PIC18f4520 - writting to eeprom address

[chefgage]

Hi,

PIC18f4520
Compiler version 4.057
PIC mounted on a PIC demo board

In simple terms I am writing a value (int8) to a memory address in the eeprom every time an external interrupt happens (which is triggered
by an external switch).

This value is then displayed on a set of LED's when another external interrupt happens (triggered by another switch).

The code for this part is as follows: (when tested this works ok)

[asmboy]

because of the relatively LONG delay to do an EEPROM write

i would NEVER do it inside the ISR - that could be too much time to steal from the foreground.

rather i would declare and use a 1 bit int flag variable set a flag inside the ISR - and then in the MAIN execution loop - do the write and then clear the flag bit for re use by the ISR

here are some of the many of rules i live by when writing an ISR:

inside your handler ......

* no floating point calculations ( and avoid 32 bit int calls too )
* no mult, division or modulo ops
* no trig function calls
* never use a delay statement
* never do a printf()
* never disable other interrupts or only with great care
* never write to eeprom

there are ways around all of these things BASED on coupling to an ISR
but try to never execute these things inside the ISR

[chefgage]

Thanks for that,

As for writing to the next eeprom address each time a button is pressed what would the syntax/code be. When writing to the eeprom I have:

write_eeprom(0,value); // '0' is the address,
// value is the value to be written

I have tried something like:

for (i=0;i++)
write_eeprom(i,value);

But this appears not to work, while I have my working code I would like to get this little bit working before looking at implementing what has been said in the second post

Any ideas?

Thanks

[jeremiah]

[asmboy]