FAQ
TL;DR: 2 MB Tuya RDA5981 modules exist; “GPIO2 is used as log tx.” This FAQ distills BL3335‑P/RDA5981 teardown notes, SDK status, and dump tips. For modders migrating generic 15W RGBW bulbs off proprietary stacks. [Elektroda, insmod, post #21634746]
Why it matters: It shows how to identify the module, grab a boot log, and safely dump firmware when documentation is scarce.
Quick Facts
- SoC/module ID: Broadlink BL3335‑P uses RDA5981AM, confirmed by teardown and linked docs. [Elektroda, Altirix, post #21434407]
- Flash sizes seen: Tuya WRD2L/WRD3S modules are 2 MB and rare/pricey. [Elektroda, insmod, post #21634746]
- HLK‑M50 often maps as 1 MB; wrong dump bases can create a repeated 2044 KB image. [Elektroda, divadiow, post #21479530]
- SDK status: Public RDA5981 SDKs are old (Mbed OS 5.1.5 v1.3.5); no FreeRTOS noted. [Elektroda, insmod, post #21434414]
- Tuya modules: GPIO2 is designated as the UART log TX. [Tuya WRD3L Datasheet]
What chip is inside the Broadlink BL3335‑P smart bulb module?
A teardown shows the RF can covers an RDA5981AM Wi‑Fi SoC. The carrier PCB is marked BR3335, and the assembled module is sold as BL3335‑P. Photos in the thread reveal the die marking after peeling the shield. This identification aligns the bulb with the RDA5981 software ecosystem rather than ESP‑class parts. [Elektroda, Altirix, post #21434019]
Where can I find documentation for BL3335‑P and RDA5981AM?
Start with the FCC user manual for Broadlink BL3335‑P and the RDA5981AM datasheet. Both links are collected in the thread for quick access. The docs help with pinout, regulatory details, and SoC capabilities, which are essential for logging and firmware work. [Elektroda, Altirix, post #21434407]
Is there open-source firmware support for RDA5981 (OpenBeken/Tasmota/ESPHome)?
Active, mainstream support is not available. Builders have replaced the module with an ESP‑based board in similar bulbs due to the lack of open stacks targeting RDA5981. The thread opener invites contributors to attempt a port if interested. [Elektroda, Altirix, post #21434019]
How do I capture a boot log from an RDA5981 bulb or module?
Use a 3.3 V USB‑to‑serial (an Arduino in pass‑through mode works) and connect to RX/TX. Power the board at 3.3 V from a stable source. Open a terminal and reset the device to catch the early boot prints. [Elektroda, Altirix, post #21434407]
Which pin outputs logs on Tuya RDA5981 modules like WRD2L/WRD3S?
Tuya’s datasheet specifies GPIO2 as the log UART transmitter. Route your USB‑to‑serial RX to GPIO2 and common ground, then try standard baud rates. If silent, logs may be disabled in that build. [Tuya WRD3L Datasheet]
What RDA5981 SDKs exist, and are they viable today?
Public SDKs are dated Mbed OS 5.1.5 branches, and FreeRTOS isn’t provided. As one contributor puts it, “the sdks i’ve seen are very old.” Expect missing modern tooling and limited RTOS choices without vendor updates. [Elektroda, insmod, post #21434414]
How can I dump HLK‑M50 (RDA5981) firmware without duplication artifacts?
Use correct start address and 1 MB length to include the bootloader. The RDA Dump tool’s default vendor settings produce a 2044 KB file with repeated content on HLK‑M50. Adjust offsets to avoid mirrored dumps. [Elektroda, divadiow, post #21479530]
Why do I see no boot log or AP on an HLK‑M50 module?
One tester observed no UART output at any baud and no AP, only a brief power spike. That behavior suggests the image disables logs and soft‑AP or the device waits for external triggers. Verify power integrity and logging pins. [Elektroda, divadiow, post #21479538]
Are Tuya RDA5981 modules still available, and which models exist?
Yes, but they’re rare and expensive. Identified 2 MB variants include WRD2L, TYWRD2S, and TYWRD3S. The same source also lists other interesting Wi‑Fi/BLE modules stocked by the seller, but not RDA5981 alternatives at similar cost. [Elektroda, insmod, post #21634746]
Any useful tools or repos for working with RDA5981 images?
Check hfeasy for utilities and the RDA Dump tool used with Hi‑Flying modules. The thread includes sample dumps, boot strings, and notes on correcting dump bases to avoid duplicated images. [Elektroda, divadiow, post #21479530]
Can desoldering the module help identify GPIOs and signals?
Yes. If documentation is thin, remove the can or the module and inspect the underside for silkscreened GPIO labels. This is a practical way to map UART and control lines before wiring. [Elektroda, p.kaczmarek2, post #21434400]
Is anyone porting OpenBeken to RDA5981 right now?
A maintainer expressed interest but is prioritizing XR806 porting first. That places any RDA5981 work in a queue without a public timeline. Community test hardware and logs would help when development starts. [Elektroda, p.kaczmarek2, post #21434400]
What’s inside the generic 15W RGBW B22 bulb using BL3335‑P?
It’s an unbranded bulb, likely from AliExpress, carrying a Broadlink BL3335‑P module with an RDA5981AM under the RF can. Prior art shows people replacing the control board with ESP boards due to software support gaps. [Elektroda, Altirix, post #21434019]
Do boot strings reveal anything about the firmware base?
Captured strings include “airkiss‑2.0.0‑25360 (Dec 17 2015) ... ARM Cortex‑M3” and a build timestamp from December 2017. Those indicate legacy Broadlink stacks and toolchains, aligning with the older SDK landscape. [Elektroda, divadiow, post #21479530]
Where can I browse an RDA5981 SDK repository snapshot?
A GitHub mirror collects RDA5981 SDK material, including Mbed OS 5.1.5 based trees. It’s a starting point for analysis, though not a modern upstream. [Elektroda, divadiow, post #21434436]
