FAQ
TL;DR: 70 °C internal temperature was logged on stock settings, but drops to 32 °C after PowerSave 2; “LN882H flashing is very similar to ESP8266 flashing” [Elektroda, p.kaczmarek2, post #20923772] Use 115 200 baud and keep BOOT (A9) low for reliable uploads [Elektroda, voodoopt, post #20958664]
Why it matters: Correct wiring, speed and power rules prevent bricked modules and overheating.
Quick Facts
• Flash size: 2 MB NOR, dump script trimmed to 0x200000 bytes [Elektroda, divadiow, post #21284784]
• Stable upload speed: 115 200 baud; 2 Mbit/s often fails [Elektroda, voodoopt, post #20958664]
• BOOT=A9 must stay at GND from power-on until flashing ends [Elektroda, p.kaczmarek2, post #20905518]
• PowerSave 2 cuts idle current from ≈55 mA to 35 mA (-36 %) [Elektroda, max4elektroda, post #21064064]
• OTA bug fixed in releases ≥1.17.789; Firefox now works [Elektroda, divadiow, post #21332121]
1. What minimum hardware is required to flash an LN882H module?
- USB-to-UART adapter that outputs true 3 V3 (CH340 or CP2102 proven). 2. Solid 3 V3 supply ≥300 mA; many adapters sag. 3. Five leads: 3 V3, GND, RX, TX, BOOT (A9). 4. Optional: pogo pins or fine wires for in-circuit work [Elektroda, p.kaczmarek2, post #20905518]
2. Which pins go where?
• Module TX → UART RX
• Module RX → UART TX
• 3 V3 ↔ 3 V3
• GND ↔ GND
• A9 (BOOT) ↔ GND (keep low)
Any disconnect of A9 before power-cycle aborts flashing [Elektroda, p.kaczmarek2, post #20905518]
3. How do I enter download mode every time?
- Hold A9 at GND. 2. Remove and re-insert USB power to both UART and module. 3. Start flash command. After any failure repeat the full power cycle—soft reset is not enough [Elektroda, p.kaczmarek2, post #20933029]
4. Flash tool stops with “Fail. Error downloading file”. Fix?
Set baud to 115 200 bps; many CH340/FTDI clones error at 2 000 000 bps. Example: “Ok.” after lowering speed on COM21 [Elektroda, voodoopt, post #20958664]
5. Can I flash without desoldering the module?
Yes, if you can grip A9 and ensure RX/TX lines are not tied to buttons or capacitors. Cut the trace or lift parts if debouncing cap blocks UART [Elektroda, p.kaczmarek2, post #20923772]
6. Quick 3-step firmware backup before experimenting?
- python LN882H_Flash_Dumper.py COMx flashdump 2. Wait ~5 min for 2 MB readout. 3. Verify flashdump_flash.bin size == 2097152 bytes [Elektroda, divadiow, post #21284784]
7. Why does my device overheat to 70 °C idle?
LN882H runs full-power by default; logs showed 70 °C internal with relay OFF [Elektroda, Piorun2002, post #21055191] Enabling PowerSave 2 (“PowerSave 2”) cut temp to 32 °C and current by 36 % [Elektroda, Piorun2002, post #21055421]
8. How do I enable PowerSave automatically?
Add in Startup Command: backlog delay_s 5; PowerSave 2. From release 1.17.772 the firmware applies PowerSave after Wi-Fi connects, so no boot lock [Elektroda, max4elektroda, post #21064290]
9. Edge-case: BL0937 energy meter shows 125 V after PowerSave.
PowerSave disables the interrupt clock BL0937 needs. Keep PowerSave 0 on power-monitor plugs or voltage reading will be wrong [Elektroda, max4elektroda, post #21052031]
10. OTA upload crashes when I use Firefox. Work-around?
Firmware ≤1.17.772 overflowed a 4 kB buffer when the header and payload arrived in one TCP packet, often triggered by Firefox. Patched in 1.17.789 (PR #1441) [Elektroda, max4elektroda, post #21319958] Use Chrome or update firmware.
11. How can I reset a forgotten Web-UI password?
From 1.17.800 you can power-cycle, then enter 5 wrong logins within 3 min; firmware offers full config reset unless Flag 77 disables it [Elektroda, max4elektroda, post #21086964]
12. What smart-home devices ship with LN882H?
Documented examples: Cozylife LN-02 mini switch, WL2S relay board, GU10 RGB-CW bulb, LSPA9 plug [Elektroda, divadiow, post #21018533]
13. Linux/Mac flashing tool available?
Yes. Open-source LN882Loader (CLI) handles dump and flash on Linux/macOS; requires PySerial [stefanmandl, 2025].
14. Static IP option missing—bug?
Static IP not yet implemented; Wi-Fi init ignores provided IP struct. Needs update to wifi_init_sta() [Elektroda, p.kaczmarek2, post #20997185]
15. How do I change a duplicate MAC address?
mac write xx:xx:xx:xx:xx:xx works but device reboots with new IP. Verify the MAC is unique before saving [Elektroda, Advian1, post #20996463]
16. Quick How-To: flash in 3 steps
- Hold A9 → GND, power module.
- LN882H_CMD_Tool COMx download flash 115200 0x0 OpenLN882H_xxx.bin
- Power-cycle, release A9, connect to AP 192.168.4.1 and configure.
