Instant Interrupts - Revisited

[Wirecut]

Hi Darrel,

this is my first post on this comunity. First of all I would thanks for the fantastic DT_INTS-14.bas background PWM routine.

I have uset your SW on a 16F628 in order to drive some LED with different brightness an WORK PEFECTLY. Darrel YOU ARE GREAT!!!!!

Now I need to use a potentiometer so set at run time the brightnes value for the LEDs, and after reading tons of html page and googled for hours, I have the founded suspect that the PBP instruction POT and RCTIME do not work with DT_INTS-14.bas.

Can you please confirm?

Ciao

Leo

[tenaja]

Leo,
Any time you have a routine or command that counts time, an interrupt will cause the timing to be off. Since the POT command times the discharge time of a cap, an interrupt in the middle of it will cause the command to give you a faulty reading when it is resumed.

There are several options;
--turn off the interrupts just before your POT command (and any other timing-specific command), and restore them just after.
--write yourself a home-made "pot" command, and use it inside the interrupts (but this only works if your interrupts are high frequency.)
--use a "real" a/d converter, either one in the PIC or off the chip.

[Wirecut]

Many thanks tenaja for your prompt reply.
Ciao
Leo

[Darrel Taylor]

Many thanks tenaja for your prompt reply.

My sentiments, exactly.
<br>

[tenaja]

Darrel, does your interrupt routine selectively choose which system variables to save, based on which ones are used, to save time? Or, does it save them all, regardless?

[Darrel Taylor]

Saves them all, no matter what.

Without an external program like VBIS for Proton, there's no way to know which system variables are being used by a particular Handler.

But from what I've seen, while optimizing out what isn't used does increase the maximum interrupt frequency available, it only really helps if you're pushing the limits. For normal everyday interrupts (with Basic Language) the extra saves don't have that much effect, and helps provide stability.

And as always, if you really need the speed ?
The interrupts should be in ASM anyways. (no PBP system variables saved at all)

Which is one of the best parts of DT_INTs.
You can have both ASM and Basic Language interrupts in the same program.
<br>

[mister_e]

And all this with a minimum of efforts