How does CB3S UART module communicate with CMS32L051 MCU in Noname Reclosing Protector?

Question 1

They use TuyaMCU over UART. Energy data often arrives as a compound RAW blob named TAC2121C_VCP: two bytes each for voltage, current, and power with scaling. “They are using compound format… scaled by 10.” OpenBeken already supports this mapping. [Elektroda, p.kaczmarek2, post #21742261]

Answer

They use TuyaMCU over UART. Energy data often arrives as a compound RAW blob named TAC2121C_VCP: two bytes each for voltage, current, and power with scaling. “They are using compound format… scaled by 10.” OpenBeken already supports this mapping. [Elektroda, p.kaczmarek2, post #21742261]

Question 2

The thread does not fix a baud, but two points matter: power the whole device to see traffic, and treat the UART as potentially at mains potential. Use the shared analyzer tool workflow and keep isolation in mind while probing. [Elektroda, p.kaczmarek2, post #21742115]

Answer

The thread does not fix a baud, but two points matter: power the whole device to see traffic, and treat the UART as potentially at mains potential. Use the shared analyzer tool workflow and keep isolation in mind while probing. [Elektroda, p.kaczmarek2, post #21742115]

Question 3

TuyaMCU is the serial protocol that a Tuya Wi‑Fi module (CB3S) uses to exchange dpIDs with the product MCU. In this device, it carries metering and control frames between CB3S and CMS32L051. [Elektroda, p.kaczmarek2, post #21742115]

Answer

TuyaMCU is the serial protocol that a Tuya Wi‑Fi module (CB3S) uses to exchange dpIDs with the product MCU. In this device, it carries metering and control frames between CB3S and CMS32L051. [Elektroda, p.kaczmarek2, post #21742115]

Question 4

Use the TAC2121C_VCP layout: two bytes per value. Compute V = value/10, I = value/1000, P = value. For example, bytes 0x09 0x1C → 2332 → 233.2 V. Map these to OBK channels or first-of-type handlers. [Elektroda, p.kaczmarek2, post #21742261]

Answer

Use the TAC2121C_VCP layout: two bytes per value. Compute V = value/10, I = value/1000, P = value. For example, bytes 0x09 0x1C → 2332 → 233.2 V. Map these to OBK channels or first-of-type handlers. [Elektroda, p.kaczmarek2, post #21742261]

Question 5

In the posted capture, dpID 6 contains a RAW array whose first two bytes decode to 233.2 V after scaling. Current and power follow as adjacent two‑byte fields. [Elektroda, p.kaczmarek2, post #21742261]

Answer

In the posted capture, dpID 6 contains a RAW array whose first two bytes decode to 233.2 V after scaling. Current and power follow as adjacent two‑byte fields. [Elektroda, p.kaczmarek2, post #21742261]

Question 6

It’s device‑specific. First, capture how the Tuya app or MCU performs the reset, if available. Then send the same dpID command from OBK. Without a native function, you may try writing the dpID value (e.g., set to 0) carefully. [Elektroda, p.kaczmarek2, post #21744236]

Answer

It’s device‑specific. First, capture how the Tuya app or MCU performs the reset, if available. Then send the same dpID command from OBK. Without a native function, you may try writing the dpID value (e.g., set to 0) carefully. [Elektroda, p.kaczmarek2, post #21744236]

Question 7

Yes. Since the app lacks this function, capture UART when performing related actions, identify the dpID for energy total, and craft the matching OBK command. A member suggested testing a dpID write to 0 for reset. [Elektroda, p.kaczmarek2, post #21744257]

Answer

Yes. Since the app lacks this function, capture UART when performing related actions, identify the dpID for energy total, and craft the matching OBK command. A member suggested testing a dpID write to 0 for reset. [Elektroda, p.kaczmarek2, post #21744257]

Question 8

No, not directly. Power supplies may be non‑isolated, and mains potential can appear on UART lines. Power the entire device for traffic, and use isolation and safe practices. “Very dangerous” was emphasized in the thread. [Elektroda, p.kaczmarek2, post #21742115]

Answer

No, not directly. Power supplies may be non‑isolated, and mains potential can appear on UART lines. Power the entire device for traffic, and use isolation and safe practices. “Very dangerous” was emphasized in the thread. [Elektroda, p.kaczmarek2, post #21742115]

Question 9

Disconnect the module’s UART from the mainboard before flashing. Shared rails or active MCU lines can block the bootloader. This was a key fix suggested in the thread. [Elektroda, p.kaczmarek2, post #21744236]

Answer

Disconnect the module’s UART from the mainboard before flashing. Shared rails or active MCU lines can block the bootloader. This was a key fix suggested in the thread. [Elektroda, p.kaczmarek2, post #21744236]

Question 10

Use four lines: RX, TX, GND, and VCC from the interconnect between the mainboard and the CB3S. The original poster confirmed these pins and attempted multiple adapters using them. [Elektroda, xopkep, post #21745189]

Answer

Use four lines: RX, TX, GND, and VCC from the interconnect between the mainboard and the CB3S. The original poster confirmed these pins and attempted multiple adapters using them. [Elektroda, xopkep, post #21745189]

Question 11

Yes. Keep leads short and ensure stable power. The OP used wires under 15 cm and tried both adapter power and an external 3 V supply while troubleshooting. [Elektroda, xopkep, post #21745246]

Answer

Yes. Keep leads short and ensure stable power. The OP used wires under 15 cm and tried both adapter power and an external 3 V supply while troubleshooting. [Elektroda, xopkep, post #21745246]

Question 12

Direct‑soldering to RX/TX on the CB3S is a valid troubleshooting step when headers or interposers fail. A community member recommended it in the thread. [Elektroda, divadiow, post #21750253]

Answer

Direct‑soldering to RX/TX on the CB3S is a valid troubleshooting step when headers or interposers fail. A community member recommended it in the thread. [Elektroda, divadiow, post #21750253]

Question 13

In this board, the back side had no mask or traces according to the OP. That reduces hidden pull‑ups or vias interfering with boot. Still confirm on your PCB revision. [Elektroda, xopkep, post #21751602]

Answer

In this board, the back side had no mask or traces according to the OP. That reduces hidden pull‑ups or vias interfering with boot. Still confirm on your PCB revision. [Elektroda, xopkep, post #21751602]

Question 14

OpenBeken (OBK) is community firmware for Tuya modules. The maintainer suggested backing up the 2 MB flash, then flashing OBK to parse the metering blobs and expose MQTT control without the cloud. [Elektroda, p.kaczmarek2, post #21742115]

Answer

OpenBeken (OBK) is community firmware for Tuya modules. The maintainer suggested backing up the 2 MB flash, then flashing OBK to parse the metering blobs and expose MQTT control without the cloud. [Elektroda, p.kaczmarek2, post #21742115]

Question 15

Yes. OBK handles DP_TYPE_RAW_TAC2121C_VCP with per‑field scaling and channel mapping. This format is “known and works in OBK well,” per the maintainer. [Elektroda, p.kaczmarek2, post #21742261]

Answer

Yes. OBK handles DP_TYPE_RAW_TAC2121C_VCP with per‑field scaling and channel mapping. This format is “known and works in OBK well,” per the maintainer. [Elektroda, p.kaczmarek2, post #21742261]

Question 16

Answer

Make a full 2 MB flash backup of the CB3S.
Disconnect UART lines to the mainboard and power the module safely.
Flash OBK, then map dpIDs and test metering decode. [Elektroda, p.kaczmarek2, post #21742115]

How does CB3S UART module communicate with CMS32L051 MCU in Noname Reclosing Protector?

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