Svc::ComStub Component

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