---
title: "Module not starting correctlly"
url: "https://maker.wiznet.io/forum/13411"
markdown_url: "https://maker.wiznet.io/forum/13411/md"
type: "Forum topic"
category: "Ethernet Chips"
author: "johanan"
created: "2019-07-24T06:47:57+09:00"
last_activity: "2019-07-24T17:17:23+09:00"
language: "en"
views: 646
replies: 5
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# Module not starting correctlly

## Question

Asked by johanan on 2019-07-24 in Ethernet Chips.

I made a pcb with W5100S.
The software starts with DHCP discovery. the DHCP fail many trails, but then after a very long time, it seems to get an IP, and everything works well from this point on (fast and reliable TCP connection).
When I use the same software with W5100S module (WIZ810io) all is working well and DHCP discovery is normal ( < 10 seconds).
What could be the problem?

## Replies

### Reply 1 by Eugeny, 2019-07-24

Please provide

- circuit diagram of your design.

- Wireshark log from the PC pn the network between W5100s and DHCP server (or from DHCP server if it is able to run Wireshark).

- any differences in LED operation between your design and WIZnet module.

### Reply 2 by johanan, 2019-07-24 (in reply to reply 1)

Thanks.
Here is a link to the schematics.

[drive.google.com](https://drive.google.com/file/d/1s5b-r5Q3JUeXhzD1-QlEBPenYVAQOZNy/view?usp=sharing)

![](https://maker.wiznet.io/forum_uploads/wiznet/original/2X/c/c8f36ba7d515715d1cdd67dd8f2379b6b5a553f5.png)

### [WiznetModule.pdf](https://drive.google.com/file/d/1s5b-r5Q3JUeXhzD1-QlEBPenYVAQOZNy/view?usp=sharing)

Google Drive file.

I am not very familiar with wireshark, I am looking at it right now, will upload log later.
Let me know if something is wrong/missing from this design.
Also, I wonder if there are some grounding issues that can create such problems.
Johanan

### Reply 3 by johanan, 2019-07-24

I nailed it…
termination resistors on PHY connection were 49.9 K instead of 49.9 Ohm…
Makes a lot of difference.
Now all works OK.

### Reply 4 by Eugeny, 2019-07-24 (in reply to reply 3)

Great!
You are not the first one with this mistake, and not the last one ![:slight_smile:](https://emoji.discourse-cdn.com/twitter/slight_smile.png?v=12)

### Reply 5 by johanan, 2019-07-24

BTW, will it be OK if I replace the W5100S with the pin compatible W6100 on board? (hardware - I know the library need to change)
Thanks

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Source: https://maker.wiznet.io/forum/13411