Chapter 10 follow behaviors

ch-10/1-follow/follow.py

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+import robot
+import time
+import pid
+
+robot.left_distance.distance_mode = 1
+
+max_speed = 0.9
+set_point = 15
+
+robot.left_distance.start_ranging()
+
+follow_pid = pid.PID(0.1, 0, 0)
+last_time = time.monotonic()
+print("Starting")
+try:
+  while True:
+    # do we have data
+    if robot.left_distance.data_ready:
+      left_dist = robot.left_distance.distance
+      
+      # get error value
+      error_value = left_dist - set_point
+      
+      # calculate time delta
+      new_time = time.monotonic()
+      time_delta = new_time - last_time
+      last_time = new_time
+
+      # get speeds from pid
+      speed = min(max_speed, follow_pid.update(error_value, time_delta))
+      speed = max(-max_speed, speed)
+
+      # make movements
+      print(f"Dist: {left_dist}, Err: {error_value}, Speed: {speed}")
+      robot.set_left(speed)
+      robot.set_right(speed)
+
+      # reset and loop
+      robot.left_distance.clear_interrupt()
+      time.sleep(0.1)
+
+finally:
+  robot.stop()
+  robot.left_distance.clear_interrupt()
+  robot.left_distance.stop_ranging()

ch-10/1-follow/pid.py

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+class PID:
+  def __init__(self, proportional_k, integral_k, differential_k) -> None:
+    self.proportional_k = proportional_k    
+    self.integral_k = integral_k
+    self.differential_k = differential_k
+
+    self.integral = 0
+    self.last_value = 0
+
+  def update(self, error_value, time_delta):
+    proportional = error_value * self.proportional_k
+
+    self.integral += error_value * time_delta
+    integral = self.integral * self.integral_k
+
+    differentiated_error = (error_value - self.last_value) / time_delta
+    differential = differentiated_error * self.differential_k
+
+    return proportional + integral + differential

ch-10/1-follow/pio_encoder.py

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+import rp2pio
+import adafruit_pioasm
+import array
+
+program = """
+; use the osr for count
+; input pins c1 c2
+
+    set y, 0            ; clear y
+    mov osr, y          ; and clear osr
+read:
+    ; x will be the old value
+    ; y the new values
+    mov x, y            ; store old Y in x
+    in null, 32         ; Clear ISR - using y
+    in pins, 2          ; read two pins into y
+    mov y, isr
+    jmp x!=y, different ; Jump if its different
+    jmp read            ; otherwise loop back to read
+
+different:
+    ; x has old value, y has new.
+    ; extract the upper bit of X.
+    in x, 31             ; get bit 31 - old p1 (remember which direction it came in)
+    in null, 31         ; keep only 1 bit
+    mov x, isr          ; put this back in x
+    jmp !x, c1_old_zero
+
+c1_old_not_zero:
+    jmp pin, count_up
+    jmp count_down
+
+c1_old_zero:
+    jmp pin, count_down
+    ; fall through
+count_up:
+    ; for a clockwise move - we'll add 1 by inverting
+    mov x, ~ osr        ; store inverted OSR on x
+    jmp x--, fake       ; use jump to take off 1
+fake:
+    mov x, ~ x          ; invert back
+    jmp send
+count_down:
+    ; for a clockwise move, just take one off
+    mov x, osr          ; store osr in x
+    jmp x--, send       ; dec and send
+send:
+    ; send x.
+    mov isr, x          ; send it
+    push noblock        ; put ISR into input FIFO
+    mov osr, x          ; put X back in OSR
+    jmp read            ; loop back
+"""
+
+assembled = adafruit_pioasm.assemble(program)
+
+class QuadratureEncoder:
+  def __init__(self, first_pin, second_pin, reversed=False):
+    """Encoder with 2 pins. Must use sequential pins on the board"""
+    self.sm = rp2pio.StateMachine(
+        assembled,
+        frequency=0,
+        first_in_pin=first_pin,
+        jmp_pin=second_pin,
+        in_pin_count=2
+    )
+    self.reversed = reversed
+    self._buffer = array.array('i', [0])
+
+  def read(self):
+    while self.sm.in_waiting:
+      self.sm.readinto(self._buffer)
+    if self.reversed:
+      return -self._buffer[0]
+    else:
+      return self._buffer[0]
+ 

ch-10/1-follow/robot.py

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+import board
+import pwmio
+import pio_encoder
+import busio
+import adafruit_vl53l1x
+
+
+motor_A1 = pwmio.PWMOut(board.GP17)
+motor_A2 = pwmio.PWMOut(board.GP16)
+motor_B1 = pwmio.PWMOut(board.GP18)
+motor_B2 = pwmio.PWMOut(board.GP19)
+
+right_motor = motor_A1, motor_A2
+left_motor = motor_B1, motor_B2
+
+right_encoder = pio_encoder.QuadratureEncoder(board.GP20, board.GP21, reversed=True)
+left_encoder = pio_encoder.QuadratureEncoder(board.GP26, board.GP27)
+
+i2c0 = busio.I2C(sda=board.GP0, scl=board.GP1)
+i2c1 = busio.I2C(sda=board.GP2, scl=board.GP3)
+
+right_distance = adafruit_vl53l1x.VL53L1X(i2c0)
+left_distance = adafruit_vl53l1x.VL53L1X(i2c1)
+
+
+def stop():
+    motor_A1.duty_cycle = 0
+    motor_A2.duty_cycle = 0
+    motor_B1.duty_cycle = 0
+    motor_B2.duty_cycle = 0
+
+def set_speed(motor, speed):
+    # Swap motor pins if we reverse the speed
+    if speed < 0:
+        direction = motor[1], motor[0]
+        speed = -speed
+    else:
+        direction = motor
+    speed = min(speed, 1) # limit to 1.0
+    max_speed = 2**16-1
+
+
+    direction[0].duty_cycle = int(max_speed * speed)
+    direction[1].duty_cycle = 0
+
+def set_left(speed):
+    set_speed(left_motor, speed)
+
+def set_right(speed):
+    set_speed(right_motor, speed)