mdio

An API to simplify Management Data Input/Output (MDIO) interface access, including an implementation of the standard Media Independent Interface Management (MIIM) protocol.

Terminology

In the general discourse, MDIO and MIIM are often used to refer to the same thing. In this crate, MDIO is used to refer to the two-pin (MDIO, MDC) I/O interface, while MIIM is used to refer to the standard MII Management protocol that is communicated via the MDIO pins.

By distinguishing between the two in this manner, we create room in the API for both the standard MIIM protocol while also allowing to support non-standard protocols on the MDIO interface, a practise that is not uncommon on some Ethernet switches.

The mdio::Read and mdio::Write traits.

These should be implemented for interfaces where, given 16 control bits, an MDIO operation can be performed.

These traits are designed to allow MDIO interfaces to support both standard MIIM as well as custom variations on the protocol. For example, it is not uncommon for some Ethernet switches to support extended register access by modifying the standard MIIM protocol slightly, i.e. setting the Op code bits to 0b00, or using some of the PHY address bits to increase the number of register addresses.

Note that it may not be possible to implement these traits directly for some MCUs in a manner that allows for both using the integrated MAC while also supporting customised protocols. This is because some MCUs provide limited MAC interfaces that only support the standard MIIM protocol. In these cases, while not ideal, the traits can be implemented for "bit-banging" interfaces instead. This crate provides one such interface via the bitbang feature.

Features

• bitbang: Enables the bb module along with an bb::Mdio type providing a bit-banged implementation of the mdio::Read and mdio::Write traits.

All of these features are opt-in and disabled by default.