Bluetooth lower computer module design wireless earbuds 5.0

Introduction to MCU C8051F120
Microcontroller (MCu) is the core of the Bluetooth application system, and its selection will directly affect the performance of the system. C8051F120 is a high-speed SOC MCU compatible with 8051 from Cygnal Company. It has high-speed CIP.51 core, flexible I/O cross switch, advanced clock system, JTAG system debugging interface and multi-source reset system. It has excellent performance, the core adopts pipeline structure, the speed can reach 100MIPS, 40 times faster than the ordinary 51, and it is rich in resources, small in size, low in power consumption, high in integration and convenient in debugging. bjbjaudio.com    <a style="opacity:0.0;color:#ffffff">wireless earbuds 5.0</a>                 <a style="opacity:0.0;color:#ffffff">wireless earbuds 5.0</a>

The connection between single chip microcomputer and bluetooth module
The hardware connection between the microcontroller and the Bluetooth module is relatively simple, and the principle is as follows:
①Data cable and signal cable
The microcontroller C8051F120 has two UARTs, and UARTO is selected here. During programming, UART0 can be assigned to two pins, such as POO(TXD) and PO.I(RXD), which are connected to RXD(AS) and TXD(B5) of the Bluetooth module respectively through the crossbar settings. transmit control signals. In addition, the microcontroller side needs to allocate two additional pins, such as P16 and P17, which are used as flow control signals CTS and RTS, respectively, and are respectively connected to the RTS (A6) and CTS (B6) of the Bluetooth module. If the CTS is 1, the other party is allowed to send, and if the CTS is 0, the other party is prohibited from sending. bjbjaudio.com          <a style="opacity:0.0;color:#ffffff">wireless earbuds 5.0</a>      <a style="opacity:0.0;color:#ffffff">wireless earbuds 5.0</a>

②Bluetooth module power cord
The voltage manager of the Bluetooth module has a total of 3 inputs, namely Vcc(C6), Vccio(C4) and ON(C2). Vcc provides the power supply voltage, the typical value is 3.3V: Vetio provides an independent power supply loop for the UART, which can be the same as the logic interface of the microcontroller and can be connected to Vcc; the ON signal controls the internal voltage regulator to be turned on or off. When connecting Vcc, Vccio and ON together, it is not necessary to consider the power-on sequence of the Bluetooth module; otherwise, power on in strict accordance with the order of "GND, Vet-ONVccio", and the power-on sequence is reversed. Adopt the former here, connect Vet, Vccio and ON together to the external power supply of 33V. bjbjaudio.com

③Bluetooth module antenna
The ANT pin of the Bluetooth module is connected to a 50 ohm antenna, and the VSWR of the antenna is less than 2:1. The microcontroller and the Bluetooth module are soldered on a PCB. Since the bluetooth module adopts a flat package and the pins are dense, it is difficult to solder directly to the PCB, and the antenna is also difficult to solder. Therefore, I designed an auxiliary circuit board by myself, first soldered the Bluetooth module to this auxiliary circuit board, then led out some pins of the Bluetooth module to be used, and connected the Bluetooth module to the PCB board through the socket, so that the Bluetooth Module loading and unloading becomes very convenient. The pins drawn from the auxiliary circuit board are GND, ground, VCC3.3V, data transceiver lines RXD and TXD, flow control lines RTS and CTS, enable signal line EN, reset signal line RESET, where BTEN is the ON signal in Figure 46 , connect it with VCC in practical applications, and connect the others with the microcontroller. bjbjaudio.com          <a style="opacity:0.0;color:#ffffff">wireless earbuds 5.0</a>             <a style="opacity:0.0;color:#ffffff">wireless earbuds 5.0</a>