Svc::FileDownlink Component

Svc::FileDownlink Component

1 Introduction

FileDownlink is an active ISF component. It manages downlink of files from the spacecraft.

2 Requirements

Requirement	Description	Rationale	Verification Method
FD-001	Upon command, 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

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.

3.2 Block Description Diagram (BDD)

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
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.

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.

The initial value is IDLE.

3.6 Commands

FileDownlink recognizes the commands described in the following sections.

3.6.1 SendFile

SendFile is an asynchronous command. 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.

When File Downlink receives this command, it carries out the following steps:

1. If mode = CANCEL, then

   a. Issue a DownlinkCanceled event.

   b. set mode = IDLE and return.

2. Set mode = DOWNLINK.
3. Open the file sourceFileName for reading with file descriptor d. If there is any problem opening the file, then issue a FileOpenError warning and abort the command execution.
4. Invoke bufferGetCaller to request a buffer whose size is the size of a START packet. Fill the buffer and send it out on bufferSendOut.
5. Set a remainder r to the size of the file with descriptor d.

6. While r > 0 and mode = DOWNLINK do:

   a. Let n be the smaller of downlinkPacketSize and r.

   b. Invoke bufferGetCaller to request a buffer B whose size is the size of a DATA packet with a data payload of n bytes.

   c. Read the next *n* bytes out of the file with descriptor *d*.
   

   If there is any problem reading the file, then issue a FileReadError warning, close the file, and abort the command execution.

   d. Fill *B* with (i) the data read the previous step and (ii) the appropriate
   

   metadata. Send B out on bufferSendOut.

   e. Reduce *r* by *n*.
   

7. Close the file with descriptor d.

8. If mode = CANCEL, then

   a. Invoke bufferGetCaller to request a buffer whose size is the size of a CANCEL packet. Fill the packet and send it out on bufferSendOut.

   b. Issue a *DownlinkCanceled* event.
   

9. Otherwise invoke bufferGetCaller to request a buffer whose size is the size of an END packet. Fill the buffer and send it out on bufferSendOut.
10. Set mode = IDLE.

3.6.2 Cancel

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

4 Dictionary

Dictionaries: HTML MD

5 Checklists

Document	Link
Design	Link
Code	Link
Unit Test	Link

6 Unit Testing

TODO