Permanent Way Network Module


The Network module is a sub-module of the P-Way module. It allows for different networking standards to be implemented which may change during the development of Thinking Trains.

Initially it is planned to develop a 100Base-T Ethernet module, with a possible WiFi module to follow.

Physical Interface

The P-Way network interface comprises two connectors. One or both may be utilised by a network module, or two modules may be fitted at once if they do not require the same connector. Standoffs support rigid mounting of any configuration and offer convenient alignment with the rear panel for one or two modules.

Hirose DF9 board-to-board mezzanine connectors are to be used. These are reliable for high speed signals, repluggable and polarised.

Hardware Interface

CN1 provides all of the signals required to connect an Ethernet PHY and magnetics utilising a MAC internal to the P-Way module SoC.

CN2 provides all of the signals required to connect a WiFi SoC such as an ESP32, or a wired serial connection.

Software Interface

The P-Way software stack provides an abstraction for communication between modules so the physical layer can be changed without affecting the rest of the software stack. Each network module must provide its own abstraction implementation.

Abstracted functions include discovery, sending and receiving messages to and from another station and sending and receiving broadcast messages. Two concurrent interfaces are supported.

100Base-T Ethernet Module

The P-Way module SoC has an Ethernet MAC and exposes an RMII interface to the Ethernet module on CN1. The Ethernet module need provide only a PHY and an RJ45 connector with integrated magnetics and LEDs.

The network stack for this module runs on the P-Way processor via a network abstraction.

802.11 WiFi Module

For WiFi (or indeed Bluetooth or a similar stack) the networking stack runs on the network module and interfaces with the P-Way processor via a UART. An ESP32 SoC with integral antenna will provide this functionality and has the capability to be extended with Bluetooth functionality, e.g. for direct communication with trains.

The software for this module has two portions - the ESP32 networking stack on the module and the network abstraction on the P-Way processor.