8051/2 microcontroller commonly used local communication methods UART, RS485, I2C, SPI 25AA040A read and write E2PROM 4

1. Description

PART 3 SPI (SCLK, SDO, SDI) full duplex  

SCLK clock, SDO (MOSI) data output, SDI (MISO) data input

8051SPI and I2C also need to use IO simulation

There are 4 types of SPI bus transmission:

CPOL bit, high level: 1, low level: 0

CPHA bit, edge, read first then write: 0, write first then read: 1

When transmitting, transmit the high bit first and then the low bit

The experimental program uses SPI serial bus EEPROM, 25AA040A 

process

Read data: Write the read command first, then write the read address

Write data: first latch the write address, then use the write command, write the address, and then write the data

A8 If it is a 9-bit register, valid 1, 8-bit is 0

2. Demonstration

3. Timing

Command word

Read and write timing

Write Enable

Code:

/**

* 8051/2 DEMO 3

* Commonly used local communication methods

* 1. Serial port UART, baud rate: 9600

* When connecting a device, generally only GND RX TX is connected, and Vcc is not connected to avoid power supply conflicts with the target device.

* 1.1 RS485 standard (+2V ~ +6V: 1 / -6V ~ -2V: 0)

* 1.2 RS232 standard (-15V ~ -3V: 1 / +3V ~ +15V: 0), MAX232 needs to perform level inversion before communication with MCU

* 1.3 TTL standard (2.4V--5V:1 / 0V--0.5V:0)

* 

* 2.I2C（SCL,SDA）

* 3. SPI (SCLK, SDO, SDI) full duplex

*/

#include "REG52.H"

#include

typedef unsigned char U8;

/** 

* PART 3 SPI (SCLK, SDO, SDI) full duplex  

* SCLK clock

* SDO (MOSI) data output

* SDI (MISO) data input

* 8051SPI and I2C also need to use IO simulation

* There are 4 types of SPI bus transmission:

* CPOL bit, high level: 1, low level: 0

* CPHA bit, edge, read first then write: 0, write first then read: 1

* When transmitting, transmit the high bit first and then the low bit

* 

* The experimental program uses SPI serial bus EEPROM, 25AA040A 

* process

* Read data: Write the read command first, then write the read address

* Write data: first latch the write address, then use the write command, write the address, and then write the data

* 

* A8 If it is a 9-bit register, valid 1, 8-bit is 0

**/

#define READ 0x03

#define WRITE 0x02

#define WREN 0x06

sbit SCK = P2^4;

sbit SI = P2^5;

sbit SO = P2^6;

sbit CS = P2^7;

//Serial port initialization - for printing data

void uart_init()

{ 

   SCON = 0x50;

   TMOD = 0x20; //Select timer 1

   //Install the high 8 bits and low 8 bits of the baud rate, 9600

   TH1 = 0xFD;

   TL1 = 0xFD;

   ES = 1; //Open serial port interrupt

   TR1 = 1; //Turn on timer 1

   EA = 1; // Enable general interrupt

}

//Send a character

void uart_send_char(char str)

{

   SBUF = str; //Put the string to be sent into the buffer

   while(TI==0); //Wait for sending to complete

   TI=0; // Clear the send interrupt flag

}

//Serial port interrupt service processing 

void uart_handle() interrupt 4

{ 

}

//Write 1 byte

void spi_write(U8 dat)

{

  U8 i=0;

  for(i=0;i<8;i++)

  {

     SCK = 0; //Read SI data when a rising edge occurs

     // Take the data bits in sequence and give them to SI

     SI=given>>7;

  that=that<<1;

     SCK = 1;

  }

}

//After reading the rising edge, read the data

U8 spi_read()

{

  U8 i=0;

  U8 that=0;

  for(i=0;i<8;i++)

  {

      SCK = 0;

      SCK = 1;

      //Put the data bits into SO in sequence

      dat <<= 1;

that|=SO;

  }

  return that;

}

//Read eeprom operation

U8 spi_device_read(U8 addr)

{ 

   U8 that=0;

   CS = 0;

   spi_write(READ);

   spi_write(addr);

   that = spi_read();

   CS = 1; // Pull CS back to high level after reading

   return that;

}

void delay5ms() //Error -0.000000000001us

{

    unsigned char a,b;

    for(b=15;b>0;b--)

        for(a=152;a>0;a--);

}

//Write eeprom operation

void spi_device_write(U8 addr,U8 dat){

   //Write ready

   CS = 0;

   spi_write(WREN); 

   CS = 1; //pull high

   CS = 0;

   spi_write(WRITE); //Use write command

   spi_write(addr);

   spi_write(dat);

   //Whether the write is successful or not, delay 5ms

   delay5ms();

   CS = 1;

}

void delay1s() //error 0us

{

    unsigned char a,b,c;

    for(c=167;c>0;c--)

        for(b=171;b>0;b--)

            for(a=16;a>0;a--);

}

void main()

{

   U8 res1;

   //Initialize the serial port to display the data to the serial port

   uart_init();

   //Write data, address 1, write value 2

   delay1s();

   spi_device_write(1,0x11);

   delay1s();

   res1 = spi_device_read(1);

   //Send to the serial port

   uart_send_char(res1);

   while (1){

   }

}