[CircularLogic]

If my memory serves me right, all pwm values are usigned chars (which gives them the 0 - 255) range. If you subract 127 from anything less than 127, it is going to wrap around to 255 because it cant handle negative signs.

If I am right about the pwm variables all being unsigned chars, then your problem is subtracting the 127 from the value. The fix would to be create a temporary integer variable, give it the value of the pwm, do the math, and then reassign it.

int temp13 = pwm13;
int temp14 = pwm14;
int temp15 = pwm15;
int temp16 = pwm16;
if (p1_sw_trig == 1)
{
pwm13 = (temp13-127)/2+127;
pwm14 = (temp14-127)/2+127;
pwm15 = (temp15-127)/2+127;
pwm16 = (temp16-127)/2+127;
}



Also, as posted above, you could just cast it to an int.