title: STM32H7 LAN8742 LwIP only works fine after power-up, not after reset
body: <p>I have a weird problem on hand, I never saw it before.
  Yet, I'm still trying to pinpoint the problem.
  I have an STM32H753VIT and a LAN8742 ethernet controller connected to it.
  I run LwIP in NO-SYS mode.
  It only works fine after a cold power-up, but not after a hardware reset (button or ST-LINK probe).
  It runs a simple TCP echo server. If it runs, I can ping it, and it responds to a TCP client.</p>
  
  <p>But after a hardware reset, I no longer can ping it, and it does not respond as an echo server.
  I noticed the green (link) LED on the interface will remain off after the reset.</p>
  
  <p>I could see the LAN8742_Init function executes successful after a hardware reset, but it sees no longer RX data available in the function low_level_input.</p>
  
  <p>On a Nucleo-H743ZI, I run the same code, and this also works after a hardware reset.
  Note the code is only slightly different as pin mapping is slightly different.
  Code for well working Nucleo-H743ZI:
  <a href="https://github.com/bkht/Nucleo-H743ZI_LAN8742_LwIP_NO-SYS" rel="nofollow noreferrer">https://github.com/bkht/Nucleo-H743ZI_LAN8742_LwIP_NO-SYS</a>
  Code for strange behaving STM32H753VIT:
  <a href="https://github.com/bkht/STM32H753VIT_LAN8742_LwIP_NO-SYS" rel="nofollow noreferrer">https://github.com/bkht/STM32H753VIT_LAN8742_LwIP_NO-SYS</a></p>
  
  <p>The nRST of the MCU is connected to the nRST of the LAN8742A and a capacitor of 100nF is used to GND. I've a reset switch and I tried a Pull-up resistor, nut no luck.
  I have added a reset button, and this found that a longer hardware reset does not work either.</p>
  
  <p>I'm thinking in the direction of timing, or memory contents.
  Has anybody ever seen such start-up behavior?</p>