---
title: "Firmware WIZ750SRv142.bin does not work (no ethernet comms); file size is suspiciously small"
url: "https://maker.wiznet.io/forum/15660"
markdown_url: "https://maker.wiznet.io/forum/15660/md"
type: "Forum topic"
category: "Serial-to-Ethernet & ConfigTool"
author: "buddye"
created: "2025-03-24T21:40:08+09:00"
last_activity: "2025-03-28T14:23:45+09:00"
language: "en"
tags: ["WIZ750SR"]
views: 5
replies: 1
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# Firmware WIZ750SRv142.bin does not work (no ethernet comms); file size is suspiciously small

## Question

Asked by buddye on 2025-03-24 in Serial-to-Ethernet & ConfigTool.

My WIZ750SR-232 came with firmware 1.3.3, and I configured and used the device. I wanted to use the web server for configuration, so I upgraded firmware to the latest stable 1.4.2 .

After this, the device would not connect over the Ethernet. Also no comm LED.

I jumpered APP_BOOT for recovery, and installed firmware 1.4.1 . This worked fine.

The file size of WIZ750SRV142.bin is 17.6KB. Considering the previous release sizes are around 57KB, this file seems too small.

## Replies

### Reply 1 by TheoIm, 2025-03-28

#### **You probably installed the firmware only for the APP area. Since version 1.4.2 has a slightly different BOOT area, you need to install the full firmware.** First, Download "[WIZ750SR-1XXv142_incl_boot.bin](https://github.com/Wiznet/WIZ750SR/releases/download/v1.4.2/WIZ750SR-1XXv142_incl_boot.bin)"

#### [ISP TOOL DOWNLOAD](https://docs.wiznet.io/Product/Open-Source-Hardware/surf5/getting-started/flashing-surf5) ISP Tool Steps (following the numbers)

**Open**

Select the correct Serial Port and Baud Rate

Click the **Open** button to connect (①)

In **Step 2 - Erase**, check **Erase All Code Memory** (②)

In **Step 5**, browse and select the full firmware binary file (③)

Click the **Start All Steps** button to download the firmware (④)

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Source: https://maker.wiznet.io/forum/15660