In this tutorial post, I describe how you can erase and flash an ESP32 module with a NMEA4WIFI BIN file without using the Arduino IDE. In some circumstances you may need to do this. I tried this method using Windows 10. I am not sure if you can use another OS. You need to download a tool from ExpressIf, the manufacturer of the ESP32. The tool is is available as a ZIP file called flash_download_tool_v3.8.7.zip that can be download from the ExpressIf or the Vela-Navega website. You need an USB data cable to connect the PC to the ESP32 module and take a note of the COM port that Windows attributes to the USB adapter. If your multiplexer is of the TH (Trough Hole) type you could remove the module from the multiplexer as the USB cable also supplies power to the module. After you download the flash_download_tool_v3.8.7.zip file, you unzip it and run the executable flash_download_tool_v3.8.7.exe. You may need to run this programme as an administrator. When the programme starts it will present a window where you should select ESP32 as the Chip Type and develop as the WorkMode. Then, when you press OK, you receive 2 windows - one with a black display running in the background and the ESP32 user interface running in the foreground
You should choose the parameters as shown in the picture and in particular choose your COM port number and the BAUD rate of 921600, at the bottom right corner. In my case the COM port number is 24. At this stage the green square shows IDLE. Pressing START in the line below, you get information about the ESP32 module as shown in the following picture. That means that the USB cable connection between the PC and the ESP32 module is working.
At this time, you SHOULD DO AN ERASE and wait until the tool finishes. In doing so, you erase all the contents of the ESP32 and will start with a blank ESP32.
Now I suggest you create a TEMP folder to place there the needed BIN files to flash the module. You will need 4 files. One file is the main file that you can download from the Binary Updates List. You also need 3 additional BIN files contained in the archive FlashBins.zip. Here are the 4 files placed in the folder C:/TEMP:
Now you have to specify these 4 files together with the addresses were the files will be uploaded. This is shown in the following picture. For example the file boot_app0.bin goes to address 0xe000. In the picture we show the final stage of the flash operation. Actually, when we press START the progress green bar increases to the right and when the process terminates the green square box shows FINISH.
If you had the module removed from the multiplexer PCB you need to reinsert it, respecting its original orientation. The multiplexer will run the uploaded firmware: in this case version 4.4!