Problem:
I run the ethernet example code with a Lan8720 chip and everything appears to be working correctly, there are no errors, the lights on the ethernet port are flashing, and the example executes successfully. The problem is that the ESP32 is not assigned an IP address.
Observations:
- This behavior is consistent across multiple build platforms, DHCP servers, and firmware versions
- I connected an oscilloscope to the EMAC clock and the 50 MHz clock seems to be working correctly
- I see data coming over the EMAC RX0 and EMAC RX1 pins
- I see no signal over the EMAC TX0 and TX1 pins
- When powered on the EMAC TX0 and TX1 pins are shorted, but when powered off they are not. This behavior is unique to the TX pins.
Configuration:
EMAC TX0 - GPIO 19
EMAC TX1 - GPIO 22
EMAC RX0 - GPIO 25
EMAX RX1 - GPIO 26
Comments:
From what I have observed and what I have read, I think there is some sort of dual pin assignment or flow control happening on the EMAC TX pins. The result is that not information is sent over these pins, the DHCP receives no response, and thus no IP address is assigned. This could be the case, but it is only a guess, and I am a little hazy on the specifics of this guess.
Any insight on this problem would be greatly appreciated.