Wi-Fi & Bluetooth LE SoC NANO (BK7231N)

The Tuya Sandwich Wi-Fi and Bluetooth LE combo SoC NANO has BK7231N 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, switches, and lights.
• 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 Wi-Fi-based control system works

Components

The development board is integrated with the cost-effective Wi-Fi and Bluetooth LE combo chip BK7231N from Beken Corporation. It has on-board buttons, LED, GPIOs, and a USB-to-serial chip.

I/O port and pin description

1. Micro-USB (CN1): Inputs 5V DC voltage and provides two extended serial ports
2. 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.
3. LED indicator (D3): When the 3.3V power is on, the LED is on.
4. Button (S2): When the button is pressed, P9 outputs low. When the button is released, it outputs high.
5. LED indicator (D2): When P16 outputs low, the LED is on.
6. Button (RST): When the button is pressed, P9 outputs low. When the button is released, it outputs high.

• Pin description

  No.	Pin name	Description
  1	NC	Leave it floating.
  2	3.3V	3.3V power pin.
  3	NC	Leave it floating.
  4	NC	Leave it floating.
  5	NC	Leave it floating.
  6	P26	GPIOP_26 on BK7231N, which can be reused as the PWM5.
  7	P24	GPIOP_24 on BK7231N, which can be reused as the PWM4.
  8	P23	GPIOP_23 on BK7231N, which can be reused as the ADC.
  9	P28	GPIOP_28 on BK7231N.
  10	P22	GPIOP_22 on BK7231N.
  11	P21	GPIOP_21 on BK7231N, which can be reused as the I2C1 SDA.
  12	5V	5V power pin.
  13	RST	Clock enable (CEN) pin on BK7231N. It can output the chip enable and high enable signals.
  14	GND	Ground pin.
  15	NC	Leave it floating.
  16	P11	GPIOP_11 on BK7231N, which can be reused as the UART1 TXD pin and generally used as the user I/O.
  17	P10	GPIOP_10 on BK7231N, which can be reused as the UART1 RXD pin and generally used as the user I/O.
  18	RST	Clock enable (CEN) pin on BK7231N. It can output the chip enable and high enable signals.
  19	GND	Ground pin.
  20	P09	GPIOP_09 on BK7231N, which can be reused as the PWM3.
  21	P20	GPIOP_20 on BK7231N, which can be reused as the I2C1 SCL.
  22	P01	GPIOP_01 on BK7231N, which can be reused as the UART2 RXD pin, generally used for log printing.
  23	P00	GPIOP_00 on BK7231N, which can be reused as the UART2 TXD pin, generally used for log printing.
  24	P08	GPIOP_08 on BK7231N, which can be reused as the PWM2.
  25	P07	GPIOP_07 on BK7231N, which can be reused as the PWM1.
  26	P06	GPIOP_06 on BK7231N, which can be reused as the PWM0.
  27	P14	GPIOP_14 on BK7231N, which can be reused as the SPI SCK.
  28	P16	GPIOP_16 on BK7231N, which can be reused as the SPI MOSI.
  29	P15	GPIOP_15 on BK7231N, which can be reused as the SPI CSN.
  30	P17	GPIOP_17 on BK7231N, which can be reused as the SPI MISO.

Load-carrying capacity

• When micro-USB (CN1) 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.
  3.3V	3.3V/0.6A

• 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 BK7231N to connect to the USB-to-serial chip. The following table lists the pin definition of the DIP switch.

  DIP switch No.	1	2	3	4
  BK7231N chip	UART1_RX	UART1_TX	UART2_RX	UART2_TX
  USB-to-serial chip	USB-TX0	USB-RX0	USB-TX1	USB-RX1

Note:

• 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.
• When you use the UART pin on the chip for communication with an MCU or GPIO, flip the toggle of the corresponding channel to the OFF position (the side with numbers) to open the circuit between the UART on BK7231N and the USB-to-serial chip.

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

  COM ports on the computer	SERIAL-A(COM23)	SERIAL-B(COM22)
  USB-to-serial chip	USB-UART0	USB-UART1
  BK7231N chip	UART1	UART2

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

Flip the toggles of channel 1 and 2 on the DIP switch (S2) to the ON position to complete the circuit between the UART1 on BK7231N and the host.

Connection for viewing logs on the host

Flip the toggles of channel 3 and 4 on the DIP switch (S2) to the ON position to complete the circuit between the UART2 on BK7231N and the host.

Connection for user I/O and host communication

Flip the toggles of channel 1 and 2 on the DIP switch (S2) to the ON position to complete the circuit between the UART1 on BK7231N and the host.

Connection for using both UARTs as GPIOs

Flip the toggles of channel 1 to 4 on the DIP switch (S2) to the OFF position to open the circuit between the UARTs on BK7231N and the USB-to-serial chip.

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.
• This board only supports USB port that supplies 5V output.
• If you want to use P10, P11, P00, and P01 for other circuits, make sure to flip the toggle of the corresponding channel to the OFF position to open the circuit between the UART on BK7231N and the USB-to-serial chip.