Description

A standard SnappyXO differential drive robot is the easiest way to use the Path Follower library. This tutorial will guide you through adding a path following feature to your SnappyXO robot.

Robot Requirements

A sample robot using the SnappyXO robotics kit have been put together in this page.

Installation

1. Install the following Arduino libraries from the Arduino library manger or manually download and install.
   1. ArduinoBlue-library (available in the Arduino Library Manager)
   2. L293 Library (available in the Arduino Library Manager)
   3. PathFollower library (download)
2. Install the iOS or Android mobile app from the links below.

Change Bluetooth Module Baud Rate

Change the baud rate of the HM10 as follows:

• In Arduino IDE, under ArduinoBlue example codes, run HM10_console.ino.
• Ensure that the bluetooth module is disconnected and the LED is flashing.
• Set the baud rate to 115200 by issuing following command in the serial monitor window.
• Input the command "AT+BAUD4". This will changes the baud rate on the bluetooth module to 115200 bps.
• You should get this response: "OK+GET:4"
• Disconnect power.

Code

Upload the demo code by opening the Arduino App on your computer.

Go to File → Examples → PreMo - Precise Mover → SnappyXO_PathFollower

Note that this example code has two tabs:

• "SnappyXO_PathFollower" tab contains the pin settings and code related to path following.
• "my_code" tab contains the loop() and setup() functions and this is where your custom code is going to go.

Double check and change these constants in the "SnappyXO_PathFollower" tab:

• RADIUS - Wheel radius in mm.
• LENGTH - Axle length in mm (distance from the left to right wheel).

Hardware Test

Before we upload the code, we need to validate and test the motors, encoders, and the bluetooth module.

1. Uncomment testMotors() in setup() and upload. Observe that the motors move according to the serial monitor prints.
   • If any motors spin in reverse, simply interchange the position of the RED and BLACK wires coming from the motor on the breadboard.
2. Comment testMotors() and Uncomment testEncoders() in setup() and upload. Spin the left and right wheel one revolution, the left and right pulses should be close to PULSES__PER_REV.
3. Run the ArduinoBlue_basic.ino example code with the BLUETOOTH_TX and BLUETOOTH_RX set to the proper pins. Check that the bluetooth functionality is working by moving the joystick. You should see the steering and throttle values change as you move the joystick on the serial monitor.

If any of the above tests fail, the path follower will not work. Troubleshoot and fix them first. Here are some troubleshooting tips:

• Check the electrical connections.
  • Use a multi-meter to do continuity checks.
  • Try neatly rerouting the wires. Messy wires can be confusing and lead to connection errors.
• Check your battery level and make sure power supply is adequate. For example, you cannot draw too much power from the Arduino without bad things happening.

PID Tuning

First, try the provided values in the example code. If that does not work well, try the following.

First set the KD value to zero. Then increase the KP value until the robot can follow a path. Then, try increasing the KD value to improve the path following. The KD is typically much smaller than KP.

Have Fun

Follow these steps to have your robot follow a drawn path!

• In the ArduinoBlue app, got to settings and enable the "Path Feature."
• Connect to your bluetooth module.
• Go to the "Path" tab and draw your path. Then press "Move."
• The robot should follow the path.

The triangle represents the robot location and heading and the blue dot is the goal point that the robot is trying to follow.