USB Serial Adapter on Windows 10 for Sonoff (is this the right forum?)

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Joined:Thu May 31, 2018 8:36 pm
USB Serial Adapter on Windows 10 for Sonoff (is this the right forum?)

Post by autefrum » Thu May 31, 2018 8:55 pm

I bought one of these to flash my Sonoff Basic firmware. ... xBdcUjRDIU

However, I can't see it in Windows 10 Home 64 bit Device Manager.

My ultimate goal is to get Microsoft Visual Code seeing this port and uploading Tasmota firmware, but I am getting an error message "ERROR: Failed to open COM3" (or COM5 or what ever it is set to) in VS Code.

I set my Baud rate to 115200 in the device manager and my upload config file (upload_speed = 115200)

I tried following the instructions ... xBes0jRDIU which say Windows 10 needs no driver installation, and my Device Manager had one device under "Ports" but I don't think it was this USB Serial Adapter as when I changed the port from COM3 to COM5, and changed my COM port in my config file to match, it did not make any difference.

I have downloaded the driver files from ... and manually installed two drivers:
Freetronics 16U2 USB (COM3)
Freetronics 8U2 USB (COM4)
and can now see them both "This device cannot start. (Code 10). The specified request is not a valid operation for the target device." messages.
Both show the yellow diamond exclamation mark.

The usb serial device is powered up when I plug it into my PC, and I have connected to to the Sonoff Basic, which is responding with a blinking LED so I know it is powered up and running. However I have not seen any evidence the board is getting anything other than power from the PC.

I could not find this device in any of the forums, so I posted in this generic one. Happy for anyone to redirect me to a more suitable place.

Which of the two Freetronics driver is best (16U2 vs 8U2)? What other port settings need to be changed? (eg data bits, parity);

Thanks in advance!

Freetronics Staff
Freetronics Staff
Joined:Thu Jul 14, 2016 2:41 am

Re: USB Serial Adapter on Windows 10 for Sonoff (is this the right forum?)

Post by danieldewaard » Mon Jul 23, 2018 5:05 am


Thanks for getting in touch with us. Sorry about the slow reply. Are you still having issues with your Serial Adapter?

You shouldn't need to install any drivers, however it is possible that existing USB devices are interfering with the adapter. When you plug in the device it should be almost immediately recognized by windows 10 (which will install a driver for you). It will appear in the "Bluetooth and Other Devices" menu as a "USB Serial Device".

If you are still having any issues, uninstall the drivers you have installed, unplug other USB devices, restart your device and try again.


Joined:Thu May 31, 2018 8:36 pm

Re: USB Serial Adapter on Windows 10 for Sonoff (is this the right forum?)

Post by autefrum » Wed Oct 03, 2018 9:37 pm

I got this working - the hardware on my windows 10 shows up as:

Freetronics 16U2 USB

I use your hardware to connect my PC to a Sonoff Basic and use Microsoft Visual Studio Code to upload a bin file.
The port settings in the upload command in Visual Studio Code show up as
--- Miniterm on COM5 115200,8,N,1 ---

However (there is always a however), in Windows Command Prompt I would like to be able to upload also, so I issue commands:

Code: Select all

mode COM5 BAUD=115200 PARITY=n DATA=8

Status for device COM5:
    Baud:            115200
    Parity:          None
    Data Bits:       8
    Stop Bits:       1
    Timeout:         OFF
    XON/XOFF:        OFF
    CTS handshaking: OFF
    DSR handshaking: OFF
    DSR sensitivity: OFF
    DTR circuit:     OFF
    RTS circuit:     ON

copy firmware.bin \\.\COM5
and the freetronic's 'activity' led flashes for a while, and the dos prompt never returns to a prompt - so I don't know if it finishes.

I think it works, but I would like to know how to get confirmation once the file has finished copying.

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