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虽然现在stm32用的很多，很多国产的mcu不是很贵，但是他们和8051比较，还是有一点价格的差异。这一点，如果量不大的情况下，可能不是很在乎。但是产品量比较大的话，其实就非常可观了。所以，对于gpio/uart/pwm/ad/da/时钟中断这类简单应用，很多时候，我们都会选择8051单片机进行开发，价格甚至可以降到几毛钱。不管是工具选择，还是使用过程，都非常方便。当然，如果是8266 wifi+单片机，也是常规的做法。
1、8051编译器
8051的编译器也是keil，一般是推荐先安装51版本的keil，再安装arm版本的keil。两者工程不一样，前者是uvproj，后者是uvprojx。实在安装顺序反了，也没有关系，我们可以通过自己编写bat来编译。
https://www.keil.com/download/product/2、自己准备编译bat文件
如果实在ide弄不出来，其实也没关系，写一个bat也是可以自己编译的，比如这里的run.bat，
@echo off
SET PATH=%PATH%;E:\Keil_v5\C51\BIN
SET C51INC=E:\Keil_v5\C51\INC
SET C51LIB=E:\Keil_v5\C51\LIB
del *.OBJ *.hex *.lst *.m51 2>nul
C51 main.c
A51 STARTUP.A51
BL51 main.OBJ, STARTUP.OBJ TO main
OH51 main
pause编译过程需要STARTUP.A51，还有一个main.c。其中main.c自己写，而STARTUP.A51可以在安装的keil c51目录找一下即可。找不到的话，这里拷贝改一下名字也行，
$NOMOD51
;------------------------------------------------------------------------------
; This file is part of the C51 Compiler package
; Copyright (c) 1988-2005 Keil Elektronik GmbH and Keil Software, Inc.
; Version 8.01
;
; *** <<< Use Configuration Wizard in Context Menu >>> ***
;------------------------------------------------------------------------------
; STARTUP.A51: This code is executed after processor reset.
;
; To translate this file use A51 with the following invocation:
;
; A51 STARTUP.A51
;
; To link the modified STARTUP.OBJ file to your application use the following
; Lx51 invocation:
;
; Lx51 your object file list, STARTUP.OBJ controls
;
;------------------------------------------------------------------------------
;
; User-defined <h> Power-On Initialization of Memory
;
; With the following EQU statements the initialization of memory
; at processor reset can be defined:
;
; <o> IDATALEN: IDATA memory size <0x0-0x100>
; <i> Note: The absolute start-address of IDATA memory is always 0
; <i> The IDATA space overlaps physically the DATA and BIT areas.
IDATALEN EQU 80H
;
; <o> XDATASTART: XDATA memory start address <0x0-0xFFFF>
; <i> The absolute start address of XDATA memory
XDATASTART EQU 0
;
; <o> XDATALEN: XDATA memory size <0x0-0xFFFF>
; <i> The length of XDATA memory in bytes.
XDATALEN EQU 0
;
; <o> PDATASTART: PDATA memory start address <0x0-0xFFFF>
; <i> The absolute start address of PDATA memory
PDATASTART EQU 0H
;
; <o> PDATALEN: PDATA memory size <0x0-0xFF>
; <i> The length of PDATA memory in bytes.
PDATALEN EQU 0H
;
;</h>
;------------------------------------------------------------------------------
;
;<h> Reentrant Stack Initialization
;
; The following EQU statements define the stack pointer for reentrant
; functions and initialized it:
;
; <h> Stack Space for reentrant functions in the SMALL model.
; <q> IBPSTACK: Enable SMALL model reentrant stack
; <i> Stack space for reentrant functions in the SMALL model.
IBPSTACK EQU 0 ; set to 1 if small reentrant is used.
; <o> IBPSTACKTOP: End address of SMALL model stack <0x0-0xFF>
; <i> Set the top of the stack to the highest location.
IBPSTACKTOP EQU 0xFF +1 ; default 0FFH+1
; </h>
;
; <h> Stack Space for reentrant functions in the LARGE model.
; <q> XBPSTACK: Enable LARGE model reentrant stack
; <i> Stack space for reentrant functions in the LARGE model.
XBPSTACK EQU 0 ; set to 1 if large reentrant is used.
; <o> XBPSTACKTOP: End address of LARGE model stack <0x0-0xFFFF>
; <i> Set the top of the stack to the highest location.
XBPSTACKTOP EQU 0xFFFF +1 ; default 0FFFFH+1
; </h>
;
; <h> Stack Space for reentrant functions in the COMPACT model.
; <q> PBPSTACK: Enable COMPACT model reentrant stack
; <i> Stack space for reentrant functions in the COMPACT model.
PBPSTACK EQU 0 ; set to 1 if compact reentrant is used.
;
; <o> PBPSTACKTOP: End address of COMPACT model stack <0x0-0xFFFF>
; <i> Set the top of the stack to the highest location.
