Serial dynamic LED scanning circuit and program list

4 uses C2051 microcontroller, and uses cheap and easy-to-get 74LS164 and 74LS138 as expansion chips. 74LS164 is an 8-bit serial input and parallel output shift register. Its function here is to decode the serial data output by the C2051 serial communication port and output it on its parallel port line, thereby driving the LED digital tube. 74LS138 is a 3-8 decoder, which decodes the address signal output by the microcontroller and dynamically drives the corresponding LED. However, the current driving capacity of 74LS138 is relatively small. For this reason, the circuit uses the final driving transistor 2SA1015 as the address driver.
The segments of the four LEDs are connected together, and their common ends are time-sharingly selected by 74LS138. In this way, at any time, only one LED is lit, which is a dynamic scanning display mode. Using the serial port for LED communication, the program writing is quite simple. The user only needs to send the data to be displayed directly to the serial port send buffer and wait for the serial interrupt. Take a look at the following program. ·

Program List