Bluetooth Mesh Serial Protocol

This topic describes the serial protocol that is used to implement serial communication between Tuya’s Bluetooth module and the third-party MCU. The following diagram shows how the two-way communication between the Bluetooth module and the cloud works.

Serial communication

Terms

Frame format

DP format

Serial protocol

Send heartbeats (0x00)

• After power-on, the module will send a heartbeat to the MCU every 300 ms. If the MCU correctly responds to a heartbeat, it indicates proper operation. After the first-time heartbeat communication, the module will send the MCU a command to get product information.

• The MCU can determine whether the module works properly by detecting heartbeats. If the module does not send heartbeats at regular intervals, the MCU can use the reset pin to reset the module.

• After getting the product information, the module will send a heartbeat every 10 seconds in the standard power mode.

• In the low power mode, the heartbeat communication will stop after a device joins a mesh network. After a restart, the Bluetooth module only sends the current network status to the MCU.

  Since the heartbeat communication stops in the low power mode, the module cannot detect whether the MCU has been restarted.

The module sends the following command.

The MCU returns the following command.

Get MCU information (0x01)

• Product key: 8-byte value assigned to each product for storing product information in the cloud.
• Product information: refers to the PID.

The module sends the following command.

The MCU returns the following command.

• Data format:

  1 to 8	9 to 13
  The PID.	A reserved field populated with the MCU version number. The module does not parse this field.

• For example, 55 AA 00 01 00 0D 66 74 62 38 78 32 78 30 31 2E 30 2E 30 C0, indicating the PID is ftb8x2x0 and the MCU version number is 1.0.0.

Send pairing state (0x03)

• The module sends this command to the MCU to notify its current pairing state. The valid values are 0x00 (unpaired) and 0x02 (paired).
• The module will send its current pairing state to the MCU after responding to the command 0x02.
• The module will send its current pairing state to the MCU if the state changes.

The module sends the following command.

The following block diagram shows how the module communicates with the MCU.

Reset the module (0x04)

The MCU sends this command to disconnect a module from a mesh network. This way, the module will be reset and become unpaired.

The MCU sends the following command.

For example, 55 aa 00 04 00 00 03

The module returns the following command.

For example, 55 AA 00 04 00 00 03

Send commands (0x06)

• For more information about DPs, see the description of DP format.
• This command can only be used to send the data unit of a single DP to the MCU.
• This is an asynchronous command, corresponding to status reporting. For example, the module sends a command to turn off the light and the MCU sends 0x07 to return the current on/off status after executing the control command.

The module sends the following command.

• DP format (data of a single DP)

  1	2	3 to 4	5 and followings
  dp1_id	dp1_type	dp1_len	dp1_data

• For example, the MCU sends 55 aa 00 06 00 05 03 01 00 01 01 10, representing information described in the following table.

  Data	Field	Value
  03	dp1_id	3
  01	dp1_type	Boolean
  00 01	dp1_len	1 byte
  01	dp1_data	true

The MCU returns the following command.

None

Report status (0x07)

• For more information about DPs, see the description of DP format.
• The MCU can report the status of multiple DPs at the same time.
• This is an asynchronous command. The MCU uses it to report device status to the module, which can be triggered by three mechanisms.
  • After the MCU executes the command received from the module, it reports the changed DP status to the module.
  • When the MCU proactively detects status changes of DPs, it reports the changed DP status to the module.
  • When the MCU receives the DP status query, it sends the status of all DPs to the module.

The MCU sends the following command.

• DP format (data of a single or multiple DPs)

  1	2	3 to 4	5 and followings	…	n	n+1	n+2 to n+3	n+4 and followings
  dp_id	dp_type	dp_len	dp_data	…
  dpN_id	dpN_type	dpN_len	dpN_data

• For example, 55 aa 00 07 00 05 03 01 00 01 01 11

The module returns the following command.

Query status (0x08)

• This is an asynchronous command. The module uses it to query the current status of all DPs. The MCU will report the data the module queries through the command 0x07.
• The module sends a status query when the following two events occur.
  • For a paired module, it detects that the MCU is restarted based on the heartbeat communication.
  • Users open the control panel of a device on the mobile app.

The module sends the following command.

For example, 55 aa 00 08 00 00 07

The MCU returns the following command.

None

Production test

Radio frequency (RF) (0x0E)

• Perform the received signal strength indicator (RSSI) test on modules to measure the RF performance.
• Test tool: a Bluetooth beacon that broadcasts an identifier named ty_mdev.
• Test steps: Put the beacon around 0.5 meters away from the module. The MCU sends this command to the module to initiate a test. The module will search for the designated identifier and return the RSSI. If the RSSI is greater than -70 dB, the RF performance is acceptable.
  The module must be unpaired and operate in the standard power mode. If the module is paired and powered for 15 minutes, the module can never enter the test mode again.

The MCU sends the following command.

The module returns the following command.

Data format

Low power protocol

Enable low power mode (0xE5)

• The MCU can power on or off the module with a triode to reduce power consumption. In the low power mode, unnecessary communication is reduced to speed up the initialization process and enable the module to quickly boot from the power-off state.

  

• Circuit design

  

• After the MCU wakes up the module to report DP status, the length of a DP determines how long the module is in the power-on state. You can use this formula to get the duration: (DP length + 3)/4 × 400 ms

The MCU sends the following command.

