2_Ports_and_SimoSim Directory Reference

Detailed Description

Ports and SimoSimo

Introduction

This document explains basic principle of ports of Simo and how to use them in SimoSim.

Connecting Modules with ports

Ports allow to create connections between modules. The class Simo::Port is a templated class and it is the base class. Any protocol can be built on top of it. To create a new port class, it is required to implement is the bool connect(Port* other) method in the subclass. This method is called when two ports are connected together and this is what SimoSim uses to connect the ports.

Some templated implementations are already provided in the library to ease integration:

• Simo::InPort<T>: Allows to receive a payload of type T. It connects to a Simo::OutPort<T>
• Simo::OutPort<T>: Allows to send a payload of type T. It connects to a Simo::InPort<T>
• Simo::BidirectionalPortTyped<OutPayload, InPayload>: Allows to send a payload of type OutPayload and receive a payload of type InPayload. It connects to another Simo::BidirectionalPortTyped<InPayload, OutPayload> (notice that OutPayload and InPayload are swapped).
• Simo::BidirectionalPort<T>: It is an alias for Simo::BidirectionalPortTyped<T, T>. It is a good general-purpose port in case bidirectional communication is needed of the same payload type.

Look at Simo/port/Port.h for the implementation of these classes. Here below a recap of the methods that Simo::BidirectionalPort<T> provides:

+------------------------------------+
|              [Port A]              |
|  - send_out / clear_out works on X |
|  - receive_in / clear_in works X   |
+------------------------------------+
        |                    ^
        | X goes             | Y goes
        | from A             | from B
        | to B               | to A
        v                    |
+------------------------------------+
|              [Port B]              |
|  - receive_in / clear_in works X   |
|  - send_out / clear_out works on Y |
+------------------------------------+

No specific protocol is enforced and both sides of the port can remove the payload anytime. This is a design choice to allow more flexibility.

Connecting ports in SimoSim

The configuration file of SimoSim allows to connect using the connections section. Look at system_config.yaml for an example:

connections:
  - ping_module/port: pong_module/port

Here ping_module and pong_module both expose a port named port, and these two are connected together. Look at tests/collection/PingPongCollection.cc for the implementation of these modules and how the ports are defined. Inside a module, a port can be created with the Simo::Module::create_port<{Port-Class}>({port_name}) method.

To run this example, you need the PingPongCollection. This is built by default when Simo is built. To run the example, use the following command:

SimoSim --config <EXAMPLE_PATH>/system_config.yaml --search-path <SIMO_BUILD_PATH>