lost int_rda interrupt

redicon · Joined: 26 Feb 2012 Posts: 8

Can the int_rda be lost?
I mean:
My program has got 2 interrupts, rs232 and Timer1.

I've got a looping code that executes:

asmallri · Joined: 12 Aug 2004 Posts: 1634 Location: Perth, Australia

temtronic · Posted: Mon Mar 05, 2012 6:03 pm

no, I won't say yes..

We need to see a complete but small program that we can compile. Also the PIC type and compiler version.

You can't 'lose' the interrupt, you have to read it first(done in the ISR).

Without seeing your whole program is is impossible to decide what is wrong.

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

You could "lose an int_rda interrupt" if you don't use a receive fifo buffer,
and if you fail to check for incoming characters often enough.

You can largely eliminate this problem by using a buffer, as shown in the
CCS Ex_sisr.c example file. When chars come in, the interrupt occurs
and the chars are put into a circular buffer. Then you don't have to
check so often. If the buffer is large (512 bytes), then depending on
your incoming character rate, maybe you only need to check the
buffer every few hundred milliseconds. Your program can be doing
something else for a long time and if you don't check the buffer it
doesn't matter, because the chars are saved in the buffer during that
time. You can read them when you finished doing other things in your
program. Here is the example file:

Ttelmah · Joined: 11 Mar 2010 Posts: 19360

and, the key thing that nobody has said so far, there _must_ be 'ERRORS' in you #use RS232.

Key to understand, is that the hardware UART has just _under_ two characters of buffering. If at any time the code does not service INT_RDA, and data is arriving continuously, for a period that exceeds this, the UART _will_ flag an ERROR, and _will_ go into a hung state, if ERRORS is not set, _or_ you have your own error handling code in the interrupt. You _must_ have one or the other. If not, from this point on, the receive part of the UART will stop working.

Best Wishes

RF_Developer · Joined: 07 Feb 2011 Posts: 839

Delays are going to mess with interrupts. Precisely how depends on a number of things.

Delays in critical sections, i.e. while interrrupts are turned off, are very bad news. If interrupts are going to work smoothly, critical sections must be as short as possible: no delays.

To avoid "missing" interrupts you must be able to service them as quickly as possible. So ciritcal sections must be short, and delays should be avoided, or at the very least made interruptable (but that implies buffering of incoming and probably out going data, which should probably be the norm anyway).

RF Developer