Define CLOCK_FREQUENCY = 4

Dim phase1 As Byte
Dim phase2 As Byte
Dim phase3 As Byte
Dim phase4 As Byte

phase1 = %010001
phase2 = %100001
phase3 = %100010
phase4 = %010010

TRISGPIO = %001000

direction:
If GPIO.3 = 0 Then Goto reverse

GPIO = phase1
WaitMs 25
GPIO = phase2
WaitMs 25
GPIO = phase3
WaitMs 25
GPIO = phase4
WaitMs 25
Goto direction

reverse:
GPIO = phase1
WaitMs 25
GPIO = phase4
WaitMs 25
GPIO = phase3
WaitMs 25
GPIO = phase2
WaitMs 25
Goto direction