Bluetooth LE SoC Board (BK3432)

The Tuya Sandwich Bluetooth SoC has BK3432 chip as a microcontroller, which is designed to help you easily prototype your IoT ideas. It can work with functional boards or circuit boards to implement specific features.

Applications

• This development board applies to a wide range of prototypes implemented with Tuya’s no-code solutions, such as sockets, power strips, and switches.

• Develop with the board to build your IoT projects easily and fast.

• You can use this board for different development purposes.

  • Embedded program development and debugging
  • App development and debugging
  • Creating connected devices that can be controlled with a mobile phone
  • Getting started with IoT development and learning how the Bluetooth-based control system works

Components

The development board uses the cost-effective Bluetooth chip BK3432 from Beken Corporation. It has on-board buttons, GPIOs, BK3432 programmer, and a USB-to-serial chip.

I/O port and pin description

1. DIP switch (S1): Flip the toggle to the ON position to complete the circuit. The switch is used to open and close the circuit between the USB-to-serial chip and the chip’s serial port.
2. Micro-USB (CN1): Inputs 5V DC voltage and provides two extended serial ports.
3. Button (S2): When the button is pressed, P10 on BK3432 outputs low. When the button is released, it outputs high.
4. Button (S2): It is connected to the RST pin on BK3432. When the button is pressed, the RST pin outputs low. When the button is released, it outputs high.
5. Button (S4): It is used for flashing firmware to the chip BK3432. Do not press this button unless you start firmware flashing.
6. Pin header (P2): It is used to change the connection of UART0 on the USB-to-serial chip. When you place a jumper cap on the NORMAL position, UART0 is connected to UART2 on the chip BK3432. When the jumper cap is placed on the DOWNLOAD position, UART0 is used to flash firmware to BK3432.
7. DIP switch (S5): Flip the toggle to the ON position to complete the circuit. The switch is used to open and close the circuit of BK3432 firmware flashing.
8. Pin header (P4): It is used to flash firmware to the chip U1 BK7231.

• Pin description

  No.	Pin name	Description
  1	NC	Leave it floating.
  2	NC	Leave it floating.
  3	NC	Leave it floating.
  4	3.3V	3.3V power pin.
  5	5V	5V power pin.
  6	GND	Ground pin.
  7	GND	Ground pin.
  8	12V	12V power pin. Leave this pin floating because the board does not have a DC power jack (DC-005).
  9	P31	GPIOP_31 on BK3432, which can be reused as the ADC channel 1.
  10	P32	GPIOP_32 on BK3432, which can be reused as the ADC channel 2.
  11	P35	GPIOP_35 on BK3432, which can be reused as the ADC channel 5.
  12	P34	GPIOP_34 on BK3432, which can be reused as the ADC channel 4.
  13	P33	GPIOP_33 on BK3432, which can be reused as the ADC channel 3.
  14	NC	Leave it floating.
  15	P17	GPIOP_17 on BK3432, which can be reused as the UART2_RX.
  16	P16	GPIOP_16 on BK3432, which can be reused as the UART2_TX.
  17	P14	GPIOP_14 on BK3432, which can be reused as the PWM4.
  18	P12	GPIOP_12 on BK3432, which can be reused as the PWM2.
  19	P13	GPIOP_13 on BK3432, which can be reused as the PWM3.
  20	P11	GPIOP_11 on BK3432, which can be reused as the PWM1.
  21	P10	GPIOP_10 on BK3432, which can be reused as the PWM0.
  22	NC	Leave it floating.
  23	P01	GPIOP_01 on BK3432, which can be reused as the UART1_RX.
  24	P00	GPIOP_00 on BK3432, which can be reused as the UART1_TX.
  25	P07	GPIOP_07 on BK3432, which can be reused as the SPI NSS.
  26	P05	GPIOP_05 on BK3432, which can be reused as the SPI MOSI.
  27	P06	GPIOP_06 on BK3432, which can be reused as the SPI MISO.
  28	P04	GPIOP_04 on BK3432, which can be reused as the SPI CLK.
  29	GND	Ground pin.
  30	NC	Leave it floating.
  31	P03	GPIOP_03 on BK3432, which can be reused as the I2C SCL.
  32	P02	GPIOP_02 on BK3432, which can be reused as the I2C SCL.

