I am new to Arduiino and just following the instruction in the plug and make kit.
All was well until one day it just would not connect. The LED matrix no longer shows ant attempt to connect to the cloud. USB link fails even though it revognises tge board is there. I get one green LED only. If i do a reset it flashes yellow.
I have tried all self help and ESP flash.
Stillnot working
Is that PWR/power?
A small number of flashes (three?), or continuous flashing?
Thanks, the Green is the "ON" LED and the yellow flash is the "TX" LED, about 10 seconds between flashes. Sometimes I can get to the wifi attempting to connect symbols on the matrix, but it hangs on a cloud symbol moving left/right with an intermittent flashing yellow LED. I am about to do a full uninstall of IDE and attempt to install core.
I have a new R4 and the same issue has recurred after set up. What is going on?
Please, post these instructions.
Things that need to be known...
How are you powering the Uno R4 (I assume USB cable, but could be other)?
Is there a "sleep" timer on your USB or computer (laptops usually have a "sleep" time to preserve battery charge... disable this when the laptop uses commercial power)?
Thank you again. I am using USB, good quality C port and also tried B. Install was originall using Arduino cloid, Add board vua USB. Things are worse now. Fails to always register. Furmware updater starts and then drops. Yellow flashing LED or green On only. Confused
Perhaps the USB port does not supply enough power for the Wi-Fi to function. Do you have an ultra-thin laptop?
Ordinary Dell.
The Uno worked for a few days, so all a bit odd.
It sounds like something is going to sleep... like the USB or network connection... or something on-board the Uno R4. Contact Arduino. They may have seen this problem before.
I am tending to second that, although, if you are sure that the USB cable is good then perhaps this might be worth a try:
Perhaps it got overwritten or corrupted somehow?
I will try the EDP flash again.
I cant find Arduino support, where is it?
Found it, ignore me
Hi, I think I'm struggling with a similar problem. Where you able to find a solution in the end? If so, what did you do?
Hi @jacob-b22. Please provide a detailed description of the problem you are encountering. Once we are sure we have a good understanding of your situation, we'll try to help you find a solution.
Hi @ptillisch, I've made a bit of progress since my last post. Mainly, I'm sure that I have to restore the USB connectivity using espflash since my board is not being recognised correctly when I connect it to my computer. I tried following the instructions at this link: (https://support.arduino.cc/hc/en-us/articles/16379769332892-Restore-the-USB-connectivity-firmware-on-UNO-R4-WiFi-with-espflash) given by arduino. However, I run into a checksum error which I'm unsure how to resolve. Here's the full process in my command window for further context:
C:\Users\jacob\Downloads\unor4wifi-update-windows>powershell
Windows PowerShell 5.1
Copyright (C) Microsoft Corporation. All rights reserved.
Install the latest PowerShell for new features and improvements! https://aka.ms/PSWindows
PS C:\Users\jacob\Downloads\unor4wifi-update-windows> bin\espflash write-bin -b 115200 0x0 (Get-Item .\firmware\UNOR4-WIFI-S3-*.bin).FullName
[2026-07-11T08:49:38Z INFO ] 🚀 A new version of espflash is available: v4.5.0
✔ Use serial port 'COM5' - USB Serial Device (COM5)? · yes
✔ Remember this serial port for future use? · no
[2026-07-11T08:49:43Z INFO ] Serial port: 'COM5'
[2026-07-11T08:49:43Z INFO ] Connecting...
[2026-07-11T08:49:43Z INFO ] Using flash stub
Chip type: esp32s3 (revision v0.2)
Crystal frequency: 40MHz
Flash size: 8MB
Features: WiFi, BLE
MAC address: 64:e8:33:68:ad:58
Error: x The bootloader returned an error
|-> Error while running FlashDeflateData command
`-> Bad data checksum
type or paste code here
Thanks for the clarification. I am able to reproduce the "Bad data checksum" error you encountered, and have submitted a formal report to the developers on your behalf:
The workaround will be to flash the previous firmware version: 0.5.2. After flashing that firmware to recover your board to a normal operational state, you can then use one of the alternative mechanisms to update the firmware to the modern version 0.6.0. I'll provide instructions you can follow to do that:
A. Flash Bridge Firmware Version 0.5.2
- Disconnect the USB cable of the UNO R4 WiFi board from your computer.
- Use a jumper wire to connect these two pins ("DOWNLOAD" and "GND") on the 2x3 male header that is near the USB socket on the UNO R4 WiFi board:
📷
Arduino - CC BY-SA 4.0 (cropped)
- Connect the UNO R4 WiFi board to your computer with a USB cable.
- Click the following link to open the release page for version 0.5.2 of the firmware in your web browser:
https://github.com/arduino/uno-r4-wifi-usb-bridge/releases/tag/0.5.2 - Click the "unor4wifi-update-windows.zip" download link under the "Assets" section of the release page:
- Wait for the download to finish.
- Extract the downloaded file.
- Start Windows "File Explorer".
