DP83822HF: STM32H735+DP83822 no MAC found and ping failed

Part Number: DP83822HF

I want to implement UDP communication, but currently it is not working. There are no device MAC found within the local network, and it is also impossible to ping. Could you please help me identify where the problem lies?

As we can see in the circuit diagram, Pin 26 has no external resistor, which causes the default hardware strap mode to lock in the MII mode.

Since I need RMII Master mode, I forced RMII Master mode through the following software configuration and output a 50M clock through GPIO3.

1. RCSR register (0x0017):bit 5 is set to 1, and bit 7 is cleared for RMII Master mode;
2. 0x0462 = 0x4300 for 50MHz of GPIO3;
3. PHYRCR register (0x001F):bit 14 is set to 1 for digital restart;

The waveforms output by the 25M crystal oscillator and GPIO3 (50M) were detected to be normal through the oscilloscope.

The following are the corresponding register values for the cases of network cable disconnected, network cable connected and link up.