Odd behavior if too many instructions

[dksoba]

If I go over 1 page of code (2k words, right?) is there anything I need to worry about w/my current code? I know the pbp code will take care of itself, but my ASM ISR might not. I do use PCLATH for the table jump, so that should be fine. And my GOTO's should be fine so long as the entire ISR is in page0, right?

Thanks,
Matt

[Darrel Taylor]

I do use PCLATH for the table jump, so that should be fine. And my GOTO's should be fine so long as the entire ISR is in page0, right?

You do have PCLATH pointing to the Jump Table. But it doesn't take into account the Jump it makes FROM the table.

If _No_Change, _Decrement, _Increment or _Error end up on the other side of a boundary, it will jump to the wrong place.

As long as the entire ISR is in the same page (doesn't have to be page 0), then it won't have a problem.
The trick is knowing when there is a problem, which you can do easily by adding these lines to the end of the ISR ...

        retfie                  ; Return from interrupt
  if ((high($) & 18h) != (high(ISR) & 18h))
    error ISR crosses page boundary
  endif
ENDASM

If the ISR ends up crossing a boundary, that will flag an error to let you know something needs to be moved.

HTH,

[dksoba]

Thanks for all the help. Because of it I was able to finish the robot project I was working on using optical encoders (instead of potentiometers... PID + nonlinear, 270 degree pots ==slow || messy).

The robot contest was for my senior design class at UCSD (Mechanical Engineering). We had to build a robot to move small pieces of PVC pipe from one rotary table to another rotary table, as fast as possible. The recieving table was at least 1 inch higher than the starting table. Also, the receiving table started out with some positions filled, so you had to at least detect if there was space to move cargo there.

My turntables were stacked. IR sensors were used to detect the presence of pipes on both the top and bottom tables. As soon as a PVC pipe was detected (bottom) or an empty slot detected (top), the PIC would rotate the turntable to that position to align with an air nozzle. The air nozzle shot air between 45-60 PSI at the PVC pipe (there was a round cover for the bottom to prevent the air from just going through the pipe).

My PID was very slow (I was running my motor at around 40% duty cycle MAX) because I was having problems getting my derivative term working well at high speed (worked fine at low speed). I've identified the problem, but it's too late. Our robot was the fastest in the class anyways . We transferred 3 PVC pipes in 1.19-1.86 seconds. I think the second fastest time was on the order of 6 seconds.

Here is a highspeed video of our robot (I think this was our 1.86 second time).



Thanks so much,
Matt

[Darrel Taylor]

Congratulations on the Win!

Looks like it was fun.
Maybe I should go back to school. (Just for the challenges)
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