- Open the
unor4wifi-update-windowsfolder that was created when you extracted the downloadedunor4wifi-update-windows.zipfile at the previous step in the instructions. - In the folder listing of the
unor4wifi-update-windowsfolder, hold the Shift key while clicking the right hand button on the mouse.
A context menu will open. - Select "Open PowerShell window here" from the menu.
Windows PowerShell will now open. - Type the following command in the PowerShell window:
bin\espflash write-bin -b 115200 0x0 (Get-Item .\firmware\UNOR4-WIFI-S3-*.bin).FullName - Press the Enter key.
- The PowerShell window might now show a list of the serial ports present on your computer.
For example:
If so, use the ↓ key on your keyboard to select the port of the UNO R4 WiFi board from the list, and then press the Enter key.Start flashing firmware [2023-07-11T06:39:09Z INFO ] Detected 2 serial ports [2023-07-11T06:39:09Z INFO ] Ports which match a known common dev board are highlighted [2023-07-11T06:39:09Z INFO ] Please select a port ❯ COM1 COM42- USB Serial Device (COM42) - The terminal window will now show the following prompt:
Press the N key on your keyboard.? Remember this serial port for future use? (y/n) › - The flashing process should now start. Wait for it to finish, as indicated by output that looks something like this:
Chip type: esp32s3 (revision v0.1) Crystal frequency: 40MHz Flash size: 8MB Features: WiFi, BLE MAC address: dc:54:75:c4:c6:54 [00:00:15] [========================================] 826/826 0x0 - Disconnect the USB cable of the UNO R4 WiFi board from your computer.
It is essential to perform this step. - Disconnect the jumper wire you added at step (2) of the instructions.
- Connect the UNO R4 WiFi board to your computer with the USB cable again.
B. Update Bridge Firmware to 0.6.0
You can now use one of the standard methods to update the firmware on an UNO R4 WiFi board that is in the normal operational state. This will allow you to update the board to using the latest firmware version 0.6.0.
Those methods are described here:
Please let us know if you have any problems or questions while following those instructions.
Hi again, I've just tried this workaround and unfortunately I'm still getting the same error. The only way I deviated from your instructions is that I don't have an option to open the power shell window directly from the file explorer. Instead, I open the command window and enter powershell before running the command you gave me. Here's my entire command window again if its helpful, but I'll keep looking for another workaround anyway.
C:\Users\jacob\Downloads\unor4wifi-update-windows>powershell
Windows PowerShell 5.1
Copyright (C) Microsoft Corporation. All rights reserved.
Install the latest PowerShell for new features and improvements! https://aka.ms/PSWindows
PS C:\Users\jacob\Downloads\unor4wifi-update-windows> bin\espflash write-bin -b 115200 0x0 (Get-Item .\firmware\UNOR4-WIFI-S3-*.bin).FullName
[2026-07-12T15:53:36Z INFO ] 🚀 A new version of espflash is available: v4.5.0
✔ Use serial port 'COM5' - USB Serial Device (COM5)? · yes
✔ Remember this serial port for future use? · no
[2026-07-12T15:53:38Z INFO ] Serial port: 'COM5'
[2026-07-12T15:53:38Z INFO ] Connecting...
[2026-07-12T15:53:39Z INFO ] Using flash stub
Chip type: esp32s3 (revision v0.2)
Crystal frequency: 40MHz
Flash size: 8MB
Features: WiFi, BLE
MAC address: 64:e8:33:68:ad:58
Error: x The bootloader returned an error
|-> Error while running FlashDeflateData command
`-> Bad data checksum
PS C:\Users\jacob\Downloads\unor4wifi-update-windows>
I did some more investigation and found that the correlation I thought I identified between the firmware version and the error was not actually real. I have now identified the cause of the problem as a tool named serial-discovery, which is used by Arduino IDE, Arduino Cloud Agent, and Arduino App Lab.
If you have any of those programs running on your computer, please exit them and then try updating the firmware once again, following the standard recovery procedure described here:
You don't need to worry about the modified procedure for flashing the 0.5.2 firmware I described in my previous reply.
Hopefully the firmware flashing will now complete successfully and will restore your board to a fully functional state.
Hi again, I've now uninstalled everything you mentioned just to be extra sure and tried running the command again. Initially this gave me a new error which you can see below. In an attempt to resolve this I tried changing the baud rate as was suggested to me by a member of staff in the support system. Since neither of these rates worked and since I was occasionally getting a timeout error I tried running the command at a baud rate of 921600 which actually allowed the command to fully execute however this also came with a warning that this baud rate may cause issues and, after reinstalling the arduino IDE, I have been unable to update the firmware and furthermore, the board appears to still not be recognised properly. I'm now worried I may have made the problem worse by executing the command at too high of a baud rate since the RX LED is now a steady amber even when I am updating the firmware. Is this still resolvable? Thanks again for all your help so far, I'm sorry I haven't been able to reproduce your success yet.
