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PTiha
PTiha
Associate III
July 23, 2020
Question

LwIP raw api with static IP and NUCLEO-F429ZI slow startup: It takes 15 seconds for the first ping.

  • July 23, 2020
  • 4 replies
  • 1510 views

Hello!

I created a standard LwIP NO-OS project with static IP. Everything works perfectly, but it takes ~ 15 seconds for the first PING response.

After that the ping times ~1.4 ms.

I tried what happens when I disconnect the Ethernet cable and then reconnect it.

It took another 15 seconds to re-establish the connection (the first ping response arrived).

The MCU core clock is 168 MHz. SysTick is 1ms.

Why can this be?

This topic has been closed for replies.

4 replies

Pavel A.
Pavel A.
July 23, 2020

This is likely because the example is set to use DHCP with lot of retries before falling back to a static address, and you don't have a DHCP server.

-- pa

PTiha
PTihaAuthor
Associate III
July 24, 2020

Hello,

It should not send DHCP requests because the DHCP module is disabled.

PTiha
PTihaAuthor
Associate III
July 24, 2020

In the meantime I watched the communication between the NUCLEO and my developer notebook with Wireshark.

There isn't any DHCP requests from the NUCLEO.

I don't know what he's doing for 15 seconds.

J.Strom
J.Strom
Visitor II
December 3, 2020

Hi PTiha,

Did you solve the problem? I have the same problem. After link is up there is a delay of several seconds, then it works as expected. Also with DHCP disabled.

Johan

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