FAQ
TL;DR: 142 kB of free heap are shown at boot [Elektroda, ferbulous, post #21303798]; “LOG really is just the log output” [Elektroda, divadiow, post #21303825] CKW04/SV6166F shares Andes-N10 core and can be flashed through UART or USB once GPIO 13 (nRESET) is held low. Why it matters: knowing pins and tools lets you swap Tuya firmware for OpenBeken in under 10 minutes.
Quick Facts
• MCU core: Andes-N10 RISC, 160–240 MHz (typical) [ICOMM datasheet].
• Default boot baud: 115 200 bps; alternative 9 600 & 921 600 bps supported [Elektroda, divadiow, post #21301615]
• On-chip RAM: 256 kB; free heap at boot ≈ 142 kB [Elektroda, ferbulous, post #21303798]
• Flash pads: GPIO3, GPIO4 = TX/RX; GPIO13 = nRESET; HSDP/HSDM = USB D+/D– [Elektroda, divadiow, post #21478503]
• Partial SDK (SV6166/6006) in Hi-Flying LPD100 package, 280 MB download [Elektroda, insmod, post #21478212]
Is the CKW04 really the same as the ICOMM SV6166F?
Pad layout, boot strings ("start_sniffer_mode") and SDK files labelled SV6166F match the CKW04 board, so the chips are pin-compatible [Elektroda, divadiow, post #21311332]
What UART pins give boot logs?
Connect only LOG pad (TX) to your USB-TTL RX plus common ground. 115 200 bps shows the full bootloader; 9 600 bps reveals “factory?” strings on TXD1/GPIO7 [Elektroda, ferbulous, #21303798; #21479961].
Which baud rates should I try if 115 200 is silent?
Test 115 200 first, then 9 600, 74 880, and 921 600 bps—these covered every report in the thread [Elektroda, divadiow, post #21301615]
How do I enter download (flash) mode?
- Hold GPIO13 (nRESET) low.
- Keep GPIO0 high (normal boot).
- Power-cycle; the bootloader prints “press 'm' to enter boot menu” and waits 1 s for XMODEM upload [Elektroda, divadiow, #21478503; #21303798].
Can I flash via USB instead of UART?
Yes. The CKW04 exposes HSDP/HSDM pads; the Hi-Flying HF-LPD1x0 manual shows the same SoC using USB DFU with SecureCRT/XMODEM [Elektroda, p.kaczmarek2, post #21520722]
Is there an open SDK?
A partial 280 MB SDK for the SSV6006/SV6166 target ships with Hi-Flying LPD100 tools; it contains GCC toolchain, headers and sample drivers [Elektroda, insmod, post #21478212]
Does the chip support 5 GHz Wi-Fi?
SV6266F variant adds 5 GHz; SV6166F/CKW04 stays 2.4 GHz only [Elektroda, insmod, post #21478385]
What’s the risk of bricking during flashing?
Edge case: pulling wrong GPIOs low makes the CPU boot normally, so firmware upload never starts—device continues pairing loop but remains recoverable [Elektroda, divadiow, post #21478503]
How much memory is available for OpenBeken?
Bootloader shows 142 096 bytes free heap after reserving stack and radio buffers [Elektroda, ferbulous, post #21303798]
Which tools can send the XMODEM image?
SecureCRT, Tera Term, or the vendor’s HF Programmer all support 128-byte XMODEM blocks required by the boot ROM [HF-LPD100 Manual].
Can I capture more verbose logs during pairing?
Yes. Initiate Tuya-app pairing; additional Wi-Fi scan, FFS cloud, and key-exchange messages appear, roughly doubling log length [Elektroda, divadiow, post #21311332]
What file names does the bootloader expect?
ota.bin and ota_info.bin are searched first; if absent it waits for XMODEM upload and prints “can not find ota.bin, plz use xmodem” [Elektroda, ferbulous, post #21303798]
How big can the firmware image be?
The SPIFFS reports 257 free blocks × 4 kB = ~1 MB for application code [Elektroda, ferbulous, post #21303798]
Why does my log stop after Wi-Fi init?
Low 3.3 V rail in the live mains board can reset UART; power the module from a bench supply when logging [Expert field note, divadiow, #21312117].
How long does the bootloader wait for XMODEM?
Exactly 1 second; press 'm' quickly or script it, or it jumps to normal firmware [Elektroda, ferbulous, post #21303798]
Any cost advantage over ESP8266?
Modules appear in Sonoff Micro-CFH retailing €6; a comparable ESP8285 board is ~€8, so 25 % cheaper [AliExpress listing, 2024].