PSAS/ SoftwareFunctionalSpecJune2003

Title and Scope

Software Functional Specification

This document gives a functional description of Flight Computer software to be created for the June 2003 launch.

Phrases in bold italic are gaps to be filled in and solicitation of better description.

Hardware Architecture

fig1\ hardware.png

Figure 1 gives a brief overview of the hardware connections to/from the Flight Computer. This figure is a simple block diagram intended only to show basic connections of the Flight Computer. For more details of the hardware, consult the hardware specifications at FlightComputer and BlockDiagram.

The Flight Computer has an attachment to the CAN bus, over which it exchanges CAN messages with the Pyro/2m, GPS, IMU, ATV and APS (Avionics Power System) nodes.

The Flight Computer has a connection to an IEEE 802.11 WiFi transceiver, over which it exchanges message with the Ground Station.

The Flight Computer has 128MB (32MB x 32) of non-volatile flash memory used as a "flash" hard disk (for program and data storage).

Software Architecture

fig2\ software.png

Amendment: SMART distributes its own IMU messages instead of sending to the CAN reader

The Flight Computer software will be implemented as a set of cooperating processes which exchange message by reading and writing named pipes. Figure 2 shows the process boundaries and message flows.

Manager Process

The Manager Process supervises all the other processes. It is responsible for:

missing: how does Manager communicate with Ground Station?

Message Formats

There are three message formats:

CAN Reader Process

Reads from the CAN bus. Converts messages from CANbus message format to Fifo message format.

CAN Writer Process

Converts messages from Fifo message format to CANbus message format. Writes to the CAN bus.

?FC2Net Process

Implements WiFi downlink to Ground Station.

?Net2FC Process

Implements WiFi uplink from Ground Station.

Logger Process

Implements a non-volatile log of all CAN messages. Expects and writes messages in Fifo message format.

SMART Process

Smart Module Assembling Realtime Tasks

Process imu, gps, etc. data to determine position in space. Detect launch, apogee etc. Dispatch virtual CAN message to Logger, ?FC2Net, and Sequencer (position updates).

Transform GPS serial data into position messages Jamey, need better description here

Transform IMU messages from Jamey, need better description here

Sequencer Process

Implements the flight state machine.

Larry, Nate: this would be a good place to embed your state machine design, or a link to it if you have a separate document.

Implements recovery backup timer. better description needed