Microchip Language Jal Doc E0003.JAL

-- 
-- name    : e0003.jal
-- author  : Wouter van Ooijen
-- date    : 21-Sep-1998
-- purpose : jal example
--
-- firmware for a line following robot
-- port B drives 2 4-phase stepper motors via an ULN2803.
-- a0 and a1 are connected to 2 white-is-low reflective sensors.
-- a2 and a3 drive 2 LEDs which show the state of the sensor inputs.

-- target configuration: 16f84 with 10 Mhz Xtal
include 16f84_10

-- standard library
include jlib

-- configure the appropriate port and pin directions
port_b_direction  = all_output 
pin_a0_direction = input 
pin_a1_direction = input 
pin_a2_direction = output 
pin_a3_direction = output 
  
-- provide steering for the two stepper motors
-- and wait the appropriate time (time depends on the
-- stepper motors used). 
procedure steppers( byte in a, byte in b ) is
   port_b = a + ( b << 4 )
   delay_1mS( 10 )
end procedure

-- variables for the current steering of the stepper motors
-- initialised to appropriate intial values 
var byte left_stepper  = 0b_0001
var byte right_stepper = 0b_0001
   
forever loop

   -- copy the sensor values to the indicator LEDs
   pin_a2 = pin_a0
   pin_a3 = pin_a1

   -- step each motor only when the associated
   -- sensor sees white 
   if ! pin_a0 then
      stepper_motor_half_forward( right_stepper )
   end if
   if ! pin_a1 then
      stepper_motor_half_forward( left_stepper )
   end if
   
   -- provide steering and wait
   steppers( left_stepper, right_stepper )

end loop