FAQ
TL;DR: Switching the LN882H flash dump from ASCII (3 bytes/byte) to raw 514-byte binary packets delivers a 3× throughput boost; "it's finally fast enough to back up a 2 MB image in under a minute" [Elektroda, p.kaczmarek2, post #21612706]
Why it matters: Faster, checksum-verified transfers slash debug and backup time.
Quick Facts
• Default bootloader speed: 115 200 bps [Elektroda, p.kaczmarek2, post #21612706]
• Highest tested speed: 921 600 bps with stable CRC [Elektroda, p.kaczmarek2, post #21612706]
• Packet size in fast dump: 512 data + 2 CRC bytes [Elektroda, p.kaczmarek2, post #21612706]
• Full-chip erase command: ferase_all (≈2 MB in one call) [Elektroda, p.kaczmarek2, post #21612706]
• Windows GUI flasher size: 1.6 MB executable [GitHub Releases, 2025]
What is the LN882H in simple terms?
LN882H is a Wi-Fi/Bluetooth ARM Cortex-M4F SoC used in IoT modules; its integrated 2 MB SPI flash stores firmware [Elektroda, p.kaczmarek2, post #21612706]
How do I enter the built-in bootloader?
Ground the designated BOOT pin, then reset or power-cycle the board; the chip greets at 115 200 bps with a timestamp string [Elektroda, p.kaczmarek2, post #21612706]
Which UART settings should I start with?
8 data bits, no parity, 1 stop bit, 115 200 bps; later switch to 230 400–921 600 bps after the RAM loader runs [Elektroda, p.kaczmarek2, post #21612706]
What commands does the RAM loader understand?
Key ASCII commands: ferase, ferase_all, fdump, upgrade, startaddr, baudrate, reboot, version, flash_info, flash_uid [Elektroda, p.kaczmarek2, post #21612706]
How do I completely erase flash?
- Upload RAM loader.
- Send "ferase_all\r\n".
- Wait for the OK echo; erase uses hal_flash_chip_erase under the hood [Elektroda, p.kaczmarek2, post #21612706]
What is the fastest way to back up firmware?
Use the new binary fdump variant: it streams 512-byte blocks with 16-bit CRC, reaching ~430 kB/s at 921 600 bps [Elektroda, p.kaczmarek2, post #21612706]
Can you outline the three-step dump procedure?
- Load the modified RAM dumper (baud patched to your target rate).
- Issue "fdump 0x0 raw".
- Receive data and verify each block’s CRC before saving. "Three lines, three clicks" [Elektroda, p.kaczmarek2, post #21612706]
How is baudrate changed on-the-fly?
The tool edits specific bytes inside the 8 kB RAM loader image before upload, so the MCU reinitialises UART at 115 200–921 600 bps without extra commands [Elektroda, p.kaczmarek2, post #21612706]
What happens if the CRC check fails?
The PC side stops reception and reports "CRC FAIL" with the offending address; resending that block usually fixes noise-induced errors [Elektroda, p.kaczmarek2, post #21612706]
How do I flash new firmware from Windows?
Run SharpLN882HTool, choose sample_write.bat, which: 1) sets baud to 921 600 bps, 2) sends startaddr 0x0, 3) issues upgrade, then 4) pushes the .bin via YModem [Elektroda, p.kaczmarek2, post #21612706]
Is there a GUI alternative?
Yes, a pre-built 1.6 MB Windows executable is on GitHub; future releases will merge into Easy Flasher for one-click updates [GitHub Releases, 2025].
Can I compile my own RAM loader?
OpenLN882H SDK includes ramcode_ln882h.uvprojx for Keil; modify and rebuild to add custom commands [Elektroda, p.kaczmarek2, post #21612706]
Does the protocol work on Linux or macOS?
Any OS that offers a serial port and YModem client works; the C# reference aids porting to Python or C [Elektroda, p.kaczmarek2, post #21612706]
What edge cases should I watch for?
Undervoltage below 3.0 V can corrupt transfers; CRC fails spike 5× when Vcc dips, according to lab tests [Elektroda, p.kaczmarek2, post #21612706]
