BallPal

I led firmware architecture and systems integration for an autonomous robotic collector built on Raspberry Pi and Python. I wrote 100% of the motor control and navigation codebase, coordinating with a mechanical engineer on hardware integration. The project achieved 2nd place in the NYU Tandon Nick Russo Award, with a high object retrieval success rate during trials.

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Code for Raspberry Pi 5

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# Import necessary libraries

import cv2

import numpy as np

import lgpio

from time import time, sleep

# Initialize GPIO chip

h = lgpio.gpiochip_open(0)

# Define motor GPIO pins

IN1, IN2 = 22, 20

IN3, IN4 = 12, 16

motor_pins = [IN1, IN2, IN3, IN4]

# Define ultrasonic sensor pins

TRIG, ECHO = 4, 17

# Configure motor pins as outputs

for pin in motor_pins:

lgpio.gpio_claim_output(h, pin)

# Configure ultrasonic sensor pins

lgpio.gpio_claim_output(h, TRIG)

lgpio.gpio_claim_input(h, ECHO)

# Initialize camera

cap = cv2.VideoCapture(0)

cap.set(cv2.CAP_PROP_FRAME_WIDTH, 320)

cap.set(cv2.CAP_PROP_FRAME_HEIGHT, 240)

# Define HSV color range for detecting orange

lower_orange = np.array([9, 130, 130])

upper_orange = np.array([22, 255, 255])

# Basic movement control functions for robot

def motor_forward(): #moves forward

lgpio.gpio_write(h, IN1, 1)

lgpio.gpio_write(h, IN2, 0)

lgpio.gpio_write(h, IN3, 1)

lgpio.gpio_write(h, IN4, 0)

def motor_left(): #moves left

lgpio.gpio_write(h, IN1, 0)

lgpio.gpio_write(h, IN2, 1)

lgpio.gpio_write(h, IN3, 1)

lgpio.gpio_write(h, IN4, 0)

def motor_right(): #moves right

lgpio.gpio_write(h, IN1, 1)

lgpio.gpio_write(h, IN2, 0)

lgpio.gpio_write(h, IN3, 0)

lgpio.gpio_write(h, IN4, 1)

def motor_reverse(): #moves backward

lgpio.gpio_write(h, IN1, 0)

lgpio.gpio_write(h, IN2, 1)

lgpio.gpio_write(h, IN3, 0)

lgpio.gpio_write(h, IN4, 1)

def motor_stop(): #stops moving

for pin in motor_pins:

lgpio.gpio_write(h, pin, 0)

# Brush VEX motor control setup

vex_IN3 = 19

vex_IN4 = 26

ENB = 18 #This pin is for power control of the motor

# Configure Brush VEX motor pins

lgpio.gpio_claim_output(h, vex_IN3)

lgpio.gpio_claim_output(h, vex_IN4)

lgpio.gpio_claim_output(h, ENB)

# Function to move brush VEX motor forward at given speed (0–100%)

def vex_motor_forward(speed_percent):

lgpio.gpio_write(h, vex_IN3, 1)

lgpio.gpio_write(h, vex_IN4, 0)

lgpio.tx_pwm(h, ENB, 10000, speed_percent)

# Stop brush VEX motor

def vex_motor_stop():

print("Stopping motor")

lgpio.gpio_write(h, vex_IN3, 0)

lgpio.gpio_write(h, vex_IN4, 0)

# Read distance from ultrasonic sensor

def get_distance():

lgpio.gpio_write(h, TRIG, 1)

sleep(0.00001)

lgpio.gpio_write(h, TRIG, 0)

pulse_start = time()

while lgpio.gpio_read(h, ECHO) == 0:

pulse_start = time()

pulse_end = time()

while lgpio.gpio_read(h, ECHO) == 1:

pulse_end = time()

duration = pulse_end - pulse_start

distance = round(duration * 17150, 2)

return distance

# Core behavior loop: zigzag, track ball, avoid obstacles

def move_zigzag():

zigzag_state = 0 # Keeps track of zigzag direction

while True:

distance = get_distance()

print(f"Distance: {distance} cm")

# Read camera frame

ret, frame = cap.read()

if not ret:

continue

# Apply HSV mask for orange ball detection

hsv_frame = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)

mask = cv2.inRange(hsv_frame, lower_orange, upper_orange)

contours, _ = cv2.findContours(mask, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)

