Ethernet on custom board with STM32H730
I have a custom board with an STM32H730 and a LAN8710A PHY, operated in RMII mode. The board is a new design, based on an older board but with some differences (the older board has an STM32H750). My short-term goal is to prove out the hardware -- a response to a ping would be sufficient for this.
I have no prior experience with the STM32 family. I set up a project with STM32CubeIDE, following the Ethernet video from ControllersTech. I'm at a point where the firmware initializes without error, and seems to correctly set up the PHY. But then I run into problems.
With the board plugged into the building LAN and a scope connected to the RX lines of the PHY, I see activity on those signals. There is, however, no activity on the TX lines going from the processor back to the PHY. And of course there's no response to a ping.
We're outputting a 50 MHz clock from MCO1, and feeding that into ETH_RMII_REF_CLK and into the PHY clock input. That signal looks good.
During setup the firmware queries the registers in the PHY, and the results look reasonable -- for example, I can see that the PHY is correctly in RMII mode.
We're using an 8710 PHY, and the Ethernet driver in the project is for a LAN8742, which has new features and new registers defined. I looked at the list of registers in the driver, and searched the code for their uses. I don't see any setting or queries of registers that are present in the 8742 but missing from the 8710.
With the complexity of memory configuration and all the other setup, I don't know what direction to go in. Any hints on how to approach this would be appreciated.