cancel
Showing results for 
Search instead for 
Did you mean: 

LAN8742 PHY does not work properly on STM32 F437VIT (Custom Boards). Everything properly wired?

MKuhl.1
Associate II

Hey!

I want to use the LAN8742A on a STM32F437VI.

Unfortunately it doesn't work as intended. I have the suspicion that sth is not properly wired because the Ethernet LED's doesn't light up after powering up. The initialization via LWIP doesn't work properly as well. It doesn't get an IP Address. I would be gladful if someone can have a look.

0690X00000D8FCUQA3.png

0690X00000D8FPnQAN.png

2 REPLIES 2
Piranha
Chief II

LED1 at connector is wired backwards. Both LEDs have 70 ohm series resistors, which seems like a copy-paste error from a typical 270 ohm values. If it is intended, the value should be 68 ohms. Take a note, that at 2,5 V LED forward voltage, the LED current will be very close to the 12 mA maximum. But the most suspicious is nRST with a single capacitor and without any pull-up resistor or reset circuit.

NRST on MCU looks even more suspicious...

Also take a look on this: https://community.st.com/s/question/0D50X0000BOtfhnSQB/how-to-make-ethernet-and-lwip-working-on-stm32

MKuhl.1
Associate II

Thank you for your answer! I've added the pull-up resistors, the capacitor, the faulty resistors and the polarity of the LED, and i've still no activity on the LED's after powering up. So there seems to be another wiring issue and i still can't find it. :downcast_face_with_sweat:

Thank you for your answer, i'll have a look at it after the LAN8742 works properly .