Load-carrying capacity

• When micro-USB (CN1) inputs 5V DC voltage, the board can supply power to external components.

  Power pin	Rated voltage/current
  VIN	Depends on the input current of the adapter connected to the micro-USB (CN1) terminal.
  3.3V	3.3V/0.6A

• Characteristics of the output voltage of VDD

• Characteristics of output voltage

  Output current	0A	0.15A	0.3A	0.45A	0.6A	0.75A
  Output voltage	3.34V	3.36V	3.37V	3.37V	3.38V	3.38V

  Note: We tested the voltage under the condition that there is no output voltage on the micro-USB (CN1) terminal.

Schematic diagram and PCB

• The schematic diagram of the board:

  

• The PCB board:

  

  

How USB-to-serial works

• The board has a built-in USB-to-serial chip. The single-channel USB port can provide two extended serial ports. You can flip the DIP switch (S1) to enable the 2-channel serial port on the BK3432 to connect to the USB-to-serial chip. The following table lists the pin definition of the DIP switch.

  No.	1	2	3	4
  Pins on BK3432	UART2_TX	UART2_RX	UART1_TX	UART1_RX
  UART ports on the board	USB-RXD0	USB-TXD0	USB-RXD1	USB-TXD1

  Note: Flip the toggle to the ON position to complete the circuit.

• The COM ports map to the UART ports as follows.
  

  No.	1	2
  COM ports on the computer	SERIAL-A(COM23)	SERIAL-B(COM22)
  UART ports on the board	USB-UART0	USB-UART1

Note: The COM port number varies depending on computers so we use SERIAL-A and SERIAL-B to indicate the two COM ports.

Connection for DOWNLOAD mode

1. Flip the four DIP switch (S1) toggles to the ON position to complete the UART circuit.
2. Flip the four DIP switch (S5) toggles to the ON position to complete the firmware flashing circuit.
3. Place the jumper cap on DOWNLOAD position to enable USB-UART0 to switch to flashing mode.
4. Connect WP pin and GND pin on the P4 pin header using a jumper wire to enable flashing mode.

   Note: If you do not have a jumper wire, before firmware flashing starts, press and hold the button S4 until the flashing is completed.

5. Connect the board to your computer using a USB cable to build serial communication.
6. Verify that the power LED is on.
   The picture above shows how the connection should be done. Then, your board is ready for firmware flashing.

Connection for NORMAL mode

1. Flip the four DIP switch (S1) toggles to the 1, 2, 3, and 4 to release the UART resources.
2. Flip the four DIP switch (S5) toggles to the 1, 2, 3, and 4 to release the SPI resources.
3. Place the jumper cap on NORMAL position to enable development mode.
4. Connect the board to your computer using a USB cable to build serial communication.
5. Verify that the power LED is on.
   The picture above shows how the connection should be done. Then, your board is ready for development.

Connection between the host and UART1

Complete the connection for NORMAL mode, as shown in the picture above. Then, you can proceed with the following steps.
Flip the DIP switch (S1) toggle 3 and 4 to the ON position. Connect the UART1 to the USB-to-serial chip. Therefore, P00 and P01 are used for UART communication and cannot be connected to other peripherals.

Connection between the host and UART2

Complete the connection for NORMAL mode, as shown in the picture above. Then, you can proceed with the following steps.
Flip the DIP switch (S1) toggle 1 and 2 to the ON position. Connect the UART2 to the USB-to-serial chip. Therefore, P16 and P17 are used for UART communication and cannot be connected to other peripherals.

USB-to-serial chip driver

Download the USB-to-serial chip driver for your operating system.

• For Windows
• For Linux

Things to note

• The board has a built-in power supply port and circuit, so the additional power board is not necessary.
• Because the SPI and UART peripherals are used for flashing, if the I/O is occupied, check whether the DIP switch is in the ON position.