Exploring Cozylife DS-1321AL Smart Switch with Bouffalo Labs BL602 Module DT-BL02

In my never ending pursuit to collect everything I have obtained one of these neutral/no neutral Bouffalo Labs BL602-based smart switches. It's a single channel Cozylife DS-1321AL.


https://www.aliexpress.com/item/1005006150931509.html

Model: WiFi Switch Module
Input: AC100-240V 50/60Hz
Current: 10A
LED: Max 400W/Gang
Operation temp: -10℃-+40℃
Case temp:Tc: +80℃ (Max)
Dims (LxWxH):47.3x20x47.3 mm

Inside is a module I have not had or seen before. It has 1 mention on Elektroda in a post from @Zain00 and one from @Zhekos555 here.

The DT-BL02 looks to have something to do with Cozylife but the XT-BL02, which is referenced on the RF shield, is by Shenzhen Xiaoteng Technology Co. Datasheet attached.

https://cozylife.app/product/zh/hardware/wifi/dt-bl02.html




Some general pics first.



and with the module soldered up to the USB-TTL adaptor, the log out was captured:



and with D8 pulled high with a 10k resistor in circuit the factory firmware was dumped using BLDevCube 1.8.9, attached.

OpenBeken was flashed and booted as expected. The GPIO doctor led to the discovery the below assignment. Made even easier with the limited number of GPIOs exposed on the module.

"14": "Btn;1",
"20": "Rel;1",
"21": "WifiLED;0"

However! There is not continuity from P14 to the button contacts and the button does not work as expected. Using Btn_n we get this constantly in the logs



So maybe this is an ADC_Btn? Perhaps IO14 having ADC_2 function gives credence to this. This has no effect though and there is no adcbutton driver present in BL602 release.

OBK template



https://github.com/OpenBekenIOT/webapp/pull/133

Thank you for another interesting research. Regarding IO 14, how does it work in GPIO doctor or with dInput? Does it recognize both high and low state? Do you have to set just dInput, or maybe dInput_pullDown (or whatever it was called)?

well, with the bulb off (connected to output of relay) setting P14 to dinput closes the relay and the bulb comes on. Reverse that by changing P14 to dinput_n and the bulb will go off again.

I've tried dInput_NoPullUp and dInputNoPullUp_n also, but these have no effect on the relay

pushing the physical button does not toggle the relay open/closed with any assignment

Those no-neutral switches are indeed constructed in a very interesting manner. I wonder what is the purpose of those two NP3095 on the board?

I've been drawing a schematic of no-neutral wall light switch once. It was interesting:
https://www.elektroda.pl/rtvforum/topic3793509.html