Autopilot Architecture

This page details the high-level design behind the autopilot code.

RTOS

The main autopilot systems are built on FreeRTOS, an open-source Real-Time Operating System. FreeRTOS gives us the ability to run multiple concurrent tasks on a single embedded system, each of which has a priority and can "block" for a period of time while they wait for data. At any given time, the highest priority task that is not blocking will be running.

A few notes about developing for real-time systems:

• Treat timeouts as a design error. Most blocking OS functions on the autopilot allow (or require) specifying a timeout for the blocking operation.

Autopilot Drivers

Required:

• GPS
• XBee
• Altimeter
• IMU
• Interchip
• EEPROM

Optional:

• Airspeed
• Battery
• Ultrasonic

Safety Drivers

Required:

• PWM
• PPM
• Interchip

Autopilot Logic

Required:

• Task management
• PID
• Waypoint management
• Navigation
• Telemetry
• Autonomous level
• EEPROM storage
• Startup codes

Optional:

• Sensor fusion
• Landing/take off
• Multi-vehicle

Safety Logic

Required:

• Anonymous level
• Safety switch
• PPM disconnect
• Startup codes
• SPI heartbeat