F´ Flight Software - C/C++ Documentation  NASA-v1.6.0
A framework for building embedded system applications to NASA flight quality standards.
Svc::FileDownlink Component

Svc::FileDownlink Component

1 Introduction

FileDownlink is an active F´ component that manages spacecraft file downlink. Both operators and components on the spacecraft can add files to the file queue, which FileDownlink will downlink from. Operators can enqueue files using the SendFile and SendPartial commands, and components can enqueue files using the SendFile port. The FileComplete port broadcasts when a file downlink initiated by a port completes, allowing components to detect when a previous enqueued file downlink has completed. To prevent a continuous stream of file downlink traffic from saturating the communication link, a cooldown can be configured to add a delay between the completion of a file downlink and starting on the next file in the queue.

2 Requirements

Requirement Description Rationale Verification Method
FD-001 FileDownlink shall queue up a list of files to downlink The requirement provides the ability to simultaneously queue up multiple files for downlink from different sources Test
FD-002 FileDownlink shall read a file from non-volatile storage, partition the file into packets, and send out the packets. This requirement provides the capability to downlink files from the spacecraft. Test
FD-003 FileDownlink shall wait for a cooldown after completing a file downlink before starting another file downlink Allows a saturated link to process a backlog that may have built up during a file downlink Test

3 Design

3.1 Assumptions

The design of FileDownlink assumes the following:

  1. File downlink occurs by dividing files into packets of type Fw::FilePacket.
  2. One file downlink happens at a time.
  3. Both components and operators must be able to enqueue files, necessitating both a SendFile command and port.

3.3 Ports

3.3.1 Role Ports

Name Type Role
timeCaller Fw::Time TimeGet
cmdIn Fw::Cmd Cmd
cmdRegOut Fw::CmdReg CmdReg
cmdResponseOut Fw::CmdResponse CmdResponse
tlmOut Fw::Tlm Telemetry
eventOut Fw::LogEvent LogEvent

3.3.2 Component-Specific Ports

Name Type Kind Purpose
sendFile Svc::SendFileRequest guarded_input Enqueues file for downlink
fileComplete Svc::SendFileComplete output Emits notifications when a file downlink initiated by a port completes
Run Svc::Sched async_input Periodic clock input used to trigger internal state machine
bufferGet Fw::BufferGet output (caller) Requests buffers for sending file packets.
bufferSendOut Fw::BufferSend output Sends buffers containing file packets.

3.4 Constants

FileDownlink has the following constants, initialized at component instantiation time:

  • downlinkPacketSize: The size of the packets to use on downlink.
  • timeout: Max amount of time in ms to wait for a buffer return before aborting downlink
  • cooldown: The amount of time in ms to wait in a cooldown state before starting next downlink.
  • cycle time: Frequency in ms of clock pulses sent to Run port, used for timing timeouts and cooldown.
  • file queue depth: The maximum number of files that can be held in the internal file downlink queue. Attempting to dispatch a SendFile command or port call while the queue is full will result in a busy error response.

3.5 State

FileDownlink maintains a mode equal to one of the following values:

  • IDLE (0): FileDownlink is idle.
  • DOWNLINK (1): FileDownlink is performing a file downlink.
  • CANCEL (2): FileDownlink is canceling a file downlink.
  • WAIT (3): FileDownlink is waiting for a buffer to be returned before sending another packet.
  • COOLDOWN (4): FileDownlink is waiting in a cooldown period before downlinking the next file.

The initial value is IDLE.

3.6 Commands

FileDownlink recognizes the commands described in the following sections.

3.6.1 SendFile/SendPartial

SendFile is an asynchronous command that adds a file to the file downlink queue. It has two arguments:

  1. sourceFileName: The name of the on-board file to send.
  2. destFileName: The name of the destination file on the ground.

SendPartial also includes the following fields:

  1. offset: Position in file to start reading from.
  2. length: Amount of data to read. A length of 0 reads until the end of file.

When the downlink completes or fails, a CmdResponse packet will be sent indicating success or failure.

3.6.2 Cancel

Cancel is a synchronous command. If mode = DOWNLINK, it sets mode to CANCEL. Otherwise it does nothing.

4 Checklists

Document Link
Design Link
Code Link
Unit Test Link

6 Unit Testing

TODO