--- title: "WIZ750SR-100 Configuration Issue with Firmware 1.4.x" url: "https://maker.wiznet.io/forum/16113" markdown_url: "https://maker.wiznet.io/forum/16113/md" type: "Forum topic" category: "Serial-to-Ethernet & ConfigTool" author: "LukasF" created: "2026-07-06T17:33:38+09:00" last_activity: "2026-07-22T09:45:10+09:00" language: "en" tags: ["WIZ750SR"] views: 6 replies: 5 source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)" --- # WIZ750SR-100 Configuration Issue with Firmware 1.4.x ## Question Asked by LukasF on 2026-07-06 in Serial-to-Ethernet & ConfigTool. Hello, I have been using the WIZ750SR-100 for several years, and everything works correctly with firmware versions earlier than 1.3.3. The latest batch of boards came with firmware version 1.4.2 (I also tested version 1.4.5). As soon as I use the configuration tool (v1.6.2.3) to modify the settings, the board stops working (no longer discover-able or ping-able) and the blue LED no longer turns on. I have attached the configuration file that I am using. Thank you for your support. Best regards, Lukas Attachments: - [WIZCONF.cfg](https://maker.wiznet.io/forum/getAttach.asp?aidx=392) ## Replies ### Reply 1 by Aimee0, 2026-07-07 Hello We have reviewed the configuration file you provided and would like to clarify a few points to help us reproduce the issue. 1) Your current network settings are: - Local IP: 172.25.3.1 - Subnet Mask: 255.248.0.0 (/13) - Remote Host: 172.24.3.1 With a /13 subnet mask, both IP addresses are considered to be on the same subnet. Could you please confirm that this is the intended network configuration? 2) Did exactly the same configuration work correctly with firmware v1.3.3 (or earlier), without any modifications? 3) After saving the configuration with v1.4.2 or v1.4.5: - Does the device reboot? - Does the Ethernet Link LED remain on? - Is the device still unreachable even after a Factory Reset? 4) Could you also let us know: - Whether these are brand-new boards shipped with firmware v1.4.x, or boards that were upgraded from an older firmware. - The IP address and subnet mask of the PC used for configuration. This information will help us reproduce the issue and investigate whether it is related to the firmware or the network configuration. Best regards, ### Reply 2 by LukasF, 2026-07-07 (in reply to reply 1) Hi, thanks for the fast answer! Here the requested information: 1. Yes 2. Yes 3. a) I do not know if the device made a reboot. 3. b) LED LD4 (green) and LD1 (red) still on. LD2 (blue) NOT on. 3. c) I do not know yet how to make a factory reset without being able to discover the device. I tried to connect the BOOT pin with ground, but no changes in LED pattern, and still not able to discover the device. 4. brand new boards that came with 1.4.2 The host PC has several network adapters / IP addresses, I selected: 172.20.0.165/16 I did try to configure another board, this time **I just changed "Operation Mode" from "TCP server" to "UDP"** and the device is now unreachable and the blue LED is off. ![](https://gcdnb.pbrd.co/images/7b-fqjB-J7Ge.jpg) ### Reply 3 by LukasF, 2026-07-09 Hi, Here the requested information: 1. Yes 2. Yes 3. a) I do not know if the device made a reboot. 3. b) LED LD4 (green) and LD1 (red) still on. LD2 (blue) NOT on. 3. c) I do not know yet how to make a factory reset without being able to discover the device. I tried to connect the BOOT pin with ground, but no changes in LED pattern, and still not able to discover the device. 4. brand new boards that came with 1.4.2 The host PC has several network adapters / IP addresses, I selected: 172.20.0.165/16 I did try to configure another board, this time **I just changed "Operation Mode" from "TCP server" to "UDP"** and the device is now unreachable and the blue LED is off. ![](https://gcdnb.pbrd.co/images/7b-fqjB-J7Ge.jpg) ### Reply 4 by LukasF, 2026-07-13 Please propose a solution to this problem as soon as possible, as it is time-sensitive for us. Thank you. ### Reply 5 by Aimee0, 2026-07-22 (in reply to reply 4) Hello, Apologize for the delayed response. To help us provide faster support, we would appreciate it if you could send the results of the following tests to **aimee@wiznet.io**. - You mentioned that the issue occurs even when only the **Operation Mode** is changed. Could you please check whether the same issue also occurs when **no settings are changed** and you simply click the **Apply** button or the **Factory** button? - Could you also download and test the previous version of the Configuration Tool (v1.5.8) from the link below and let us know whether the same issue occurs? Please send us the test results by email, or let us know your email address. We will review them as quickly as possible and provide further assistance. Thank you. --- Source: https://maker.wiznet.io/forum/16113