the bulb

Cheap CCT tunable wifi smart bulb. Bought in Apr 2026 for ₹280 off Amazon.in, although it was manufactured in Oct 2023.

  • ESP8685-WROOM-04
  • 32-bit RISC V, 160MHz
  • 2MB flash (normal modules have 4MB)
  • BP5936 dual channel LED driver
  • BP2306, seems to be for the power supply

First time tinkering with a device that has a RISC-V processor.

As usual, my aim is to make it work fully locally with Home Assistant, no servers in China involved.

I opened it up, took out the board, soldered wires to the wifi module, and powered it with a 3.3V supply.

Stock firmware serial output

ESP-ROM:esp32c3-api1-20210207
ESP-ROM:esp32c3-api1-20210207
ESP-ROM:esp32c3-api1-20210207
Build:Feb  7 2021
rst:0xf (BROWNOUT_RST),boot:0x9 (SPI_FAST_FLASH_BOOT)
SPIWP:0xee
mode:DIO, clock div:1
load:0x3fcd6100,len:0xc84
load:0x403ce000,len:0x714
load:0x403d0000,len:0x275c
entry 0x403ce000
ESP-ROM:esp32c3-api1-20210207
Build:Feb  7 2021
rst:0xf (BROWNOUT_RST),boot:0x9 (SPI_FAST_FLASH_BOOT)
SPIWP:0xee
mode:DIO, clock div:1
load:0x3fcd6100,len:0xc84
load:0x403ce000,len:0x714
load:0x403d0000,len:0x275c
entry 0x403ce000
ESP-ROM:esp32c3-api1-20210207
Build:Feb  7 2021
rst:0xf (BROWNOUT_RST),boot:0x9 (SPI_FAST_FLASH_BOOT)
SPIWP:0xee
mode:DIO, clock div:1
load:0x3fcd6100,len:0xc84
load:0x403ce000,len:0x714
load:0x403d0000,len:0x275c
entry 0x403ce000
I (38) cpu_start: Pro cpu up.
I (50) cpu_start: Pro cpu start user code
I (50) cpu_start: cpu freq: 160000000
I (50) cpu_start: Application information:
I (50) cpu_start: Project name:     smartbulb
I (54) cpu_start: App version:      eef5c8b-dirty
I (58) cpu_start: Compile time:     Jan 26 2023 11:46:49
I (63) cpu_start: ELF file SHA256:  94d0c934ef33a9a1...
I (68) cpu_start: ESP-IDF:          v4.3
I (72) heap_init: Initializing. RAM available for dynamic allocation:
I (78) heap_init: At 3FC96700 len 00029900 (166 KiB): DRAM
I (83) heap_init: At 3FCC0000 len 0001F060 (124 KiB): STACK/DRAM
I (89) heap_init: At 50000010 len 00001FE0 (7 KiB): RTCRAM
I (95) spi_flash: detected chip: generic
I (98) spi_flash: flash io: dio
I (101) sleep: Configure to isolate all GPIO pins in sleep state
I (107) sleep: Enable automatic switching of GPIO sleep configuration
I (113) cpu_start: Starting scheduler.

Stock firmware esptool output

esptool.js
Serial port WebSerial VendorID 0x1a86 ProductID 0x7523
Connecting...
Detecting chip type... ESP32-C3
Chip Revision: 3
Chip is ESP8685 (QFN28) (revision v0.3)
Features: Wi-Fi,BLE,Embedded Flash 2MB (TT)
Crystal is 40MHz
MAC: 58:cf:79:74:3d:58
Uploading stub...
Running stub...
Stub running...
Flash ID: 1560eb

(continued in part 2)