DP83825EVM: DP83825 with i.MX RT1042 – “Cannot Initialize PHY” during Ethernet init

Part Number: DP83825EVM

Hello,

I am interfacing a DP83825 Ethernet PHY evaluation board with an i.MX RT1042 MCU.

The i.MX RT1040 EVK originally uses a KSZ8081 PHY. I removed the KSZ8081 and its related jumpers, then connected the RMII signals (TXD[1:0], RXD[1:0], TX_EN, CRS_DV, MDC, MDIO, RESET, REF_CLK) from the i.MX RT1042 to the DP83825 EVM using jumper wires.

I am running the NXP MCUXpresso SDK Ethernet example, but the application prints:

Cannot initialize PHY

Notes

• Ethernet MAC initializes; failure happens during PHY init.

• I am still using the default KSZ8081-based PHY driver from the NXP SDK.

• The XI/XO pins on the DP83825 EVM are left in their default (onboard crystal) configuration.

• The DP83825 EVM has an onboard MCU, which I am not using. I want to interface the PHY directly with the i.MX RT1042.

Questions

1. Does the NXP Ethernet example require a dedicated DP83825 PHY driver, or can KSZ8081 driver be adapted?

2. Could issues like PHY address, reset/strap timing, or RMII REF_CLK source/direction cause the PHY init failure?

3. Can keeping the XI/XO crystal connections on the DP83825 EVM cause problems when using an external MAC?

4. Is there any guide or application note on using the DP83825 EVM with an external MCU, bypassing the onboard MCU?

Any pointers or reference designs would be appreciated.

Thank you.