PHY Interface Adaptation

Software Architecture

The Ameba Ethernet module integrates the Lightweight TCP/IP stack (LwIP) and MAC driver. The correspondence to OSI and TCP/IP models is shown below:

Ethernet Software Architecture

The SDK implements the L2 MAC driver and the RMII operations, and provides the L1 RTL8201F driver.

Adaptation Steps

To adapt another PHY chip, implement the eth_phy_ops interface table and define the corresponding device instance.

Implement PHY Operations

Implement the key functions in struct eth_phy_ops based on the PHY datasheet.

Note

• Standard PHY registers are defined in ameba_phy.h.

• Registers specific to the PHY chip can be defined directly in a custom ameba_phy_custom.c file, which must be added to CMakeLists.txt.

Taking RTL8201F as an example:

Essential PHY Driver Interfaces

OPS Member	Function	Description	Why Required
.init	phy_rtl8201_init	Init & ID Check Read PHY ID and match with RTL8201_PHY_ID_MATCH.	Prevents matching wrong hardware; ensures PHY is powered and MDIO is working.
.reset	phy_rtl8201_reset	Soft Reset Write BMCR reset bit and wait for stabilization.	Ensures the PHY is in a known initial state and clears earlier faulty configuration or state.
.cfg_refclock	phy_rtl8201_cfg_refclock	Ref Clock Config Switch to Page 7 to set RMII clock direction (Input/Output).	The MAC and the PHY of an RMII interface must share the 50 MHz reference clock. A wrong direction prevents the link from being established.
.cfg_link	phy_rtl8201_cfg_link	Link Config Configure the Auto-Neg advertised capability, or force the speed and duplex mode.	Determines how the PHY connects to the peer switch or router. Without this interface, 10M/100M or duplex mode cannot be set.

Define MDIO Bus Interface and PHY Instance

Define the MDIO bus read/write interface and create the eth_phy_dev instance, specifying the PHY address.

// 1. Define MDIO bus operations
// Use low-level read/write functions provided by SDK
const struct eth_mdio_ops eth_mdio_bus_default = {
    .mdio_read  = Ethernet_ReadPhyReg,
    .mdio_write = Ethernet_WritePhyReg,
};

// 2. Define PHY device instance
struct eth_phy_dev eth_phy_dev_custom = {
    .bus  = &eth_mdio_bus_default, // Bind bus interface
    .addr = 0x01,                  // [Important] PHY Address must match schematic
    .ops  = &custom_phy_ops,       // Bind operations implemented above
};

Register and Initialize

Call Ethernet_StructInit() to fill default handle configuration and bind the custom PHY. The following is a configuration fragment, not complete hardware initialization:

void User_Ethernet_Config(ETH_InitTypeDef *eth_handle)
{
    Ethernet_StructInit(eth_handle, &eth_phy_dev_custom);

    // Fill descriptor, buffer, and application configuration afterwards
}

The handle, PHY instance, and MDIO operations table must remain valid while the driver is in use.