you_.
better by far, to buffer the serial transmission, then thie problem would not arrive.

Best Wishes

[Gon]

Thank you very much Ttelmah for your answers.

So, you mean that although i have a restart_wdt() and that, in this case, the UART is disabled, my programm is still kind of running so it won't reset by watchdog, but not doing what it should do ?

I solved the serial problem and i think i won't have this case anymore but i need to understand really what was wrong !
Because in this case, the watchdog was not useful at all but it should be !

[Ttelmah]

[Gon]

Hello,

Thanks again for answers.
This is exactly what i have done.

But last question : the trouble is if you look at my programm, i putted a
while(counter < 600), that means that when counter will be 600 (because the incrementation is done after), it should get out of this loop but it does not...
Does it mean that whatever the main programm has done, if an overrun error occurs, it is not doing anything else ?

Whatever if the UART is disabled, can't my counter makes it out of the loop ?

[Ttelmah]

There is not enough of your code, to know what is really likely to happen. First, the timings involved?. How fast is the PIC running?. What interval are characters likely to come at?. What is the baud rate?. What happens to the wacthdog, outide this loop?. How is 'counter' declared?. If (for instance), counter is declared as an int, then the loop will never exit since an int, cannot reach 600...

Best Wishes

[Gon]

[Guest]

UP !

[Gon]

Is the kbhit function still working, if uart is disabled ?

And please a suggestion for this :

[ckielstra]

[Gon]

I tested thing a lot of time before, and do it every day maybe 50 times for a long time now, and i know this is working.

[Gon]

I will test it again i think i may be wrong in the time i should wait...
Hope so ...

Thanks for help!