Sometimes IOS or other devices can interrupt WiFi signal and thus interrupt the OTA firmware upgrade. Then the device no longer transmits WiFi signal and OTA upgrade is not possible. And only thing left is to upgrade via USB cable. This way of upgrading the firmware is possible on Ispindel or relay devices.
For this procedure, you need a USB cable to connect Wemos (or another controller) to your computer. Then you need some kind of Flasher to upload and a Driver for your version of Wemos.
It all depends on the system you are using on your computer. We will update this page with new information over time.
For Windows https://github.com/nodemcu/nodemcu-flasher
Wemos D1 mini driver Or Wemos D1 mini pro (4MB) driver For Win or Mac https://www.wemos.cc/en/latest/ch340_driver.html
It depends on where your computer recognizes your hardware and assigns it a PORT
Select the port where the wemos are located (Picture1). If the port is incorrect the upload will not be possible, so change it to correct later.
Select the firmware.bin file from your computer (Pic 2)
Set the settings as in Figure 3
Where to connect USB in relay?
You must open the relay. For this you need a flat-blade screwdriver or solid nails 🙂 Carefully open the lid and remove the Wemos board from the slot. You plug the USB cable into it. Then select the correct settings in the Flasher and click on the Flash button.