---
title: "communication between atmega328p to w5100"
url: "https://maker.wiznet.io/forum/14835"
markdown_url: "https://maker.wiznet.io/forum/14835/md"
type: "Forum topic"
category: "Ethernet Chips"
author: "nitzanm"
created: "2023-03-19T15:48:06+09:00"
last_activity: "2023-03-21T14:48:09+09:00"
language: "en"
views: 305
replies: 7
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# communication between atmega328p to w5100

## Question

Asked by nitzanm on 2023-03-19 in Ethernet Chips.

Hello everyone,
I designed an electric circuit, the purpose of which is to read information from several sensors in the circuit, and I want to share the information from the sensors on the network.
The problem is that I connected the RJ-45 cable and there is no communication, and the LEDs do not flash.
What is the reason for this? Maybe the W5100 component needs to be initialized?

[![1](https://maker.wiznet.io/forum_uploads/wiznet/original/2X/7/79b37b7ff30fad6b35159c3afd623686c833a6a3.png) 11674×627 139 KB](https://maker.wiznet.io/forum_uploads/wiznet/original/2X/7/79b37b7ff30fad6b35159c3afd623686c833a6a3.png)

[![image](https://maker.wiznet.io/forum_uploads/wiznet/original/2X/9/93f8e4e6144c2a58a8bb2dfecf9dba8bfb8749a4.png) image856×546 35.3 KB](https://maker.wiznet.io/forum_uploads/wiznet/original/2X/9/93f8e4e6144c2a58a8bb2dfecf9dba8bfb8749a4.png)

## Replies

### Reply 1 by Eugeny, 2023-03-19

A number of reasons. First is you must operate RESET pin to properly reset chip on power on. Then may it happen you confused RJ-45 assembly pins? Then - does SPI communication work?

### Reply 2 by nitzanm, 2023-03-19

Hey,
Can you tell me what to do about the reset pin?
I didn’t connect well?
And regarding the rj-45 connector, I was not confused.
Is it necessary to do a certain initialization for the component? (some kind of burning)

### Reply 3 by Eugeny, 2023-03-20 (in reply to reply 2)

![](https://avatars.discourse-cdn.com/v4/letter/n/258eb7/48.png) nitzanm:

> Can you tell me what to do about the reset pin?
> I didn’t connect well?

You have reset pin not connected anywhere on the circuit diagram. I would recommend resetting the chip using MCU, according to the datasheet, or at least put RC reset circuit (at best with Schmitt trigger).

Eugeny:

> Then - does SPI communication work?

Did you check if it works even there’s no PHY connection indication?

### Reply 4 by nitzanm, 2023-03-20

I connected the reset pin of w5100 to reset pin of my MCU atmega328p…is still doesn’t working.
The spi communication is working.

### Reply 5 by Eugeny, 2023-03-20 (in reply to reply 4)

Ok, your PHY circuit is wrong. Please refer to the [W5100 hardware design guide](https://www.wiznet.io/wp-content/uploads/wiznethome/Chip/W5100/Hardware/w5100_hardware.zip) for proper circuit diagram.

### Reply 6 by nitzanm, 2023-03-20

Can you show me exactly where the mistake is?

### Reply 7 by Eugeny, 2023-03-21 (in reply to reply 6)

Compare your RX and TX design to the sample in WIZnet documentation. RD channel’s center of transformer.

---

Source: https://maker.wiznet.io/forum/14835