---
title: "[From QnA] WIZ108SR RS485"
url: "https://maker.wiznet.io/forum/9497"
markdown_url: "https://maker.wiznet.io/forum/9497/md"
type: "Forum topic"
category: "Serial-to-Ethernet & ConfigTool"
author: "jameskim"
created: "2013-09-09T00:17:51+09:00"
last_activity: "2017-05-04T08:29:53+09:00"
language: "en"
views: 995
replies: 4
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# [From QnA] WIZ108SR RS485

## Question

Asked by jameskim on 2013-09-09 in Serial-to-Ethernet & ConfigTool.

I am using WIZ108 as RS485 Interface. Communication is working well. I can also receive messages.
I cannot send any message. The 485_SEL Pin is not connected, but message is not transmittet via RS485 Pins TRXD+ and TRXD-. Message is only transmitted on TXD+ and TXD-. It seems, that Pin 485_Sel is not switched by the system. Is there a special setup needed?

## Replies

### Reply 1 by jameskim, 2013-09-09

Dear customer,

Please confirm the 485sel pin level when you send the data.
When you send the data, 485sel is switching.(high->low)
Thanks,
WIZnet

### Reply 2 by jameskim, 2013-09-09

485_SEL Pin is not connected and always Low. When I manually connect to +3.3 and transmit Data, the Data is send out on TXD+/TXD-.

### Reply 3 by jameskim, 2013-09-09

Dear customer,

Please check the pin 2 of U2:SP3485EN.
Please confirm the pin2 level when you send the data.
When you send the data, pin2 is switching.(high->low)
thanks,
WIZnet

### Reply 4 by jameskim, 2013-09-09

Pin2 is always low.
For my understanding: Pin2 should switch to high during sending of data and then be low again.

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Source: https://maker.wiznet.io/forum/9497