LAN8742A no clock output

[tyassin]

Hi

I am using STM32H753VIT6 together with LAN8742A.

I have some questions regarding the setup.

1. My schematic for the LAN8742A is shown in the picture below. I plan to use the PHY to generate the clock. To my knowledge this requires a pulldown resistor on INTSEL which is done with R420.
nRST is connected to nRST on the MCU and a button is connected to pull it low if needed.

When I power on my board I would expect an output on the REFCLKO (pin 14). But this pin is constantly low?

2. I have also tried to make a project to make a project with ETH and LWIP, but that does not make any difference and there is no output on REFCLKO (pin 14).
In the datasheet for LAN8742A, it is stated that after power-on, nRST need to be asserted. I am a little unsure if this is handle in software when it is setup by STM32CUBE?

Hope somebody have some inputs or even better a solution 🙂

Thank you!

[STea]

Hello @tyassin ,

I think the issue you are facing is either related to the hardware implementation of the PHY and LAN port your using or some software related issue .

we can eliminate the software related issue by trying to run the provided example on STM32Cube_FW_H7_V1.11.1\Projects\NUCLEO-H743ZI\Applications\LwIP\LwIP_HTTP_Server_Netconn_RTOS

which is compatible with the STM32H753 and try to pinpoint the issue by trying at first to see if the PHY is configured correctly by reading the status for example.

back to the NRST time the example which is implemented on the NUCLEO-H743ZI uses the same PHY and has similar NRST timings and this does not impact the PHY behavior even after REST .

After making sure it is not a problem related to the Software it is recommended also to check the resistor values and capacitor as well you can take the NUCLEO-H743ZI schematics as reference .

BR

[tyassin · Accepted solution]

Hi,

Thank you for the answer.
I looked at my hardware again and by close inspection I could see that the crystal for the PHY was actually rotated 90 degrees!!! This was really hard to see as the crystal is almost a square.

But after this was rotated everything works 🙂

Thank you for support.