LN882H modules can be flashed over UART with open-source Tasmota/Esphome-style firmware to free cloud-controlled devices and integrate them with Home Assistant.
Wire module TX, RX, GND, 3V3, and BOOT/GPIOA9 to ground, and keep GPIOA9 low throughout the entire flashing process.
Backup uses `python LN882H_Flash_Dumper.py COMx flashdump`, and the firmware flash command is `LN882H_CMD_Tool.exe COMx download flash 921000 0x0 flashimage.bin`.
After flashing, power-cycle the module, disconnect BOOT from ground, and open 192.168.4.1 to configure it like other OpenBeken/Tasmota-style devices.
A reliable external 3.3V supply is recommended because powering directly from the USB-to-UART adapter’s 3.3V pin may fail.
Merged, thank you!
The PowerSave actually also breaks BL0937 on other platforms, like on Beken, but in that case even PowerSave 1 breaks it. And as far as I know Tuya is also not using PowerSave on BL0937 devices. This is because BL0937 works by counting pulses with a GPIO interrupt...
Ok, so what's next for LN882H? Hm, isn't LittleFS still missing?
How is the LN882H name designated for MQTT?
In the configuration, I have entered different names than those broadcast in the 'Native', tasmota and hass modes.
Ok, so what's next for LN882H? Hm, isn't LittleFS still missing?
I made a new PR for this (PR #1191), which will fail for LN882H, because the littleFS files are missing in OpenLN882Hs CMakeList.txt
@p.kaczmarek2: I think I remember you mentioned, how to fix this with some git force command... Maybe you would be so nice to do this?
During my affords I struggled with some strange findings:
Even before the compiler reached my additions to the littlefs source the compilation was aborted.
E.g.: Simply defining LittleFS (#define ENABLE_LITTLEFS 1) for LN882H leads to a bunch of (misleading) errors, I couldn't really understand.
Mostly some (incorrect, from my point of view) complaints about conflicting types like the first error occuring:
And then in src/new_cfg.c, the defines from the included files where not present (here LFS_BLOCKS_DEFAULT_LEN was indicated "undefined"), so I had to do a nasty hack here:
uint32_t CFG_GetLFS_Size() {
#ifndef LFS_BLOCKS_DEFAULT_LEN // nasty hack. There is something strange with the includes of littlefs in conjunction with LN882H - this define is included in our_lfs.h but not there ?!?!?
#define LFS_BLOCKS_DEFAULT_LEN 0x8000
#endif
The last thing to mention is probably a size issue: the OTA image I flashed was not applied after a reboot.
So I reduced the size of the image by un-defining all the other drivers (but file size was way below the OTA partition size)???
But in the end, with all these hacks, I have successfully created a file which I could access after a reboot:
Thanks to git user @giedriuslt , I could resolve the strange compiler issues.
I turned out to be different type definitions for bool, so the conflicts were real
LFS compiles fine now, the lfs_tests1-3 succeeded and the contents of LFS where still present after several OTA updates...
Since the build needs including an aditional source file it will fail, until this modification is made in the OpenLN882H part.
But I can build an actual firmware later and attach it.
Added after 2 [hours] 13 [minutes]:
Here you are
Attachments:
OpenLN882H_dev_20240503_155700_OTA.bin(351.18 KB)
You must be logged in to download this attachment.
Good job @max4elektroda, but can you submit your changes to SDK as a PR?
max4elektroda wrote:
I made a new PR for this (PR #1191), which will fail for LN882H, because the littleFS files are missing in OpenLN882Hs CMakeList.txt
@p.kaczmarek2: I think I remember you mentioned, how to fix this with some git force command... Maybe you would be so nice to do this?
Works for me I tested auto switch off:
--------
// This aliased command will turn off relay on CH1 after 10 seconds
// addRepeatingEvent [IntervalSeconds][RepeatsOr-1][CommandToRun]
alias turn_off_after_time addRepeatingEvent 10 1 setChannel 1 0
// this will run the turn off command every time that CH1 becomes 1
addChangeHandler Channel1 == 1 turn_off_after_time
----------
I will do another build later, actualy I had test commands enabled, too.
Build (including test commands) used 654KB, the actual release is 610 KB.
So it should be ~40 KB
Added after 8 [minutes]:
W/o test commands size is 652KB, so LFS adds 42KB
But, to be honest, it's more than LFS, since also all this code for scripting is enabed, if LFS is present, which is not related to LFS itself...
Build on May 3 2024 15:57:10 version dev_20240503_155700
Something is wrong with this build - after 1-2 hours, ping works, but web management does not (I also use PowerSave 2)
I'm using it now Build on May 4 2024 15:20:53 version 1191_merge_eb591d9a473a
I turned off some test MQTT options (hass / tele discovery) and it seems to work well
Flag 27 - [HASS] Invoke HomeAssistant discovery on change to ip address, configuration
Flag 30 - [MQTT] Enable Tasmota TELE etc publishes (for ioBroker etc)
Yea I just noticed that, I am making LN882H dev board out of scrap and I was suprised to see that this particular pin is always high for me.
I almost got HD2015 display working.
✨ The discussion focuses on flashing LN882H modules with open-source firmware similar to Tasmota/Esphome, enabling cloud-free operation and integration with Home Assistant. Flashing requires a USB to UART converter with reliable 3.3V power supply, connecting module TX to UART RX, RX to TX, GND to GND, and 3.3V to 3.3V. Users report challenges including access to the BOOT pin, interference from board components on RX/TX lines, and the necessity of short wiring to ensure stable flashing. Various USB to UART converters (CH340, FT232RL, PL2303, CP2101) have differing success rates; CH340 and CP2101 are recommended over some FTDI and PL2303 adapters. Correct baud rate (115200) and running the flashing tool from non-system drives (e.g., D:) improve success. The LN882H_CMD_Tool is used for flashing and dumping firmware; flashing requires power cycling and keeping BOOT grounded during operations. Users successfully dumped firmware but often encountered "Fail. Error downloading file" during flashing, resolved by adjusting baud rate, shortening cables, and using compatible USB-UART adapters.
Power-saving features are under active development; enabling PowerSave mode reduces power consumption and device temperature but may cause WiFi connection issues in some firmware versions. PowerSave commands can be set via startup commands or command tool, with better effect when applied directly via command tool. Temperature monitoring shows LN882H devices run hot (up to 74°C) without load, improved by PowerSave mode. Integration with energy metering (BL0937) is affected by PowerSave due to interrupt handling. Static IP assignment is currently unimplemented in firmware. DHT sensor support is partially implemented; drivers require manual start commands, and pin mapping must be correct. NTP client requires manual driver start and supports server IP configuration via commands. Safe mode can be triggered by power cycling to reset device settings. Firmware and tools are evolving with ongoing commits addressing power management, filesystem (LittleFS), and device stability.
Overall, flashing LN882H modules demands careful hardware setup, compatible USB-UART adapters, correct flashing parameters, and power cycling. Firmware features like power saving, sensor support, and network configuration are improving but still have limitations. Community contributions and testing continue to enhance LN882H open-source firmware usability and integration. Generated by the language model.
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]
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]
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]