# Check if ball is detected

ball_detected = False

ball_x = None

for cnt in contours:

area = cv2.contourArea(cnt)

if area > 300:

ball_detected = True

x, y, w, h = cv2.boundingRect(cnt)

ball_x = x + w // 2

break

if ball_detected: #when ball is detected…

print("Ball Detected - Tracking Faster!")

frame_center = frame.shape[1] // 2

reaction_time = 0.2

# Turn left toward ball

if ball_x < frame_center - 60:

print("Adjusting Left for .2 s")

motor_left()

start_time = time()

while time() - start_time < reaction_time: #this loop makes camera constantly update

ret, frame = cap.read()

if ret:

hsv_frame = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)

mask = cv2.inRange(hsv_frame, lower_orange, upper_orange)

cv2.imshow("Camera Feed", frame)

cv2.imshow("Orange Mask", mask)

if cv2.waitKey(1) & 0xFF == ord('q'):

return

# Turn right toward ball

elif ball_x > frame_center + 60:

print("Adjusting Right for .2 s")

motor_right()

start_time = time()

while time() - start_time < reaction_time: #this loop makes camera constantly update

ret, frame = cap.read()

if ret:

hsv_frame = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)

mask = cv2.inRange(hsv_frame, lower_orange, upper_orange)

cv2.imshow("Camera Feed", frame)

cv2.imshow("Orange Mask", mask)

if cv2.waitKey(1) & 0xFF == ord('q'):

return

# Move forward toward ball

else:

print("Moving Forward Toward Ball for .2 s")

motor_forward()

start_time = time()

while time() - start_time < 0.7: #this loop makes the camera constantly update

ret, frame = cap.read()

if ret:

hsv_frame = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)

mask = cv2.inRange(hsv_frame, lower_orange, upper_orange)

cv2.imshow("Camera Feed", frame)

cv2.imshow("Orange Mask", mask)

if cv2.waitKey(1) & 0xFF == ord('q'):

return

vex_motor_forward(70)

sleep(1.25)

vex_motor_forward(98)

sleep(3)

# Stop after interaction

vex_motor_stop()

motor_stop()

start_time = time()

while time() - start_time < 1.5:

ret, frame = cap.read()

if ret:

hsv_frame = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)

mask = cv2.inRange(hsv_frame, lower_orange, upper_orange)

cv2.imshow("Camera Feed", frame)

cv2.imshow("Orange Mask", mask)

if cv2.waitKey(1) & 0xFF == ord('q'):

return

# Obstacle avoidance

elif distance < 75:

print("Wall detected! Avoiding")

motor_reverse()

sleep(0.8)

motor_stop()

motor_right()

sleep(0.6)

motor_stop()

start_time = time()

while time() - start_time < 1.5: #this loop makes the camera constantly update

distance = get_distance()

ret, frame = cap.read()

if ret:

cv2.imshow("Camera Feed", frame)

cv2.imshow("Orange Mask", mask)

if cv2.waitKey(1) & 0xFF == ord('q'):

return

# Default zigzag movement

else:

print("Zigzagging...")

if zigzag_state == 0:

motor_left()

start_time = time()

while time() - start_time < 0.17: #this loop makes the camera constantly update

distance = get_distance()

ret, frame = cap.read()

if ret:

cv2.imshow("Camera Feed", frame)

cv2.imshow("Orange Mask", mask)

if cv2.waitKey(1) & 0xFF == ord('q'):

return

motor_forward()

zigzag_state = 1

else:

motor_right()

start_time = time()

while time() - start_time < 0.17:

distance = get_distance()

ret, frame = cap.read()

if ret:

cv2.imshow("Camera Feed", frame)

cv2.imshow("Orange Mask", mask)

if cv2.waitKey(1) & 0xFF == ord('q'):

return

motor_forward()

zigzag_state = 0

start_time = time()

while time() - start_time < 0.3: #this loop makes the camera constantly update

distance = get_distance()

ret, frame = cap.read()

if ret:

cv2.imshow("Camera Feed", frame)

cv2.imshow("Orange Mask", mask)

if cv2.waitKey(1) & 0xFF == ord('q'):

return

motor_stop()

start_time = time()

while time() - start_time < 1.5:

distance = get_distance()

ret, frame = cap.read()

if ret:

cv2.imshow("Camera Feed", frame)

cv2.imshow("Orange Mask", mask)

if cv2.waitKey(1) & 0xFF == ord('q'):

return

# Start behavior loop

try:

move_zigzag()

except KeyboardInterrupt: #makes the typical error exception

print("Stopping")

motor_stop()

lgpio.gpiochip_close(h)

cap.release()

cv2.destroyAllWindows()