Identifying GND Pin on LN882HKI Mini Smart Socket PCB for Reflashing

Question

I'm trying to reflash the socket, but I can't find the GND.

It looks very similar to this device: https://www.elektroda.com/rtvforum/topic4091325.html, but I don't have a GND pin.

Part Number: LN882HKI

UPD: The quartz crystal housing is connected to this contact, so I assume it's ground.
I plugged it into a power outlet and measured the voltage between the 3V3 and this contact with a multimeter. Yes, it is GND.
Sorry, I'm new to this.

p.kaczmarek2 · Accepted Answer

Yes, this is one of the methods. You can also check the ground side of electrolytic capacitors or of the power supply chip. Also, the large copper pour is often ground. Just make sure to verify your findings first, because there are sometimes cases where capacitor is connected in reverse or when pour is not GND. So it's better to double check.

Have you managed to take flash backup from the device? Did you flash it with new firmware, how it went?

max4elektroda · Accepted Answer

One reliable way is usually a known component. E.g. it looks like there's a power metering chip on the first picture in the lower left corner. Look up it's pin out and the GND reference should be clear. Another 50% chance (though I'd rather think it's 90%) is the button: one side is connected to the LN882H, the other is high or low (I've only seen it connected to GND for now). Usually one of the contacts of the plug (the ones plugged into an outlet) is connected to GND, too. So if you know one reference point, it's easy to find one which is good to access. But the metal housing of a quartz is also a good start... Taking a backup is good for our collection and to extract the usage of the pins. Last hint: it won't prevent some shorts and possible damage to the plug but reduce the possibility of an electric shock: if you have a power supply with some higher voltage you can try to power the complete plug with this. Some even work on 12V, most with an old laptop power supply of 19V. Recently I found an old 48V supply for a PoE powered device which works great. Since the plug is for AC, it doesn't matter where to connect + and -. While this voltage is no danger to life, it's still a much higher voltage than 3.3V which can damage your plug or a connected UART, ...

p.kaczmarek2 · Accepted Answer

Ah yes, I can see BL0937 there.

Block diagram of BL0937 in SOP8 package with labeled pins and internal functional blocks

The GND location for this chip is known.

By the way, an interesting observation - it's yet another no-LDO device. There is no 3.3V LDO on this board. It seems that BP2525 provides 3.3V directly. The relay used there is S3F-S-103DM model, which runs on 3V.

SANYOU SRD-S-112D relay with technical specifications and application list

divadiow · Accepted Answer

boot log from your backup file, for the record: Code: TextLog in, to see the code Code: JSONLog in, to see the code Added after 19 [minutes]:

p.kaczmarek2 · Accepted Answer

Thanks for the PR. So now we're getting to 817 devices. Not bad. I wonder how much did we have at the beggining of 2025? Or 2024.... we would need to look back and check, we'll then know how fast our list is growing.
https://openbekeniot.github.io/webapp/devicesList.html

vokamut · Answer

I soldered together a spider from an unused ESP8266 board and stainless steel wire. I have six of these sockets and don't have a soldering iron tip that thin. I successfully re-flashed it. I'm attaching a wiring circuitand the original firmware. Config: Code: text Expand Select all Copy to clipboard {   vendor: SmartLife,   bDetailed: 0,   name: Mini Smart Socket EU16/20A Wifi Smart Plug With Power Monitoring,   model: EU20A,   chip: LN882H,   board: on PCB,   flags: 1024,   keywords: [     LN882HKI,     BL0937,     socket,     BP2525   ],   pins: {     6: LED_n;0,     7: Btn;0,     19: Rel;0,     20: BL0937CF;0,     21: BL0937CF1;0,     22: BL0937SEL;0   },   command: setChannelLabel 0 \Toggle\,   image:    wiki:  }

vokamut · Answer

Can you tell me how to rename a switch from 0 to Switch in the socket firmware itself? Added after 19 [minutes]:

p.kaczmarek2 · Answer

you can use setChannelLabel in short startup command or autoexec.bat

vokamut · Answer

If this helps, here are 5 more firmware versions from other sockets:


{
  "uuid":"d50e43cd35a953c3",
  "psk_key":"null",
  "auth_key":"IqkJXEcEMG0MsYUiccvAdd1xUApkcTak",
  "ap_ssid":"SmartLife",
  "ap_passwd":"null",
  "7 rcs.activebt_hid":"null",
  "prod_test":"false",
  "fac_pin":"qsjrrszpjipdyjpy",
  "psk30_key":"null "
}

{
  "uuid":"15faa5dcfbe56bb1",
  "psk_key":"null",
  "auth_key":"6AmIK2gwS2S08sJl3SSp9a1mz88jXzgA",
  "ap_ssid":"SmartLife",
  "ap_passwd":"null",
  "7 rcs.activebt_hid":"null",
  "prod_test":"false",
  "fac_pin":"qsjrrszpjipdyjpy",
  "psk30_key":"null "
}
{
  "uuid":"ba947f5c297e95f6",
  "psk_key":"null",
  "auth_key":"XYxALTt3OgFzLfc6KtIn8JSqf9zMdgAw",
  "ap_ssid":"SmartLife",
  "ap_passwd":"null",
  "country_code":"null",
  "bt_mac":"null",
  "bt_hid":"null",
  "prod_test":"false",
  "fac_pin":"qsjrrszpjipdyjpy",
  "psk30_key":"null "
}

{
  "uuid":"b90c5975a049930d",
  "psk_key":"null",
  "auth_key":"C4KUqSD34HNF4iGj4L370bACEeomHXkI",
  "ap_ssid":"SmartLife",
  "ap_passwd":"null",
  "7 rcs.activebt_hid":"null",
  "prod_test":"false",
  "fac_pin":"qsjrrszpjipdyjpy",
  "psk30_key":"null "
}

Identifying GND Pin on LN882HKI Mini Smart Socket PCB for Reflashing

Post #1

Post #2

Post #3

Post #4

Post #5

Post #6

Post #7

Post #8

Post #9

Post #10

Didn't find an answer? Ask Artificial Intelligence

Topic summary