PBPSTACKTOP EQU 0xFF +1 ; default 0FFH+1
; </h>
;</h>
;------------------------------------------------------------------------------
;
; Memory Page for Using the Compact Model with 64 KByte xdata RAM
; <e>Compact Model Page Definition
;
; <i>Define the XDATA page used for PDATA variables.
; <i>PPAGE must conform with the PPAGE set in the linker invocation.
;
; Enable pdata memory page initalization
PPAGEENABLE EQU 0 ; set to 1 if pdata object are used.
;
; <o> PPAGE number <0x0-0xFF>
; <i> uppermost 256-byte address of the page used for PDATA variables.
PPAGE EQU 0
;
; <o> SFR address which supplies uppermost address byte <0x0-0xFF>
; <i> most 8051 variants use P2 as uppermost address byte
PPAGE_SFR DATA 0A0H
;
; </e>
;------------------------------------------------------------------------------
; Standard SFR Symbols
ACC DATA 0E0H
B DATA 0F0H
SP DATA 81H
DPL DATA 82H
DPH DATA 83H
NAME ?C_STARTUP
?C_C51STARTUP SEGMENT CODE
?STACK SEGMENT IDATA
RSEG ?STACK
DS 1
EXTRN CODE (?C_START)
PUBLIC ?C_STARTUP
CSEG AT 0
?C_STARTUP: LJMP STARTUP1
RSEG ?C_C51STARTUP
STARTUP1:
IF IDATALEN <> 0
MOV R0,#IDATALEN - 1
CLR A
IDATALOOP: MOV @R0,A
DJNZ R0,IDATALOOP
ENDIF
IF XDATALEN <> 0
MOV DPTR,#XDATASTART
MOV R7,#LOW (XDATALEN)
IF (LOW (XDATALEN)) <> 0
MOV R6,#(HIGH (XDATALEN)) +1
ELSE
MOV R6,#HIGH (XDATALEN)
ENDIF
CLR A
XDATALOOP: MOVX @DPTR,A
INC DPTR
DJNZ R7,XDATALOOP
DJNZ R6,XDATALOOP
ENDIF
IF PPAGEENABLE <> 0
MOV PPAGE_SFR,#PPAGE
ENDIF
IF PDATALEN <> 0
MOV R0,#LOW (PDATASTART)
MOV R7,#LOW (PDATALEN)
CLR A
PDATALOOP: MOVX @R0,A
INC R0
DJNZ R7,PDATALOOP
ENDIF
IF IBPSTACK <> 0
EXTRN DATA (?C_IBP)
MOV ?C_IBP,#LOW IBPSTACKTOP
ENDIF
IF XBPSTACK <> 0
EXTRN DATA (?C_XBP)
MOV ?C_XBP,#HIGH XBPSTACKTOP
MOV ?C_XBP+1,#LOW XBPSTACKTOP
ENDIF
IF PBPSTACK <> 0
EXTRN DATA (?C_PBP)
MOV ?C_PBP,#LOW PBPSTACKTOP
ENDIF
MOV SP,#?STACK-1
; This code is required if you use L51_BANK.A51 with Banking Mode 4
;<h> Code Banking
; <q> Select Bank 0 for L51_BANK.A51 Mode 4
#if 0
; <i> Initialize bank mechanism to code bank 0 when using L51_BANK.A51 with Banking Mode 4.
EXTRN CODE (?B_SWITCH0)
CALL ?B_SWITCH0 ; init bank mechanism to code bank 0
#endif
;</h>
LJMP ?C_START
END3、准备一个main.c
最简单的main.c就是闪灯，
// main.c - STC89C52RC LED
#include <reg52.h>
sbit LED = P2^0; // LED 接在 P2.0 口（低电平点亮）
void delay_ms(unsigned int ms)
{
unsigned int i, j;
for (i = 0; i < ms; i++)
for (j = 0; j < 123; j++); // 12MHz 下约 1ms
}
void main(void)
{
while (1)
{
LED = 0;
delay_ms(100);
LED = 1;
delay_ms(100);
}
}有了这个main.c，加上之前的STARTUP.A51，这样点击一下bat，就可以编译了。最终的话，可以看到一个hex文件。
4、写一个删除bat脚本
如果出现编译错误，也会生成hex文件。这个时候可以加个pause，看下log。需要删除中间文件，就可以写一个delete.bat，
del MAIN
del main.hex
del main.LST
del MAIN.M51
del main.OBJ
del STARTUP.LST
del STARTUP.OBJ5、下载hex文件
8051基本都是用串口下载，下载的软件是stc-isp。下载的板子都是8051+一个usb转串口。所以我们只需要usb连到pc上面，然后用stc-isp下载即可，本质上就是串口编程。
下载有这么几个步骤，**1）首先需要选中芯片类型，即STC89C52RC/LE52RC，这一步非常重要；**2）其次选中串口；3）选择需要下载的hex文件；4）点击下载/编程；**5）拨动两次单片机上面的开关，一定是拨动开关，不是reset，只有这样才能下载，不然下载不了。**不出意外的话，经过这些步骤，就可以在stc-isp上面看到进度条了。
此时找一个面包板，搭建一下环境，就可以看到led闪烁了。
注1：
