Purpose

In our IREC competition rockets, we need flight computers to record, telemeter sensor data, control recovery, and track the rocket. To develop our team members' experience with PCB design and programming, we aim to develop our own flight computers. However, monolithic designs that satisfy all of these requirements are complicated to develop and the workload can't easily be spread over a large team. The backplane offers a solution, in a modular architecture in which each module has a specific focus and simpler design. Backplane allows us to spread the work over many team members, resolve issues or upgrade functionality without revising a single large and expensive board. Backplane has 4 modules that communicate using Ethernet. These modules include Sensor, Power, Auto Pilot, and Radio module.  Ethernet has the capability to support future projects that involve high-bandwidth data such as live video and telemetry. Backplane is also compatible with our ground station which uses ethernet.

Backplane

The backplane uses a 5-port SwitchBlox switch to connect all of the modules. It provides the unregulated main power rail, and outgoing DE-9 connections. DE-9 connectors allow backplane to connect to other modules or components located elsewhere in the rocket. DE-9 connectors are positively locking and support enough conductors in a single connector for most use cases

Autopilot module

The ​Autopilot module is designed to control recovery and active control systems.  Example controls include: deployment charges, commanding a reaction wheel, or controlling air brakes.  It has a VoCore V2 single-board computer, which is more powerful than the Cortex M4 microcontrollers the other modules use, to give us the processing power to implement advanced filtering and control systems.

Sensor module

The sensor module measures, logs and distributes sensor readings. The module has two barometric altimeters, two accelerometers , a gyroscope, and two thermometers, and sends these measurements over the Ethernet bus to be sent down by the Radio module and used by the Autopilot module. It also has RS485 to communicate with boards not located in the avionics bay.

Radio module

The radio module provides GPS tracking and communicates with ground receivers using the 900MHz band.

Power module

The Power module regulates the 7-12V power given by the backplane to 5 and 3.3V while it logs the current and voltage on each rail. The 3.3V rail has a maximum current draw of 1700 mA and the 5V rail has a maximum draw of 885 mA.