STC51 minimum core board

This project is a minimal learning board based on STC51. (There are still some problems that are still being modified)

The first is the smallest system part of the microcontroller. It includes crystal oscillator, download circuit, reset circuit and pull-up of P0.

Then there is the USB power supply and downloading part. Using the square USB port makes welding and debugging more convenient. Adding a switch facilitates the control of power and power outages for the entire board. The input voltage is stabilized to 3V3 through LM1117. Convenient to control the power supply of some sensors. At the same time, power indicator lights are added to both 3V3 and 5V, so you can clearly see whether the power supply is normal.

The common CH340N is used as the chip for the USB to serial port circuit. Through this part of the circuit, the USB signal can be simulated into a serial port, so that the computer and the microcontroller can communicate. It is convenient for us to download programs and read and use the serial port.

Peripheral 1_Flowing water lamp: Use eight light-emitting diodes to form a running water lamp circuit. Use an exclusion resistor as a current-limiting resistor to control the brightness of the LED. Similarly, the eight LEDs can also be used as indicator lights during subsequent debugging and use of the board. It is convenient for us to check the status of the board.

Peripheral 2_Buzzer circuit: A buzzer circuit composed of a switch composed of a passive buzzer and a transistor. The PWM wave input through BEEP can be used to control the switch of the transistor and the conduction of the buzzer, thereby achieving control of different tones.

, playing beautiful music. Including later use, you can also use the buzzer to judge the running status of the board.

Peripheral three_independent buttons and matrix buttons: including two independent buttons and a 2*2 matrix button. As a signal input for human-computer interaction. Used to control the operation of some programs on the microcontroller.

Peripheral 4_Communication protocol interface: Set aside an IIC and an SPI protocol communication interface, which can be directly connected to a 0.96-inch display screen. Other IIC or SPI protocol sensor modules can also be connected. The IO port is used to simulate the programming of IIC and SPI.

Expansion interface_GND/3V3/5V five each. Each pin of the microcontroller leads to a separate pin. By drawing out the pins, it will be more convenient for us to use more modules for wiring and verification in later learning.