A CAN based distributed telemetry and telecommand network for a nanosatellite

[摘要] A communications protocol is designed for real time control and data handling for aNanosatellite application. The communication protocol is based on the Controller AreaNetwork (CAN) technology. The protocol handles different message types such as timesynchronization, telecommand messages, telemetry acquisition, unsolicited telemetrymessages, large file transfers and debug messages.The design of the protocol entails finding a suitable target microcontroller in which theprotocol implementation is demonstrated. This requires consideration of a number ofdevelopment factors such as cost, complexity, availability, reliability and operationalenvironment (space). The AVR AT90CAN128 microcontroller was chosen as a targetmicrocontroller as it gave most of the required factors mentioned above.The protocol implementation involves developing low level software drivers, the middlewareand the application programs to demonstrate handling of each supported message. In theimplementation the media access scheme and low layer communication is provided by theCAN low level kernel (physical and data link layers).The protocol performance was evaluated by measuring the software response latencies, thebus throughputs and the software efficiencies. Power consumption due to CANcommunication was also measured.System reliability was tested by loading the CAN bus with extreme communication trafficand letting the system run for a long time. The observation was that messages were handledconsistently.

[发布机构] Stellenbosch University