Training Robot

WIoT final project

Authored by: Farjan Ahmed, Carlos Giron, Ivan Post

This is our final project for CS 4501: Wireless for the Internet of Things. It is a prototype system for controlling a mobile robot over long distances (from our observation, up to 0.32 km) using the LoRa physical layer protocol on Heltec ESP32 v3 LORA boards. It is designed to operate on the 915 MHz unlicensed band in the United States, which means you do not need an amateur radio license to use it. This is a video of an operator controlling the robot from about 0.3 km away; the control latency is primarily due to delays in the video feed and is under 500 ms in practice. The exact feasible range will depend on environmental factors.

We have provided instructions below to reproduce our prototype.

Building the peripheral robot

Components list:

• WiFi LoRa 32 V3 Heltec Board
• 2 Sparkfun Dual tb6612fng Motor Drivers for motor control
• 4 12V DC 100RPM Greartisan Motors
• INIU Portable Power Bank
• ACEIRMC USB Power Delivery Module for requesting 12V from a power bank
• HiLetgo game joystick

Additional pcb relevant components such as resistors, switches, and connectors are shown in this schematic:

The KiCad files for editing the schematic and gerbers for ordering PCBs are included in the "/KiCad" directory.

Mount the breakout boards for motor drivers and modules onto their respective locations on the pcb:

Building the central controller

Pin assignments:

Assignments for the peripheral robot device are as follows:

• 19 - PWMA/B
• 20 - A/BIN1
• 26 - A/BIN2
• 47 - PWMA/B
• 48 - A/BIN1
• 33 - A/BIN2
• Connect external 3v3 supply and gnd

These pins are used to set the direction of motors and speed of motors as they are connected to tb6612fng motor drivers. You MUST NOT power the motor drivers using the 3v3 pins of the Heltec board. Due to a hardware issue it seems that these boards are unable to power the motor drivers and remain on for operation. You must use a seperate 3v3 source to power the drivers.

In our case we used an Arduino Uno R3 to deliver 3v3, but a simple battery should suffice. It is important to remember to ground both Arduino and Heltec on the same rail otherwise reference issues for digital logic occur.

Assignments for the central controller are as follows:

• 7 - Vrx
• 6 - Vry
• 5 - Sw

Although the datasheet recommends using 5V as input, our code was designed around using 3v3.

Deploying the provided code

This project uses PlatformIO, so configuring the project locally should be simple. Flash the Heltec v3 on the robot with the lora-peripheral code, and flash the Heltec v3 on the controller with the lora-central code. Everything should start automatically without any user input.

Starting the robot

After code has been flashed onto the central and peripheral devices start the device as follows:

1. Connect the power delivery module to the power bank's 65 W output port
2. Connect the Arduino to the power bank
3. Connect the Heltec to the power bank
4. Flip the enable switch

If the PD module and onboard led are on then the robot is ready for operation if the devices were flashed successfully and connections were correct.