Lily∞Bot With Raspberry PI Pico W: Obstacle Avoidance With 3.3V Sonar Sensor

I updated the open-source robot, Lily∞Bot to work with the Raspberry PI Pico W programmed in MicroPython.

• Lily∞Bot robot from NoireSTEMinist.com/shop
• Or build the Lily∞Bot using the CAD and 3d printer files on Github at https://github.com/berry123/Lily-Bot
• Microcontroller should be a Raspberry PI Pico W
• Need one LED with 220 ohm resistor
• One HC-SR04 3.3V sonar sensor

1. The figures below the text indicate how to connect circuit elements using the nodes on the breadboard, the pinout for the Raspberry Pi Pico W and the Fritizing schematic for this circuit.
2. Use the following steps to wire the TB6612 motor driver, sonar and LED to the Raspberry PI Pico W
3. Put the TB6612 motor driver in one end of the breadboard with the USB connection at the end near the end of the breadboard.
4. Connect the left motor to motor A (red, blk) on the TB6612
5. Connect the right motor to motor B (red, blk) on the TB6612
6. Use two wires to connect VCC and VM on the TB6612 to VBUS on the Raspberry PI Pico W. One option is to put VBUS on a row of the breadboard and use wires to connect there.
7. Use a wire to connect PWMA on the TB6612 motor controller to pin 28 on Raspberry PI Pico W
8. Use a wire to connect AIN2 on the TB6612 motor controller to pin 27 on Raspberry PI Pico W
9. Use a wire to connect AIN1 on the TB6612 motor controller to pin 26 on Raspberry PI Pico W
10. Use a wire to connect BIN1 on the TB6612 motor controller to pin 22 on Raspberry PI Pico W
11. Use a wire to connect BIN2 on the TB6612 motor controller to pin 21 on Raspberry PI Pico W
12. Use a wire to connect PWMB on the TB6612 motor controller to pin 20 on Raspberry PI Pico W
13. Use these steps to wire up the LED and sonar circuit before writing the program.
14. The following first two circuits show the nodes for meeting points on a breadboard and the Raspberry PI Pico W wiring diagram
15. Put the 220 ohm resistor on the breadboard with each leg in a different row.
16. Put the LED in the breadboard with the short leg on the same row as the 220 ohm resistor
17. Put the long leg of the LED on a different row and connect the long leg of the LED to pin 18
18. Use a wire to connect the other leg of the 220 ohm resistor to ground.
19. Use the sonar mount to connect the sonar to the front of Lily∞Bot.
20. Use a wire to connect the VCC pin on the sonar to the 3.3 V (OUT) pin on the Raspberry PI Pico W. This pin is 5th from the top on the right
21. Use a wire to connect the GND pin on the sonar to any ground pin on the Raspberry PI Pico W.
22. Use a wire to connect the TRIG pin on the sonar to pin 17 on the Raspberry PI Pico W.
23. Use a wire to connect the ECHO pin on the sonar to pin 16 on the Raspberry PI Pico W.

1. Open up PlatformIO Visual Studio and create a.py file
2. Configure the file as a MicroPico project
3. Copy the file code into the file and then save.
4. Right click on the file name and select "Run current file on Pico"

#obstacleAvoicance.py CAB 9.17.23
#This code will drive the LilyBot forward
#then turn when obstacle is detected with sonar
#https://www.noiresteminist.com/shop


#Carlotta Berry 9.14.23


from machine import Pin, ADC, PWM
from utime import ticks_us, sleep_us, sleep_ms


#define inputs and outputs
ledPin = 18
triggerPin = 17
echoPin = 16
trigger = Pin(triggerPin, Pin.OUT)
echo = Pin(echoPin, Pin.IN)
led = Pin(ledPin, Pin.OUT)
pin = Pin("LED", Pin.OUT)

#define inputs and outputs
PWMA = PWM(Pin(28))
AIN2 = Pin(27, Pin.OUT)
AIN1 = Pin(26, Pin.OUT)
PWMA.freq(60)


BIN1 = Pin(22, Pin.OUT)
BIN2 = Pin(21, Pin.OUT)
PWMB = PWM(Pin(20))
PWMB.freq(60)
motorSpeed = 65535


def reverse():
    AIN1.value(1)
    AIN2.value(0)
    BIN1.value(1)
    BIN2.value(0)
    PWMA.duty_u16(motorSpeed)
    PWMB.duty_u16(motorSpeed)


def forward():
    AIN1.value(0)
    AIN2.value(1)
    BIN1.value(0)
    BIN2.value(1)
    PWMA.duty_u16(motorSpeed)
    PWMB.duty_u16(motorSpeed)


def pivot():
    AIN1.value(0)
    AIN2.value(0)
    BIN1.value(0)
    BIN2.value(1)
    PWMA.duty_u16(motorSpeed)
    PWMB.duty_u16(motorSpeed)


def stop():
    AIN1.value(0)
    AIN2.value(0)
    BIN1.value(0)
    BIN2.value(0)


def distance():
    timepassed=0
    signalon = 0
    signaloff = 0
    trigger.low()
    sleep_us(2)
    trigger.high()
    sleep_us(5)
    trigger.low()
    while echo.value() == 0:
        signaloff = ticks_us()
    while echo.value() == 1:
        signalon = ticks_us()
    #print(signalon)
    #print(signaloff)
    timepassed = signalon - signaloff
    #print(timepassed)
    dist_cm = (timepassed*0.0343)/2
    if dist_cm>60:
        dist_cm=60
    return dist_cm


print("Obstacle Avoidance on Lily∞Bot...")


while True:
    reading = distance()
    print(reading)


    if reading<10:
        led.value(1)
        stop()
        sleep_ms(100)
        reverse()
        sleep_ms(500)
        pivot()
        sleep_ms(500)
        reading = distance()
    else:
        led.value(0)
        forward()
        sleep_ms(100)
        reading = distance()

1. Watch the following video to confirm that your circuit is working correctly.
2. If it is not, try to debug the code and trouble shoot the circuit wiring.