FAQ
TL;DR: Use 2,000,000 baud to read BL602 boot logs; “2000000 baud from same tx as flashing.” This FAQ maps pins, variants, and flashing steps for RMC021/SM‑028_V1.3. [Elektroda, divadiow, post #21602985]
Why it matters: This helps tinkerers flash OpenBeken/OpenBL, decode logs, and map GPIOs on BL602‑based RMC021 plugs without guesswork.
Quick Facts
- Platform: RMC021 uses SM‑028_V1.3 (BL602); shared template maps Button=P22 and Relay=P2. [Elektroda, C4ve, post #21224333]
- Stock firmware seen: FWSWES‑BLSWP1‑SWP1‑BL602L_v1.1.1; PSM=16 KB, ENV=8 KB. [Elektroda, divadiow, post #21440109]
- Serial logging: boot output at 2,000,000 baud on the same TX used for flashing. [Elektroda, divadiow, post #21602985]
- Power stage: 3 V relay with BP2525 in 3 V config, saving a 3.3 V regulator. [Elektroda, miegapele, post #21440150]
- Variants exist, including a red‑PCB version similar to another documented unit. [Elektroda, divadiow, post #21228756]
How do I get a readable BL602 boot log on this smart plug?
Set the serial to 2,000,000 baud and use the same TX pin used for flashing. Open your terminal, power the board, and watch the boot sequence. You should see readable output immediately if the UART is wired correctly. [Elektroda, divadiow, post #21602985]
Why is my serial output garbled or blank even if flashing succeeds?
Insufficient power from a USB‑TTL adapter can corrupt output or cause resets when Wi‑Fi initializes. Provide a stronger 3.3 V supply. Expect plain text until Wi‑Fi starts, even with a weak source. Fix power first, then recheck logs at the correct baud. [Elektroda, divadiow, post #21603147]
Which terminal should I use in Bouffalo tools, and what do I click?
Use BLDevCube’s Terminal tab and open your COM port. The dropdown selections do not matter for viewing logs. Output appears in the lower console when baud and wiring are correct. [Elektroda, divadiow, post #21603190]
What UART pins do I need on SM‑028_V1.3 to flash firmware?
Solder wires to the module’s 3.3 V, GND, RX, TX, and BT pads. Connect a CH340 USB‑TTL to these, then use Bouffalo Lab Dev Cube over UART to flash. This setup was used successfully. [Elektroda, C4ve, post #21224333]
What OpenBeken/OpenBL pin template worked for one RMC021 unit?
Shared mapping: Relay=P2, BL0937CF1=P3, BL0937CF=P14, LED_n=P20, BL0937SEL=P21, Button=P22. Use this as a baseline. Adjust if your hardware revision differs. [Elektroda, C4ve, post #21224333]
My button doesn’t respond after flashing—how do I find its GPIO quickly?
In OBK, assign Btn to unassigned GPIOs, one at a time, and press the device button. Watch the web log for button or long‑press entries. Multiple spurious entries often indicate BL0937 metering lines. [Elektroda, divadiow, post #21604272]
Is the button ever on P4 instead of P22?
Yes. One owner found the button on P4 after flashing OBK on an SM‑028_V1.3 unit. Verify on your device before finalizing templates. [Elektroda, blacksun2, post #21604683]
How do I map BL0937 CF, CF1, and SEL to BL602 pins?
Trace the three metering lines from the BL0937 to module pads with a multimeter. Assign BL0937CF/CF1/SEL to those GPIOs in OBK and validate readings. “GPIO Dr can help greatly.” Limited SM‑028_V1.3 pads constrain options. [Elektroda, divadiow, post #21603525]
What firmware version ships on these, and what does the boot log show?
Observed stock firmware: FWSWES‑BLSWP1‑SWP1‑BL602L_v1.1.1. Boot logs report EasyFlash V4.0.99, PSM partition size 16 KB, and ENV area 8 KB. “EasyFlash V4.0.99 is initialize success.” [Elektroda, divadiow, post #21440109]
Are there multiple RMC021 hardware variants I should expect?
Yes. Several RMC021 variants exist, including a red‑PCB model similar to another documented socket. Check the OpenBeken device list for closest matches before configuring pins. [Elektroda, divadiow, post #21228756]
Is my BL602 an L10 or L20, and why does my backup seem small?
BL602L20 uses 2 MB flash; L10 uses 1 MB. If your chip is L20 but your backup is 1 MB, you likely dumped only half the flash. Re‑dump at the full capacity. [Elektroda, divadiow, post #21603525]
Can OpenBeken display the actual flash size on this device?
In this thread, users inferred flash size from the chip code (L10 vs L20) and backup length, not from an OBK field. Use those indicators to confirm capacity. [Elektroda, divadiow, post #21603525]
Will a CP2102 adapter work, and how should I power the board?
One user used a CP2102, feeding 5 V into a step‑down to 3.3 V. Their unit booted, joined Wi‑Fi, blinked blue, and replied to ping. Ensure a stable 3.3 V supply during logging. [Elektroda, blacksun2, post #21603162]
How do I flash OpenBeken/OpenBL over UART on the RMC021?
- Solder to SM‑028_V1.3 pads: 3.3 V, GND, RX, TX, BT.
- Connect a CH340 USB‑TTL and open Bouffalo Lab Dev Cube (UART).
- Flash the image, reboot, and continue configuration. [Elektroda, C4ve, post #21224333]
Which GPIOs drive the LED and relay in the shared template?
Relay uses P2, and the LED uses P20 (active‑low LED_n). Keep LED_n if your LED is inverted; otherwise test LED. [Elektroda, C4ve, post #21224333]