C:\Users\jacob\Downloads\unor4wifi-update-windows>powershell
Windows PowerShell 5.1
Copyright (C) Microsoft Corporation. All rights reserved.
Install the latest PowerShell for new features and improvements! https://aka.ms/PSWindows
PS C:\Users\jacob\Downloads\unor4wifi-update-windows> bin\espflash write-bin -b 115200 0x0 (Get-Item .\firmware\UNOR4-WIFI-S3-*.bin).FullName
[2026-07-17T21:47:02Z INFO ] 🚀 A new version of espflash is available: v4.5.0
✔ Use serial port 'COM5' - USB Serial Device (COM5)? · yes
✔ Remember this serial port for future use? · no
[2026-07-17T21:47:05Z INFO ] Serial port: 'COM5'
[2026-07-17T21:47:05Z INFO ] Connecting...
[2026-07-17T21:47:05Z INFO ] Using flash stub
Error: x The bootloader returned an error
|-> Error while running MemData command
`-> Other
PS C:\Users\jacob\Downloads\unor4wifi-update-windows> bin\espflash write-bin -b 57600 0x0 (Get-Item .\firmware\UNOR4-WIFI-S3-*.bin).FullName
[2026-07-17T21:47:58Z INFO ] 🚀 A new version of espflash is available: v4.5.0
✔ Use serial port 'COM5' - USB Serial Device (COM5)? · yes
✔ Remember this serial port for future use? · no
[2026-07-17T21:48:01Z INFO ] Serial port: 'COM5'
[2026-07-17T21:48:01Z INFO ] Connecting...
[2026-07-17T21:48:01Z INFO ] Using flash stub
Chip type: esp32s3 (revision v0.2)
Crystal frequency: 40MHz
Flash size: 8MB
Features: WiFi, BLE
MAC address: 64:e8:33:68:ad:58
Error: x The bootloader returned an error
|-> Error while running FlashDeflateData command
`-> Bad data checksum
PS C:\Users\jacob\Downloads\unor4wifi-update-windows> bin\espflash write-bin -b 38400 0x0 (Get-Item .\firmware\UNOR4-WIFI-S3-*.bin).FullName
[2026-07-17T21:48:27Z INFO ] 🚀 A new version of espflash is available: v4.5.0
✔ Use serial port 'COM5' - USB Serial Device (COM5)? · yes
✔ Remember this serial port for future use? · no
[2026-07-17T21:48:29Z INFO ] Serial port: 'COM5'
[2026-07-17T21:48:29Z INFO ] Connecting...
[2026-07-17T21:48:30Z INFO ] Using flash stub
Chip type: esp32s3 (revision v0.2)
Crystal frequency: 40MHz
Flash size: 8MB
Features: WiFi, BLE
MAC address: 64:e8:33:68:ad:58
Error: espflash::timeout
x Error while connecting to device
`-> Timeout while running FlashDeflateData command
PS C:\Users\jacob\Downloads\unor4wifi-update-windows> bin\espflash write-bin -b 38400 0x0 (Get-Item .\firmware\UNOR4-WIFI-S3-*.bin).FullName
[2026-07-17T21:48:55Z INFO ] 🚀 A new version of espflash is available: v4.5.0
✔ Use serial port 'COM5' - USB Serial Device (COM5)? · yes
✔ Remember this serial port for future use? · no
[2026-07-17T21:48:58Z INFO ] Serial port: 'COM5'
[2026-07-17T21:48:58Z INFO ] Connecting...
[2026-07-17T21:48:58Z INFO ] Using flash stub
Chip type: esp32s3 (revision v0.2)
Crystal frequency: 40MHz
Flash size: 8MB
Features: WiFi, BLE
MAC address: 64:e8:33:68:ad:58
Error: x The bootloader returned an error
|-> Error while running FlashDeflateData command
`-> Bad data checksum
PS C:\Users\jacob\Downloads\unor4wifi-update-windows> bin\espflash write-bin -b 38400 0x0 (Get-Item .\firmware\UNOR4-WIFI-S3-*.bin).FullName
[2026-07-17T21:49:22Z INFO ] 🚀 A new version of espflash is available: v4.5.0
✔ Use serial port 'COM5' - USB Serial Device (COM5)? · yes
✔ Remember this serial port for future use? · no
[2026-07-17T21:49:24Z INFO ] Serial port: 'COM5'
[2026-07-17T21:49:24Z INFO ] Connecting...
[2026-07-17T21:49:24Z INFO ] Using flash stub
Chip type: esp32s3 (revision v0.2)
Crystal frequency: 40MHz
Flash size: 8MB
Features: WiFi, BLE
MAC address: 64:e8:33:68:ad:58
Error: x The bootloader returned an error
|-> Error while running FlashDeflateData command
`-> Bad data checksum
never mind, after trying this again today I was able to resolve this issue. I believe last time I may have accidentally left one file related to the Arduino IDE installed whilst performing the esp flash method. Regardless, thanks so much for all your help @ptillisch, I'm so grateful to be able to actually start using my arduino again.