当然现在mm32、py32的mcu也很便宜。**对于已经使用51单片机的项目，可以继续使用51单片机。**新项目的话，可以考虑m0 mcu。
注2:
还有一种情况，就是串口通信，这也用得很多。单片的串口一般就是3.0和3.1，其中3.0是接收，3.1是发送。这里用了printf，编译生成的字节会一下子多出来不少，超过1k，之前可能只有几百个字节。这里的串口其实就是烧录的串口。
#include <reg52.h>
#include <stdio.h> // Required for printf
unsigned int cnt = 0;
void delay_ms(unsigned int ms)
{
unsigned int i, j;
for (i = 0; i < ms; i++)
for (j = 0; j < 125; j++); // Approximately 1ms at 12MHz
}
void UART_Init(void)
{
TMOD = 0x20; // Timer1, mode 2 (8-bit auto-reload)
TH1 = 0xFD; // Baud rate 9600 (11.0592MHz crystal)
TL1 = 0xFD;
TR1 = 1; // Start timer1
SCON = 0x50; // Serial mode 1 (8-bit UART), enable reception
TI = 1; // Set transmit flag to allow printf output
}
void main(void)
{
UART_Init();
while (1)
{
printf("%d\n", cnt++); // Output counter value with newline
delay_ms(10); // Delay 10ms between outputs
}
}注3：
8051的中断和arm mcu比较起来，还是比较简单的，写起来也很容易。这里还有一个好玩的现象，那就是8051的unsigned int是16位，这一点要注意下。
#include <reg52.h>
#include <stdio.h> // Required for printf
sbit LED = P2^0;
unsigned int cnt = 0;
unsigned int timer_cnt = 0;
void Timer0_ISR(void) interrupt 1
{
TH0 = 0xFC; // High 8-bit: 1ms @ 12MHz
TL0 = 0x18; // Low 8-bit: 1ms @ 12MHz
timer_cnt++;
if (timer_cnt >= 1000) // 1000ms (1000 * 1ms)
{
timer_cnt = 0;
LED = ~LED; // Toggle LED
}
}
void delay_ms(unsigned int ms)
{
unsigned int i, j;
for (i = 0; i < ms; i++)
for (j = 0; j < 125; j++); // Approximately 1ms at 12MHz
}
void Timer_Init(void)
{
TMOD &= 0xF0; // Clear T0 control bits (preserve T1 settings)
TMOD |= 0x01; // Set T0 to mode 1 (16-bit timer)
TH0 = 0xFC; // Timer for 1ms (12MHz crystal)
TL0 = 0x18; // Calculation: 65536 - 1000 = 64536 = 0xFC18
ET0 = 1; // Enable timer0 interrupt
EA = 1; // Enable global interrupt
TR0 = 1; // Start timer0
}
void UART_Init(void)
{
TMOD &= 0x0F; // ✅ Clear T1 control bits (preserve T0 settings)
TMOD |= 0x20; // Set T1 to mode 2 (8-bit auto-reload)
TH1 = 0xFD; // Baud rate 9600 (11.0592MHz crystal)
TL1 = 0xFD;
TR1 = 1; // Start timer1
SCON = 0x50; // Serial mode 1 (8-bit UART), enable reception
TI = 1; // Set transmit flag to allow printf output
}
void main(void)
{
Timer_Init();
UART_Init();
while (1)
{
printf("%d\n", cnt++); // Output counter value with newline
delay_ms(10); // Delay 10ms between outputs
}
}注4：
输入输出交互。最简单的输入，就是按键，记得加一个上拉电阻即可。
#include <reg52.h>
sbit LED = P2^0; // LED connected to P2.0 (active low)
sbit KEY = P3^2; // Button connected to P3.2 (INT0 pin, with internal pull-up)
bit led_state = 0; // LED state: 0=OFF, 1=ON
// Simple debounce delay (about 10ms @ 12MHz)
void delay_ms(unsigned int ms)
{
unsigned int i, j;
for (i = 0; i < ms; i++)
for (j = 0; j < 125; j++);
}
void main(void)
{
LED = 1; // Initial OFF (high level turns off)
led_state = 0;
while (1)
{
if (KEY == 0) // Button pressed detected (active low)
{
delay_ms(10); // Debounce delay
if (KEY == 0) // Confirm the button is actually pressed
{
led_state = ~led_state; // Toggle LED state
LED = ~led_state; // Output to LED (Note: LED is active low)
while (KEY == 0); // Wait for button release
delay_ms(5); // Release debounce
}
}
}
}