diff --git a/ch-12/3-always-face-north/code.py b/ch-12/3-always-face-north/code.py
new file mode 100644
index 0000000..6fd3acb
--- /dev/null
+++ b/ch-12/3-always-face-north/code.py
@@ -0,0 +1,63 @@
+import robot
+import pid_controller
+import asyncio
+import time
+
+# PID Loop control for IMU face north
+class FaceNorthController:
+    def __init__(self):
+        self.pid = pid_controller.PIDController(0.01, 0.010, 0)
+        self.target = 0
+
+    def update(self, dt, angle):
+        error = self.target - angle
+        if error > 180:
+            error -= 360
+        elif error < -180:
+            error += 360
+        control_signal = self.pid.calculate(error, dt)
+        robot.set_left(control_signal)
+        robot.set_right(-control_signal)
+
+
+# control loop
+async def control_loop():
+  controller = FaceNorthController()
+  last_time = time.monotonic()
+  while True:
+    await asyncio.sleep(0.1)
+    next_time = time.monotonic()
+    dt = next_time - last_time
+    last_time = next_time
+    angle = robot.imu.euler[0]
+
+    controller.update(dt, angle)
+    robot.uart.write(f"{angle}, 0\n".encode())
+
+# main
+async def main():
+  await control_loop()
+
+def check_status():
+  sys_status, gyro, accel, mag = robot.imu.calibration_status
+  print(f"Sys: {sys_status}, Gyro: {gyro}, Accel: {accel}, Mag: {mag}")
+  robot.uart.write(f"Sys: {sys_status}, Gyro: {gyro}, Accel: {accel}, Mag: {mag}\n".encode())
+  return sys_status == 3
+
+
+while not check_status():
+  time.sleep(0.1)
+
+print("Ready to go!")
+robot.uart.write("Ready to go!\n".encode())
+# Wait for start signal
+while True:
+  if robot.uart.in_waiting:
+    command = robot.uart.readline().decode().strip()
+    if command == "start":
+      break
+    else:
+      print("Unknown command: {}".format(command))
+  time.sleep(0.1)
+
+asyncio.run(main())
diff --git a/ch-12/3-always-face-north/pid_controller.py b/ch-12/3-always-face-north/pid_controller.py
new file mode 100644
index 0000000..a09358f
--- /dev/null
+++ b/ch-12/3-always-face-north/pid_controller.py
@@ -0,0 +1,27 @@
+class PIDController:
+    def __init__(self, kp, ki, kd, d_filter_gain=0.1, imax=None, imin=None):
+        self.kp = kp
+        self.ki = ki
+        self.kd = kd
+        self.d_filter_gain = d_filter_gain
+        self.imax = imax
+        self.imin = imin
+        self.reset()
+
+    def reset(self):
+        self.integral = 0
+        self.error_prev = 0
+        self.derivative = 0
+
+    def calculate(self, error, dt):
+        self.integral += error * dt
+        if self.imax is not None and self.integral > self.imax:
+            self.integral = self.imax
+        if self.imin is not None and self.integral < self.imin:
+            self.integral = self.imin
+        # Add a low pass filter to the difference
+        difference = (error - self.error_prev) * self.d_filter_gain
+        self.error_prev += difference
+        self.derivative = difference / dt
+
+        return self.kp * error + self.ki * self.integral + self.kd * self.derivative
diff --git a/ch-12/3-always-face-north/pio_encoder.py b/ch-12/3-always-face-north/pio_encoder.py
new file mode 100644
index 0000000..b831bf4
--- /dev/null
+++ b/ch-12/3-always-face-north/pio_encoder.py
@@ -0,0 +1,84 @@
+import rp2pio
+import adafruit_pioasm
+import array
+import asyncio
+
+
+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])
+        asyncio.create_task(self.poll_loop())
+
+    async def poll_loop(self):
+        while True:
+            await asyncio.sleep(0)
+            while self.sm.in_waiting:
+                self.sm.readinto(self._buffer)
+
+    def read(self):
+        if self.reversed:
+            return -self._buffer[0]
+        else:
+            return self._buffer[0]
diff --git a/ch-12/3-always-face-north/robot.py b/ch-12/3-always-face-north/robot.py
new file mode 100755
index 0000000..847f5de
--- /dev/null
+++ b/ch-12/3-always-face-north/robot.py
@@ -0,0 +1,69 @@
+import board
+import pwmio
+import pio_encoder
+import busio
+import adafruit_vl53l1x
+import math
+import busio
+import adafruit_bno055
+
+uart = busio.UART(board.GP12, board.GP13, baudrate=9600)
+
+wheel_diameter_mm = 70
+wheel_circumference_mm = math.pi * wheel_diameter_mm
+gear_ratio = 298
+encoder_poles = 28
+ticks_per_revolution = encoder_poles * gear_ratio
+ticks_to_m = (wheel_circumference_mm / ticks_per_revolution) / 1000
+m_to_ticks = 1 / ticks_to_m
+
+
+motor_A2 = pwmio.PWMOut(board.GP17, frequency=100)
+motor_A1 = pwmio.PWMOut(board.GP16, frequency=100)
+motor_B2 = pwmio.PWMOut(board.GP18, frequency=100)
+motor_B1 = pwmio.PWMOut(board.GP19, frequency=100)
+
+right_motor = motor_A1, motor_A2
+left_motor = motor_B1, motor_B2
+
+right_encoder = pio_encoder.QuadratureEncoder(board.GP20, board.GP21)
+left_encoder = pio_encoder.QuadratureEncoder(board.GP26, board.GP27, reversed=True)
+
+i2c0 = busio.I2C(sda=board.GP0, scl=board.GP1)
+i2c1 = busio.I2C(sda=board.GP2, scl=board.GP3)
+
+left_distance = adafruit_vl53l1x.VL53L1X(i2c0)
+right_distance = adafruit_vl53l1x.VL53L1X(i2c1)
+imu = adafruit_bno055.BNO055_I2C(i2c0)
+
+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 abs(speed) < 0.1:
+        motor[0].duty_cycle = 0
+        motor[1].duty_cycle = 1
+        return
+    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)
diff --git a/ch-12/robot.FCStd b/ch-12/robot.FCStd
new file mode 100644
index 0000000..6ee165f
Binary files /dev/null and b/ch-12/robot.FCStd differ