Svc::ComStub (Passive Component)
1. Introduction
Svc::ComStub is an example F´ component implementing the
communication adapter interface required
to work with F´ communication components. Projects and users may choose to replace this with a complete communication
implementation (i.e. a component managing a specific radio) once ready. As long as any communication implementation
implements the communication adapter interface it can drop in and work with the standard F´ uplink and downlink setup.
Svc::ComStub delegates to a Drv.ByteStreamDriver in order to send and receive data through the driver interface.
2. Assumptions
Using Svc::ComStub assumes that the driver layer (e.g. Drv::TcpClient) provides all capability needed to establish
communications. For example, a project can communicate over raw tcp rather than requiring additional protocol on top of
tcp.
3. Requirements
| Requirement | Description | Rationale | Verification Method |
|---|---|---|---|
| SVC-COMSTUB-001 | Svc::ComStub shall accept Fw::Buffer for transmission and pass them to a Drv::ByteStreamSend port |
The comm interface must send Fw::Buffers through a driver |
Unit Test |
| SVC-COMSTUB-002 | Svc::ComStub shall send a Fw::Success:SUCCESS signal via an Fw.SuccessCondition port on Drv::ByteStreamSend success |
Successful sends must notify any attached Svc::ComQueue |
Unit Test |
| SVC-COMSTUB-003 | Svc::ComStub shall send a Fw::Success:FAILURE signal via an Fw.SuccessCondition port on Drv::ByteStreamSend failure |
Failed sends must notify any attached Svc::ComQueue |
Unit Test |
| SVC-COMSTUB-004 | Svc::ComStub shall retry sending to Drv::ByteStreamSend on Drv::ByteStreamSend retry |
Sends indicating RETRY should be retried. |
Unit Test |
| SVC-COMSTUB-005 | Svc::ComStub shall pass-through Fw::Buffer from a Drv::ByteStreamRead on Drv::ByteStreamSend success |
A Comm interface must receive Fw::Buffers from a driver |
Unit Test |
4. Design
The diagram below shows the Svc::ComStub port interface. Svc::ComStub is a basic Communication Adapter and can be
used alongside the other F´ communication components (Svc::Framer, Svc::Deframer, Svc::ComQueue).
Svc::ComStub Uplink and Downlink Interface
Svc::ComStub implements the
communication adapter interface by
delegation to a Drv::ByteStreamDriverModel as a way to transmit data and receive data. Other communication
adapter implementations may follow-suite.
4.1. Ports
ComStub has the following ports. The first three ports are required for the communication adapter interface, the
second three are because the implementation delegates to a Drv.ByteStreamDriverModel. Only the communication adapter
interfaces ports are required for replacements to Svc::ComStub, however; a Drv.ByteStreamDriverModel ports may still
be useful
Communication Adapter Interface Ports
| Kind | Name | Port Type | Usage |
|---|---|---|---|
sync input |
comDataIn |
Drv.ByteStreamSend |
Port receiving Fw::Buffers for transmission out drvDataOut |
output |
comStatus |
Svc.ComStatus |
Port indicating success or failure to attached Svc::ComQueue |
output |
comDataOut |
Drv.ByteStreamRecv |
Port providing received Fw::Buffers to a potential Svc::Deframer |
Byte Stream Driver Model Ports
| Kind | Name | Port Type | Usage |
|---|---|---|---|
sync input |
drvConnected |
Drv.ByteStreamReady |
Port called when the underlying driver has connected |
sync input |
drvDataIn |
Drv.ByteStreamRecv |
Port receiving Fw::Buffers from underlying communications bus driver |
output |
drvDataOut |
Drv.ByteStreamSend |
Port providing received Fw::Buffers to the underlying communications bus driver |
4.2. State, Configuration, and Runtime Setup
Svc::ComStub has only stores a boolean m_reinitialize indicating when it should send Fw::Success::SUCCESS in
response to a driver reconnection event. This is to implement the Communication Adapter Protocol of a
communication adapter interface.
4.3. Port Handlers
4.3.1 comDataIn
The comDataIn port handler receives an Fw::Buffer from the F´ system for transmission to the ground. Typically, it
is connected to the output of the Svc::Framer component. In this Svc::ComStub implementation, it passes this
Fw::Buffer directly to the drvDataOut port. It will retry when that port responds with a RETRY request. Otherwise,
the comStatus port will be invoked to indicate success or failure. Retries attempts are limited before the port
asserts.
4.3.1 drvConnected
This port receives the connected signal from the driver and responds with exactly one READY invocation to the
comStatus port. This starts downlink. This occurs each time the driver reconnects.
4.3.1 drvDataIn
The drvDataIn handler receives data read from the driver and supplies it out the comDataOut port. It is usually
connected to the Svc::Deframer component