Phillip,

your interrupt rate is actually pretty low. You only have to handle
one byte from the GPS, and/or one keystroke, per interrupt. That's a
tiny amount of ISR code. Your problem is not because of too many
interrupts.

(I'm assuming here that you're not attempting to decode the entire
NEMA message in one interrupt. Do that in the background, or use a
state machine in the interrupt.)

It should definitely work with both of them as high priority
interrupts. I use pic18f in this mode frequently, and it works fine.

One problem: the PIC interrupt doesn't save FSR registers. If your ISR
code uses them, then you could be in for trouble. But I would imagine
that the C library should deal with that. I don't know, because I do
mine in assembler.

Neil



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