As previously stated, half-stepping doubles the resolution of the motor. In our case, we are using a motor with a 5 degree / per step resolution, requiring 72 steps to complete one rotation. By half stepping, we could double this to 2.5 degrees / pulse, requiring 144 steps to complete one rotation. Table 2 shows the step pattern.
There are two ways in which you could implement half-stepping in a PIC. One way would be to drive it directly, using the two previous listings, but replacing the high/low commands with the pins that correspond to each step. The other (and easier) way would be to use a UCN 5804 Stepper Motor IC in conjunction with the PIC.