negative HEX to bytes

[cpayne]

I think its 2.50A PBPro

[skimask]

I think its 2.50A PBPro

If you're using 2.50A, and an 18F, then you can use LONG's, which will handle signed integers, both in the math and in the display.
But you want to take a -255 to 255, with a range of 512 integer values, and fit that into a byte value, which has a range of 0 to 255, a total of 256 integer values.
Do you want to lose that 'resolution'? Or do you actually mean something else?