And yes, EWL-B04 has BL602L20 inside.
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Oh wow, first one I’ve seen for a B04 module.
So it looks like you need to pry the metal shield after all to confirm it
You should add that info to elektroda
As for me, there is nothing to do with the shield.
The difference between the B04 modules with ESP8255 and BL602 is easily visible. The second one has a side window in the shield near 20-th contacts. And more, it has a line of resistors and capacitors just behind the antenna. And there is nothing like that for ESP8255.
By the way, the window can be seen on the squayor78’s photos.
Hi folks,
@squayor78 i have the same board and i find out a how to flash it:
I split the post beacause site don’t allow to post more than 1 pics or link
How it start:
Initially i unsolder the little board and i discover the pin map under the board:
After that i put it back on main board and wire up again the programmer
open a terminal on COM at 2000000 baud rate and the chip give me some helpful information about the pin settings:
Reading the dts file...
And the GPIO config is :
cfg->wifi_led = 17
cfg->all_on_off = 4
cfg->relay0 = 14
cfg->relay1 = 3
cfg->relay2 = 22
cfg->relay3 = 20
cfg->key0 = 21
cfg->key1 = 0
cfg->key2 = 1
cfg->key3 = 12
cfg.led_status = 0
cfg->led_status = 0
PT2 - Googling
thanks to @ybatuto that exposed the chip under the shell i decided to search more info and i found a guide https://www.elektroda.com/rtvforum/topic3889041.html that explain how to flash that chip and i notice it use productor flash utility called Bouffalo Lab Dev Cube
You can download it here: https://dev.bouffalolab.com/download
In that thread it refer to a tasmota/esphome like proget https://github.com/openshwprojects/OpenBK7231T_App/releases that is compatible with this chip (search for BL602 UART Flash)
Let’s flash it!
To program the chip you have to connect 3.3v RX TX GND and BOOT whit 10k resistor
Now using the BLDevCube.exe flasher use IOT tab and select 2MB partition and OpenKB bin file and flash it (do not select Chip Erase!).
After the flash is complete disconnect the resistor, unplug the programmer an power it, if all goes fine you can find the wifi ap, connect to it and set up the pin you need
Be dumb like me
If for some reason it not work (or maibe you are dump as i am and select Chip Erase) you have to add boot2 in the parameters:
Hope this can be helpfoul for someone 
I’m sorry for multiple post by i’m new user, so moderator be kind of me 
Actually ESPHome also works on a wide range of non-ESP based devices like beken or realtek. The mention BK7231T is also fully supported: 
Often it is possible to install esphome without opening or adding serial to the device with the help of cloudcutter 
I had already broken a sonoff, I had obviously burned something between TX and RX, even if with ewelink it still works. On the second sonoff instead I managed to get to the new firmware screen, entering from an IP address that was not 192.168.4.1. I entered the parameters of my wifi, and I was no longer able to see it… To try to solve it I also clicked on ‘erase’… how do I go back?
update: I finally did it! For instructions follow the posts on the other forum (elektroda.com)