42131-cat-bulldozer: Add RC project.

Author: laurensvalk

sets/technic/42114_88010.jpg

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+---
+title: "Cat® D11 Bulldozer"
+number: 42131
+image:
+    local: "42131-cat-bulldozer.jpg"
+layout: set
+description: "Add set description"
+---

sets/technic/42131-cat-bulldozer/42131-cat-bulldozer.jpg

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+---
+title: "Powered Up Remote Control"
+maintainer:
+    user: "pybricks"
+    name: "The Pybricks Team"
+image:
+    local: "42131-cat-bulldozer-remote.jpg"
+description:
+    "Control the Cat Bulldozer with the Powered Up Remote!"
+video:
+    youtube: "N7OmW-7u8fA"
+building_instructions:
+    external:
+    - https://www.lego.com/cdn/product-assets/product.bi.core.pdf/6403271.pdf
+    - https://www.lego.com/cdn/product-assets/product.bi.core.pdf/6403276.pdf
+code: "#program"
+---
+
+
+# Program
+
+This program lets you drive and operate the Cat® D11 Bulldozer using the
+Powered Up remote control. No smartphone required!
+
+When the program begins, it resets the function selector to the zero position,
+corresponding to the blade up and down movement. You can select any function
+by pressing the *green button* along with one of the gray buttons. This will
+change the remote light and switch the function selector as follows:
+
+* Left ＋ (blue): Moves the blade up and down.
+* Left − (red): Tilts the blade back and forth.
+* Right ＋ (yellow): Moves the ladder up and down.
+* Right − (green): Moves the ripper up and down.
+
+Once the function is selected, use the red buttons to control the motor that
+powers the selected function.
+
+Use the gray buttons to control the tracks. You can change
+the ``DRIVE_ACCELERATION`` value in the code to a lower value to make the
+vehicle start and stop driving more gradually. You can also change the speed
+by reducing the ``DRIVE_SPEED`` value.
+
+
+{% include copy-code.html %}
+```python
+{% include_relative main.py %}
+```
+# Credits
+
+This program was inspired by Pybricks user AVCampos' program first shared on
+[Eurobricks](https://www.eurobricks.com/forum/index.php?/forums/topic/182012-42131-cat-d11-bulldozer/&page=46&tab=comments#comment-3455837). Be sure
+to check out his code and [video](https://www.youtube.com/watch?v=gy3nFvojZ2o)
+for additional inspiration.
+
+And thanks to Jim van Gulik who lent his bulldozer to the Pybricks team to
+make this program and video.

sets/technic/42131-cat-bulldozer/index.md

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+from pybricks.pupdevices import Motor, Remote
+from pybricks.parameters import Button, Color, Direction, Port
+from pybricks.tools import wait, StopWatch
+
+# Connect to the remote.
+remote = Remote()
+
+# Default speed and acceleration. You can change
+# them to make it more realistic.
+SWITCH_SPEED = 720
+DRIVE_SPEED = 1000
+DRIVE_ACCELERATION = 2500
+FUNCTION_POWER = 100
+
+# Initialize the motors.
+left_motor = Motor(Port.A, Direction.COUNTERCLOCKWISE)
+right_motor = Motor(Port.B)
+function_motor = Motor(Port.C)
+switch_motor = Motor(Port.D)
+
+left_motor.control.limits(acceleration=DRIVE_ACCELERATION)
+right_motor.control.limits(acceleration=DRIVE_ACCELERATION)
+
+# Buttons paired with the green button to make a command.
+COMMANDS = {
+    Button.LEFT_PLUS: ("Blade up/down", 0, Color.BLUE),
+    Button.LEFT_MINUS: ("Blade tilt", 270, Color.RED),
+    Button.RIGHT_PLUS: ("Ladder", 180, Color.YELLOW),
+    Button.RIGHT_MINUS: ("Ripper", 90, Color.GREEN),
+}
+
+# Find the right end left endstop positions
+right_end = switch_motor.run_until_stalled(500, duty_limit=50)
+left_end = switch_motor.run_until_stalled(-500, duty_limit=50)
+
+# The full switch motion ranges 270 degrees. Everything beyond that
+# is play towards the endstops, equal in both directions. Since we
+# are currently at the left endpoint, we can reset the angle
+# accordingly. This way, the functions # are simply at the
+# relative positions 0, 90, 180, 270.
+switch_motor.reset_angle(-(right_end - left_end - 270) / 2)
+
+
+def switch_target(target_angle):
+    # Try up to 5 times.
+    for i in range(5):
+
+        # Keep track of how long we've tried.
+        watch = StopWatch()
+        switch_motor.run_target(SWITCH_SPEED, target, wait=False)
+
+        # Wait until the stopwatch times out.
+        while watch.time() < 2000:
+            wait(10)
+            # We're done if the motor is on target, so exit
+            # this function.
+            if switch_motor.control.done():
+                return
+
+        # Otherwise, we got stuck, so try wiggling around to
+        # release it.
+        print("Getting unstuck.")
+        switch_motor.run_target(SWITCH_SPEED, 0, wait=False)
+        wait(1500)
+        switch_motor.run_target(SWITCH_SPEED, 270, wait=False)
+        wait(1500)
+
+
+while True:
+
+    # Check which buttons are pressed
+    wait(10)
+    pressed = remote.buttons.pressed()
+
+    # If the center button is pressed, process the
+    # corresponding command.
+    if Button.CENTER in pressed:
+
+        # Stop driving
+        right_motor.stop()
+        left_motor.stop()
+        function_motor.stop()
+
+        # Go through the commands.
+        for button, command in COMMANDS.items():
+
+            # Check if the command has a matching button.
+            if button in pressed:
+
+                # Now we can unpack the command.
+                name, target, color = command
+
+                # Execute command.
+                print("Selected:", name)
+                remote.light.on(color)
+                switch_target(target)
+
+                # Wait for the button to be released.
+                while button in remote.buttons.pressed():
+                    wait(10)
+
+    # Activate function_motor motor based on the red buttons.
+    if Button.LEFT in pressed:
+        function_motor.dc(FUNCTION_POWER)
+    elif Button.RIGHT in pressed:
+        function_motor.dc(-FUNCTION_POWER)
+    else:
+        function_motor.stop()
+
+    # Choose drive speed based on +/- buttons.
+    left_speed = 0
+    right_speed = 0
+    if Button.LEFT_PLUS in pressed:
+        left_speed += DRIVE_SPEED
+    if Button.LEFT_MINUS in pressed:
+        left_speed -= DRIVE_SPEED
+    if Button.RIGHT_PLUS in pressed:
+        right_speed += DRIVE_SPEED
+    if Button.RIGHT_MINUS in pressed:
+        right_speed -= DRIVE_SPEED
+
+    # Activate the driving motors.
+    left_motor.run(left_speed)
+    right_motor.run(right_speed)