c51中代码要求可以用1602液晶屏的显示驱动，矩阵键盘输入液晶屏显示输出 ，串口下位机发送数据 ，串口下位机接收数据代码

以下是一个简单的示例代码，用于在C51中使用1602液晶屏进行显示，同时通过矩阵键盘进行输入，并通过串口与下位机进行数据通信：

#include <reg52.h>
#include <stdio.h>

#define LCD_DATABUS P0
sbit LCD_RS = P2^0;
sbit LCD_RW = P2^1;
sbit LCD_EN = P2^2;
sbit KEYPAD_ROW1 = P1^0;
sbit KEYPAD_ROW2 = P1^1;
sbit KEYPAD_ROW3 = P1^2;
sbit KEYPAD_ROW4 = P1^3;
sbit KEYPAD_COL1 = P1^4;
sbit KEYPAD_COL2 = P1^5;
sbit KEYPAD_COL3 = P1^6;
sbit KEYPAD_COL4 = P1^7;
sbit UART_TX = P3^1;
sbit UART_RX = P3^0;

void InitLCD(void);
void SendCommand(unsigned char cmd);
void SendData(unsigned char dat);
void DisplayString(unsigned char x, unsigned char y, unsigned char *str);
void DelayUs2x(unsigned char t);
void DelayMs(unsigned char t);
unsigned char KeypadScan(void);
void InitUART(void);
void SendByte(unsigned char dat);
unsigned char ReceiveByte(void);

void main(void)
{
    unsigned char keypad_val = 0;
    unsigned char uart_rx_data = 0;
    unsigned char str[16] = {0};
    
    InitLCD();
    InitUART();
    
    DisplayString(0, 0, "Keypad:");
    DisplayString(0, 1, "UART:");
    
    while (1)
    {
        keypad_val = KeypadScan();
        if (keypad_val != 0)
        {
            sprintf(str, "%d", keypad_val);
            DisplayString(8, 0, str);
        }
        
        if (RI)
        {
            uart_rx_data = ReceiveByte();
            sprintf(str, "%d", uart_rx_data);
            DisplayString(5, 1, str);
        }
    }
}

void InitLCD(void)
{
    SendCommand(0x38); // function set: 8-bit, 2-line, 5x8 dots
    SendCommand(0x0c); // display on, cursor off, blink off
    SendCommand(0x06); // entry mode set: increment, no shift
    SendCommand(0x01); // clear display
    DelayMs(2); // wait for clear display command to finish
}

void SendCommand(unsigned char cmd)
{
    LCD_RS = 0;
    LCD_RW = 0;
    LCD_EN = 1;
    LCD_DATABUS = cmd;
    DelayUs2x(10);
    LCD_EN = 0;
}

void SendData(unsigned char dat)
{
    LCD_RS = 1;
    LCD_RW = 0;
    LCD_EN = 1;
    LCD_DATABUS = dat;
    DelayUs2x(10);
    LCD_EN = 0;
}

void DisplayString(unsigned char x, unsigned char y, unsigned char *str)
{
    unsigned char addr = 0;
    if (y == 0)
    {
        addr = 0x80 + x;
    }
    else if (y == 1)
    {
        addr = 0xc0 + x;
    }
    SendCommand(addr);
    while (*str != '\0')
    {
        SendData(*str++);
    }
}

void DelayUs2x(unsigned char t)
{
    while (t--)
    {
        _nop_();
        _nop_();
    }
}

void DelayMs(unsigned char t)
{
    while (t--)
    {
        DelayUs2x(245);
        DelayUs2x(245);
    }
}

unsigned char KeypadScan(void)
{
    unsigned char row = 0;
    unsigned char col = 0;
    unsigned char keypad_val = 0;
    
    KEYPAD_ROW1 = 0;
    KEYPAD_ROW2 = 1;
    KEYPAD_ROW3 = 1;
    KEYPAD_ROW4 = 1;
    DelayUs2x(5);
    col = KEYPAD_COL1 & KEYPAD_COL2 & KEYPAD_COL3 & KEYPAD_COL4;
    if (!col)
    {
        row = 1;
    }
    
    KEYPAD_ROW1 = 1;
    KEYPAD_ROW2 = 0;
    KEYPAD_ROW3 = 1;
    KEYPAD_ROW4 = 1;
    DelayUs2x(5);
    col = KEYPAD_COL1 & KEYPAD_COL2 & KEYPAD_COL3 & KEYPAD_COL4;
    if (!col)
    {
        row = 2;
    }
    
    KEYPAD_ROW1 = 1;
    KEYPAD_ROW2 = 1;
    KEYPAD_ROW3 = 0;
    KEYPAD_ROW4 = 1;
    DelayUs2x(5);
    col = KEYPAD_COL1 & KEYPAD_COL2 & KEYPAD_COL3 & KEYPAD_COL4;
    if (!col)
    {
        row = 3;
    }
    
    KEYPAD_ROW1 = 1;
    KEYPAD_ROW2 = 1;
    KEYPAD_ROW3 = 1;
    KEYPAD_ROW4 = 0;
    DelayUs2x(5);
    col = KEYPAD_COL1 & KEYPAD_COL2 & KEYPAD_COL3 & KEYPAD_COL4;
    if (!col)
    {
        row = 4;
    }
    
    if (col == 0x08)
    {
        keypad_val = row * 3;
    }
    else if (col == 0x04)
    {
        keypad_val = row * 3 + 1;
    }
    else if (col == 0x02)
    {
        keypad_val = row * 3 + 2;
    }
    else
    {
        keypad_val = 0;
    }
    
    return keypad_val;
}

void InitUART(void)
{
    TMOD = 0x20; // timer1 mode 2: 8-bit auto-reload
    TH1 = 0xfd; // 9600 baud rate
    TL1 = 0xfd;
    TR1 = 1; // start timer1
    TI = 1; // enable transmit interrupt
    ES = 1; // enable serial interrupt
}

void SendByte(unsigned char dat)
{
    SBUF = dat;
    while (!TI);
    TI = 0;
}

unsigned char ReceiveByte(void)
{
    unsigned char uart_rx_data = 0;
    while (!RI);
    uart_rx_data = SBUF;
    RI = 0;
    return uart_rx_data;
}

void UARTInterrupt(void) interrupt 4
{
    if (RI)
    {
        RI = 0;
    }
    if (TI)
    {
        TI = 0;
    }
}

在这个代码中，使用了1602液晶屏进行显示，使用矩阵键盘进行输入。同时，使用了串口与下位机进行通信。具体来说：

- `InitLCD`函数用于初始化液晶屏。
- `SendCommand`函数用于发送命令到液晶屏。
- `SendData`函数用于发送数据到液晶屏。
- `DisplayString`函数用于在液晶屏上显示字符串。
- `DelayUs2x`和`DelayMs`函数用于延时，以等待液晶屏响应。
- `KeypadScan`函数用于扫描矩阵键盘，并返回按键值。
- `InitUART`函数用于初始化串口。
- `SendByte`函数用于向下位机发送一个字节的数据。
- `ReceiveByte`函数用于从下位机接收一个字节的数据。
- `UARTInterrupt`是串口中断服务函数，在接收到数据时触发。

在主函数中，首先调用`InitLCD`和`InitUART`函数进行初始化。然后在循环中不断扫描矩阵键盘和串口，如果有按键按下或者接收到数据，就在液晶屏上显示相应的内容。