Product features
High-speed ARM9E core MCU
2.4G/1T1R
160k programming space, 20KB RAM
Power supply voltage 0.9-3.6v
Ultra low supply voltage, low power consumption
Built-in crystal, high stability
Small chip package 4x4
Rich peripheral interface, SPI, I2C, ADC, UART, PWM, GPIO
Widely used in the Internet of Things
High-speed 10-bit multi-channel ADC with internal filtering
Easy to connect, fast speed

Function description
The module function is mainly to realize the mutual conversion of serial data.
In this mode, the HLK-B20 module sends the received data from the serial port.
Serial port working state conversion

Figure: Serial port working state transition
The module defines the working state of the serial port as two modes: transparent transmission mode and AT command mode.
After normal power-on, the module directly enters the transparent mode. In any state, keeping the ES0 pin low for longer than Tes and less than Trst will immediately enter the AT command mode