Thanks Darrel,
At the Piclist I found some signed 32bit math routines. I copied the add, subtract and the needed support routines (addba and negateb) as add and subtract is the only 32bit ops I need (at the moment at least).
After some trial and error I managed to get these working on the 18F2431 by replacing the skpnc with btfsc, STATUS, C and clrc with bcf STATUS, C. I also made it so that the REGA, REGB and MTEMP variables are declared as PBP variables and then preceeded by an underscore in the actual ASM code. I saved it as a separate file and INCLUDE it in the program together with DT-Ints and inc_PID.
I've replaced my LONG-ops in the DoServo code with calls to these routines, it compiles with PBPW and as far as I can currently see it runs correctly. I haven't tried to apply any step-pulses to see what it does "in real life" but I used TMR1 to time the DoServo routine (including the PID) and worst case I've seen so far is 207uS. ~100% increase in performance compared to when compiled with PBPL.
I've also sent various variables (like the 4 bytes 'building' the 32bit position variable and the pid_Error variable) to the PC and it all looks to be correct. I need to test this much much more but what I'm currently worried about is if there are some bank-switching or RAM issues that I need to take into consideration with these math routines.
I consider it pure luck that I've got it working this far and I'm afraid once I'll start to add more variables and code I'll break it - and I'll have no clue why.
/Henrik.
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