Arcade Drive

There are two classic ways of controlling a 2 or 4 wheeled rover that has a tank drive drivetrain.

From xiaoxiae on Github:

Tank drive is a method of controlling the motors of a tank drive drivetrain using two axes of a controller, where each of the axes operate motors on one side of the robot.

In contrast, Arcade drive is a method of controlling the motors of a tank drive drivetrain using two axes of a controller, where one of the axes controls the speed (throttle) of the robot, and the other the steering (spin) of the robot.

---

Rover Setup

Your rover needs the following hardware:

• Flysky receiever
• x2 Rotational servo motors, orientated in tank drive where x1 of the motor sides in inverted/mirrored

Video Tutorial

---

Text Tutorial

Required Library

Before moving forward, ensure you have the following arcade_drive_servo.py and rc.py py files on your CIRCUITPY lib folder.

---

Example Code

import board
import time
from rc import RCReceiver
from arcade_drive_servo import Drive

rc = RCReceiver(ch1=board.D10, ch2=board.D11, ch3=None, ch4=None, ch5=board.D12, ch6=board.D13)
drive = Drive(left_pin=board.D2, right_pin=board.D3, left_stop=0.0, right_stop=0.0)

channels = [1,2,5,6]

# Main code
while True:
    # Read joystick channels
    spin = rc.read_channel(1) # spin
    throttle = rc.read_channel(2) # throttle

    if spin is not None and throttle is not None: # must not be None to do something with the output
        drive.drive(spin,throttle)
        print("spin", spin, "throttle", throttle) # move our motors arcade drive style


    rc.ensure_cycle()  # Maintains sync with our 20ms cycle every loop iteration

Code Breakdown

Importing Necessary Libraries

import board
import time
from rc import RCReceiver
from arcade_drive_servo import Drive

• board: This library provides board-specific constants to specify pins used for input and output. It’s essential to identify which pins on the board connect to devices.
• time: This library allows us to use time-related functions, especially sleep.
• RCReceiver and Drive: These are imported from custom modules. RCReceiver is used to handle the input from the RC receiver, while Drive is used to control the driving mechanism of the robot.

Setting Up the RC Receiver and Drive

rc = RCReceiver(ch1=board.D4, ch2=board.D5, ch3=None, ch4=None, ch5=board.D6, ch6=board.D7)
drive = Drive(left_pin=board.D2, right_pin=board.D3, left_stop=0.0, right_stop=0.0)

• The RCReceiver is initialized with different channels corresponding to different board pins. full tutorial here
• The Drive is set up with pins controlling the left and right servo motors.
  • The pwm servo objects are initialized in the library itself, not in your code.py file.
  • left_stop and right_stop values are set to zero. You can calibrate these values if you find they stop value of 0.0 is not actually causing your servo to stop. [servo stop calibration tutorial]

Main Code Loop

The code enters an infinite loop, constantly checking for input from the RC receiver and updating the drive system accordingly.

while True:
    # Read joystick channels
    spin = rc.read_channel(1)  # spin
    throttle = rc.read_channel(2)  # throttle

    if spin is not None and throttle is not None:  # Ensures valid input
        drive.drive(spin, throttle)  # Moves the motors based on input
    print("spin", spin, "throttle", throttle)  # Displays the current input values

    rc.ensure_cycle()  # Maintains sync with our 20ms cycle every loop iteration

• Reading Channels: The code reads channel 1 for spin and channel 2 for throttle to get joystick input.
• Checking Inputs: It checks if the inputs are not None (meaning valid and connected inputs).
• Driving Motors: If valid data is read, the drive function is called to control the motors according to the joystick’s direction and throttle.
• Print Statement: This outputs the current values of spin and throttle to the console for debugging purposes.
• Delay: A short delay of 20-40 ish milliseconds is added to match the RC receiver’s duty cycle and avoid overwhelming the processor with too many instructions in a short period.

Conclusion

This code effectively allows for controlling a robot using an RC receiver and servo motors. It’s crucial to ensure that the pins and channels are correctly configured to match your hardware setup.