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Lab 8 - RFD900x Setup and Firmware Installation Lab

Overview

In this lab, we learned how to set up RFD900x telemetry modules, adjust their communication settings, and communicate between two computers. We also learned how to install custom firmware on the Blue Cube flight controller.

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Activity 1: Setting up RFD900x

Specification Questions

What frequency are these set to? Why? They are placed in the 902-928 MHz frequency band because this is a license-free ISM (Industrial, Scientific, and Medical) frequency band in many countries. Also, the 900 MHz band provides a good trade-off between range and antenna size.

Why do the antennas need to be connected before powering? The antennas must be connected before powering because transmitting without a load can damage the radio’s power amplifier.

What is special about the USB Serial plug? It is an FTDI USB-to-TTL cable with 3.3 V logic, specifically designed for the modem’s interface. It can supply 5V power for programming.

What is pin one on the RFD900 USB Serial Connector, and what color wire connects to it? Please attach a photo before plugging it into your computer's USB. Pin 1 on the RFD900 USB Serial connector corresponds to the black wire of the FTDI cable. You must align the black wire to pin 1 before plugging in the USB to prevent mis-wiring.

What is BAUD? Baud is the number of symbols transmitted per second. For the RFD900, the default serial baud rate is 57,600, and both devices must match this rate to communicate properly.

Adjusting Modem Settings

We used RFDTools on both laptops

We then connected the ground unit to one computer and the air unit to the other computer.

We changed Serial Speed from 57 - 115 and the Net ID to 75

Testing Communication

Each modem was connected to a different laptop

Using PuTTY, we selected the correct port via Device Manager and set the speed to 115200

We opened the serial connection and successfully typed messages back and forth

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Problems Encountered

We forgot to disconnect RFDTools before opening PuTTY, which prevented us from opening some of the software

Some of the terminology (e.g., “baud rate,” “COM port”) was unfamiliar, so we had to stop and look it up

Adjusting the baud settings correctly was a challenge until we learned how to

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Activity 2: Installing Firmware

Specification Questions

The file provided by Windracers has a .apj file extension. What does this mean and why? APJ is a pre-built firmware package for the ArduPilot project. It is also an autopilot open-source software for drones and other robotic vehicles. It includes customised parameter defaults

What is Mission Planner? What are the alternatives to Mission Planner? Mission Planner is a Ground Control Station (GCS) software for ArduPilot. Alternatives include QGroundControl, APM Planner 2, and MAVProxy.

Do you expect the Windracers flight controller firmware to work with Mission Planner? Mission Planner supports loading .apj files for ArduPilot-based hardware. If the firmware from Windracers is compatible with AdruPilot, then I assume the firmware is compatible with Mission Planner.

How much memory does the Blue Cube have? The Blue Cube has 2 MB of flash and 1 MB of RAM.

Installing Firmware

We unscrewed the screws on the back of the blue cube and then connected it to the power module and companion computer

We used the laptop given to us to open Mission Planner

We then inserted the flash drive with the firmware.

We followed the AdruPilot Firmware Loading Guide to upload the .apj file to the Blue Cube Flight Controller

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Testing Connection

We first opened the Windracers Ground Control App on the laptop

We then created a new Serial connecting by adjusting the

Type: Serial

COM Port: COM 9

Baud Rate: 115200

The aircraft then appeared in the menu

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Reflection

This lab was more challenging for us because we were not very familiar with computers, coding, or the terminology needed. At first, we struggled to understand the directions and the vocabulary. However, we learned how to configure the modem communication with RFDTools and PuTTY and connect ground control software to flight hardware.

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