Wi-Fi and Bluetooth Low Energy Combo Core Board (BK7252)

Tuya Sandwich Wi-Fi and Bluetooth Low Energy (LE) combo core board is designed for audio and video applications. It contains a rich set of peripherals, such as I2C, SPI, PWM, ADC, and SD card interface. You can connect to a range of external peripheral devices or Tuya Sandwich series boards.

Scenarios

The hardware on this TYDE5-BK7252-Core-1 (BK7252) core board can automatically output the captured images in JPEG. The built-in high-performance audio ADC and audio DAC are used for audio capture and playback.

• This board applies to a wide range of use cases such as smart access control systems, lockers, welcome greeting doorbells, text-to-speech readers, pet feeders, door locks, and camera doorbells.

• It can work with a GC0328 camera module to help you build image recognition solutions. Backed by the Tuya Developer Platform, you can perform custom development such as QR code scanner.

• 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 diving into the Wi-Fi-based control system, image recognition, and audio and video transmission

Components

Tuya Sandwich Wi-Fi and Bluetooth LE combo core board is based on the BEKEN’ BK7252 Wi-Fi and Bluetooth LE combo chip. It consists of CS8302M audio amplifier, two USB-C ports, CH340C USB-to-TTL chip, flip FPC connector, buttons, indicators, and other components.

I/O port functions

• 1: TTL & PWR: Provides 5V DC voltage and one extended serial port.

• 2: USB 2.0: Full-speed USB 2.0 port.

• 3: Button (CEN): When the button is pressed, the chip is reset.

• 4: Button (KEY): When the button is pressed, P5 outputs low. When the button is released, it outputs high.

• 5: Jumper (TTL to UART1/UART2): Connect TTL & PWR to UART1 or UART2 using a jumper cap.

• 6: Jumper (I2C): Connect the I2C1 on BK7252 to the I2C on the FPC connector, or disconnect them.

• 7: LED indicator: When P4 outputs low, the LED is on.

• 8: JTAG port: Compatible with the HW SPI port on the flashing tool from the chip manufacturer, used to download the program to the chip.

• 9: FPC connector: Compatible with the GC0328 and GC2145 CMOS camera modules.

• 10: MIC: 1.25 mm 2-pin microphone connector.

• 11: SPK: 1.25 mm 2-pin speaker connector, which can be connected to 8Ω 2W or 4Ω 3W speakers.

• Pin description

  No.	Symbol	Description
  1	NC	Leave it floating.
  2	+5V	5V power pin.
  3	CEN	Clock enable (CEN) pin on BK7252. It can output the chip enable and high enable signals.
  4	3.3V	3.3V power pin.
  5	+5V	5V power pin.
  6	GND	Ground pin.
  7	GND	Ground pin.
  8	NC	Leave it floating.
  9	P2	GPIOP_2 on BK7252, which can be reused as the ADC.
  10	P3	GPIOP_3 on BK7252, which can be reused as the ADC.
  11	P4	GPIOP_4 on BK7252, which can be reused as the LED pin.
  12	P5	GPIOP_5 on BK7252, which can be reused as the button pin.
  13	P0	GPIOP_0 on BK7252, which can be reused as the UART2 TXD pin, generally used for log printing.
  14	P1	GPIOP_1 on BK7252, which can be reused as the UART2 RXD pin, generally used for log printing.
  15	P10	GPIOP_10 on BK7252, which can be reused as the UART1 RXD pin and generally used as the user I/O.
  16	P11	GPIOP_11 on BK7252, which can be reused as the UART1 TXD pin and generally used as the user I/O.
  17	P13	GPIOP_13 on BK7252, which can be reused as the ADC.
  18	P12	GPIOP_12 on BK7252, which can be reused as the ADC.
  19	P19	GPIOP_19 on BK7252, which can be reused as the SD_D1.
  20	P24	GPIOP_24 on BK7252.
  21	P26	GPIOP_26 on BK7252.
  22	P17	GPIOP_17 on BK7252, which can be reused as the SD_D0.
  23	P14	GPIOP_14 on BK7252, which can be reused as the SD_CLK.
  24	P6	GPIOP_6 on BK7252, which can be reused as the PWM0.
  25	P16	GPIOP_16 on BK7252, which can be reused as the SD_CMD.
  26	P7	GPIOP_7 on BK7252, which can be reused as the PWM1.
  27	P15	GPIOP_15 on BK7252, which can be reused as the SD_D3.
  28	P18	GPIOP_18 on BK7252, which can be reused as the SD_D2.
  29	P23	GPIOP_23 on BK7252, which can be reused as the ADC and JTAG_TDO.
  30	P22	GPIOP_22 on BK7252, which can be reused as the JTAG_TDI.
  31	P21	GPIOP_21 on BK7252, which can be reused as the SDA and JTAG_TMS of the I2C1.
  32	P20	GPIOP_20 on BK7252, which can be reused as the SCL and JTAG_TCK of the I2C1.

Load-carrying capacity

• When TTL & PWR inputs 5V DC voltage, the board can supply power to external components.

  Power pin	Rated voltage/current
  5V	Depends on the input current of the adapter connected to the DC-005 terminal. The maximum output current flowing through the resettable fuse is 1A.
  3.3V	3.3V/1.0A

• Characteristics of output voltage

  Output current	0A	0.15A	0.3A	0.45A	0.6A	0.75A
  Output voltage	3.29V	3.28V	3.06V	2.95V	2.82V	2.69V

Schematic diagram and PCB

• The schematic diagram of the board:

  

• The PCB board:

  

How USB-to-TTL works

• The board has a built-in USB-to-TTL chip. The single-channel USB port can provide one extended serial port. You can use a jumper cap to allow the 2-channel serial port on the chip to connect to the USB-to-TTL chip. Pin connection description

  	CH340C	BK7252_UART1	BK7252_UART2
  Silkscreen markings	RX	TX1	TX2
  	TX	RX1	RX2

  

• The serial port on BK7252 is left floating and not connected to the pins on the USB-to-TTL chip or the core board. The six headers are open without jumper caps.

• To connect the UART 1 on the BK7252 to the USB-to-TTL chip, connect RX to TX1 and TX to RX1 by using jumper caps.

• To connect the UART 2 on the BK7252 to the USB-to-TTL chip, connect RX to TX2 and TX to RX2 by using jumper caps.

• The USB-to-TTL chip cannot connect to UART 1 and UART 2 at the same time.

Connection for flashing

For flashing license and firmware, connect pins following the table and figure shown below.

USB-to-TTL chip driver

Download the USB-to-TTL 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.

• This board contains a reserved TF card interface. You can solder the TF card components on the other side of the board if needed. The reused GPIO only works to drive the TF card.

• This board is compatible with the GC0328 and GC2145 CMOS camera modules. If you choose the GC2145 camera, you need to solder the LDO SMB130F18-C5TR (U5), peripherals, and R2 in order to start the GC2145 camera.