Data format

The module returns the following command.

Mesh-specific protocols

Enable communication between nodes (0xB1)

• This feature is available on mobile app v3.20 and later.

• After communication between nodes is enabled, the module will request eight publish addresses (pub_address) from the cloud and save them to the storage. At the same time, quick pairing is disabled. In quick pairing mode, a device can be added to the mobile app within 3 to 5 seconds. With this mode disabled, the time will be about 10 seconds.

• The following figure shows how to enable local device linkage with eight publish addresses.

  

  As shown above, open the control panel of the Bluetooth remote control. Tap Configure group A.

  The destination address of group A is one of the eight publish addresses.

  How to set up local linkage:

  1. The mobile app requests the publish address assigned to group A from the cloud.
  2. The mobile app requests the current device list of group A and the list of devices that can be added to this group.
  3. Users can add or remove a device. The mobile app will send a command to the physical device accordingly.

  How to implement local linkage:

  1. Press the ON button on the remote control.
  2. The remote control will set the received publish address as the destination address and send the on/off control command to the target group.
  3. The smart lights in the target group will be turned on or off accordingly.

The MCU sends the following command.

Data format

The module returns the following command.

Nodes communicate with each other (0xB2)

• The communication between nodes in a Bluetooth mesh network makes the local device linkage possible.

• The precondition is that the sender has got the address of the receiver in advance, which can be implemented through the following methods.

  • Method 1: When the sender is added to the mobile app, you can assign eight publish addresses to it and add devices to these eight groups as needed. For example, a remote control (the sender) features eight groups.
  • Method 2: Broadcast control commands. Set the destination address to 0xFFFF.
  • Method 3: The sender reads and sets the address of the group it belongs to as the destination address. This way, devices in the same group can be linked. For example, in a parking lot, a row of PIR lights can be turned off when a light receives a command.
  • Method 4: Send a DP command to the sender by using the mobile app. The destination address will be included in the command.

• Things to note

  • The Bluetooth mesh generic firmware v0.9 only supports method 2 and method 4.
  • v1.0 supports method 3.
  • v1.1 supports method 4.

The MCU sends the following command.

Data format

Get eight publish addresses (0xB3)

The MCU can request the eight publish addresses (pub_address) from the Bluetooth module.

The MCU sends the following command.

The module returns the following command.

Data format

Query the group a device belongs to (0xB4)

The typical application of this command is group control in commercial lighting. For example, if a row of lights is added to one group when one of a light detects a coming vehicle, it will send a command to turn on the rest lights.

The MCU sends the following command.

The module returns the following command.

Data format

Sync the remote with a device through hardware operations (0xB5)

You can sync the remote control with devices through hardware operations without using the mobile app, as shown in the following steps.

• Use the command 0xB6 to make a device enter sync mode through an external event trigger such as a button press or power-on.
• Use the command 0xB5 to make the remote control start syncing with the device through an external event trigger such as a button press.
• The LED indicator of the device that the remote control successfully syncs with will blink.
• This way, the remote control can send messages to the publish address through the command 0xB2.

The MCU sends the following command.

Data format

The module returns the following command.

Enable time window (0xB6)

The command 0xB5 enables a device to act as a remote control to sync with and control other devices. The command 0xB6 enables a device to be synced with and controlled by a remote control.

However, the time window for the sync process is not always on. The command 0xB6 is used to turn on the time window. The duration setup is also supported. This way, remote controls can sync with devices only in the specified time window. For example:

• Light bulbs: A time window is turned on for 10 seconds after the light bulb is powered on.
• Power strip: A time window is turned on for 10 seconds after a button is pressed and held.

The MCU sends the following command.

The module returns the following command.

Add to favorites (0xB7)

This command applies to devices that support the favorites feature. It allows users to add the setup of a device to favorites so that they can quickly restore the device to this saved setup. Up to four setups can be added.

For example, users can adjust a group of devices to the desired setting and add the current setup to the favorite so that they can apply one of the saved setups to the device with one tap.

The MCU sends the following command.

Data format

The module returns the following command.

Notification of adding favorites (0xB8)

The module sends the following command.

Data format

The MCU returns the following command.

Send messages defined by standard mesh models (0xBC)

This command is used to send messages defined by standard mesh models to a publish address. For example, a Bluetooth remote control can send messages to switch on or dim lights.

The standard models adopted in the Tuya protocol.

The MCU sends the following command.

Data format

The module returns the following command.

Receive messages defined by standard mesh models (0xBD)

This command is used to receive messages defined by standard mesh models. For example, Bluetooth lights can receive messages from a remote control.

The module sends the following command.

Data format

The MCU returns the following command.

Send messages defined by vendor-specific mesh models (0xBE)

This command is used to send messages defined by vendor-specific mesh models to a publish address. For example, a Bluetooth remote control can send messages to Bluetooth lights to switch between lighting scenes.

The MCU sends the following command.

Data format

The module returns the following command.

Receive messages defined by vendor-specific mesh models (0xBF)

This command is used to receive messages defined by vendor-specific mesh models. For example, Bluetooth lights can receive messages from a remote control.

The module sends the following command.

Data format

The MCU returns the following command.

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