1. Don’t Push Me

To prevent Pico 4WD car from running off a cliff, let’s give it a little sense of self-preservation.

In this project, the car will be dormant, and if you push it over the edge of a cliff, it will be awakened, then back up and shake its head in displeasure.

Note

• The complete script project_1_cliff.py is in the path pico_4wd_car\examples\funny_projects.

• In order to allow the car to move on the ground without the USB cable connected, you need to save this script as main.py to Raspberry Pi Pico, see 5. Run Script Offline(Important) for a tutorial.

Below are the steps to implement the cliff function, and you can copy them into Thonny to run them.

1. Import libraries

1. In this project, we use grayscale module, motor and servo, so we import the related libraries here.

   import motors as car
   from servo import Servo
   from grayscale import Grayscale
   import time
   
   # init grayscale module
   gs = Grayscale(26, 27, 28)
   gs.set_edge_reference(1000)
   
   # init servo
   servo = Servo(18)
   servo.set_angle(0)
   
   MOTOR_POWER = 50
   
   
   try:
       while True:
           print(gs.get_value())
           time.sleep(0.05)
   finally:
       pass
   

   • Note that this command gs.set_edge_reference(1000) is the cliff threshold set according to my current environment, what you actually use may be different.

   • Run the script after copying it into Thonny and then hang the car in the air (10cm or more).

     

   • Finallly, fill in a value in gs.set_edge_reference() according to the result in the Shell.

2. Back up when detected

When the grayscale module detects a cliff, go backward; otherwise, stop in place.

import motors as car
from servo import Servo
from grayscale import Grayscale
import time

# init grayscale module
gs = Grayscale(26, 27, 28)
gs.set_edge_reference(1000)

# init servo
servo = Servo(18)
servo.set_angle(0)

MOTOR_POWER = 50


def main():
    while True:
#         print(gs.get_value())
        if gs.is_on_edge():
            car.move("backward", MOTOR_POWER)
        else:
            car.move("stop")

try:
    main()
finally:
    car.move("stop")
    time.sleep(0.05)

3. Shaking head while backing up

To make the car more cute, let it shake its head while backing up.

import motors as car
from servo import Servo
from grayscale import Grayscale
import time

# init grayscale module
gs = Grayscale(26, 27, 28)
gs.set_edge_reference(1000)

# init servo
servo = Servo(18)
servo.set_angle(0)

MOTOR_POWER = 50

def shake_head():
    for angle in range(0, 90, 10):
        servo.set_angle(angle)
        time.sleep(0.01)
    for angle in range(90, -90, -10):
        servo.set_angle(angle)
        time.sleep(0.01)
    for angle in range(-90, 0, 10):
        servo.set_angle(angle)
        time.sleep(0.01)

def main():
    while True:
        # print(gs.get_value())
        if gs.is_on_edge():
            car.move("backward", MOTOR_POWER)
            shake_head()
            shake_head()
        else:
            car.move("stop")

try:
    main()
finally:
    car.move("stop")
    time.sleep(0.05)