如何利用寄存器实现LED序列的永久循环（模拟尾灯效果）

Hey there! Let's figure out how to build that LED tail light-style permanent loop using registers. I'll walk you through the whole process, from core logic to practical code examples, so you can follow along easily.

The key here is using a register to track your LEDs' active state. We'll start with the leftmost LED lit, shift the "on" position one step to the right each cycle, and once we hit the rightmost LED, we reset the register back to its initial state to kick off the loop all over again.

• First, set up a register (can be a hardware shift register or a software variable acting as a register) to store which LED is active. For 8 LEDs, start with the value 0b00000001—this means only the leftmost LED is turned on.
• In your main loop, first output the register's value to your LED port so the corresponding LED lights up.
• Then, shift the register left by one bit to move the "on" state to the next LED in line.
• Add a critical check: when the register reaches 0b10000000 (rightmost LED active), the next shift would turn all LEDs off. Instead, we reset the register back to 0b00000001 to restart the cycle.

Here's a practical C snippet using a software register (a unsigned char variable) to mimic hardware register behavior:

#include <reg51.h>

// Assume LEDs are connected to Port P1
#define LED_PORT P1

void delay_ms(unsigned int ms) {
    unsigned int i, j;
    for(i = ms; i > 0; i--)
        for(j = 110; j > 0; j--);
}

void main() {
    // Our "register" to track LED state—starts with leftmost LED on
    unsigned char led_state_reg = 0x01;

    while(1) { // Permanent loop
        LED_PORT = led_state_reg; // Output register state to LEDs
        delay_ms(500); // Delay so we can see the transition
        
        // Check if we've reached the rightmost LED
        if(led_state_reg == 0x80) {
            led_state_reg = 0x01; // Reset to initial state
        } else {
            led_state_reg <<= 1; // Shift left to activate next LED
        }
    }
}

• If you're using a hardware shift register (like the 74HC595), the logic stays identical—you'd send serial data to shift the register state instead of using a software variable, but the cycle reset rule is the same.
• For more than 8 LEDs, just adjust the register size and reset threshold. For 16 LEDs, use a unsigned int register and check for 0x8000 before resetting.
• This approach is super efficient because register operations are fast, and the loop runs continuously with minimal overhead.

内容的提问来源于stack exchange，提问作者Frixion