13-ESP8266 SDK Development Fundamentals Introduction--The host computer serial port controls the duty cycle of Wi-Fi output PWM, IEEE754 protocol

https://www.cnblogs.com/yangfengwu/p/11100552.html

In this section, let the host computer control the PWM duty cycle signal output by the Wi-Fi pin, and the brightness of the lamp can be controlled by the host computer.

You can extend the program to control the rotation angle of the servo

Double click

textBox3.Text = trackBar1.Value.ToString();//Display the value of the current slider

Then stipulate the agreement, pay attention to the versatility of the project for everyone in the future, and use it for data transmission.

Talk about a knowledge point

How do you transmit decimal data? How do you transmit floating-point data? Baidu download IEEE754

Take a look at the magical use of it for data conversion

I said directly

Suppose you want to send 220.5

this way

Let's create a new data_dispose.h file

To prevent others from using my source code to compile in C++

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typedef union Resolve//Analysis of data 
{ 
    char Data_Table[4];//16 hexadecimal four-byte representation 
    float DataF;//Floating point type 
    long DataInt;//Signed integer 
    unsigned long DatauInt;//Unsigned integer 
} ResolveData;

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See now to use

Suppose I collected the instrumentation. The instrumentation is the 220.5 floating-point data sent by the IEEE754 specification. 0x43 0x5C 0x80 0x00

I now need to convert to 220.5

Pay attention to one thing 0x43 0x5C 0x80 0x00 is the high-order data first

For example: 259

Converted to hexadecimal, it is 0x01 0x03, so the sorting is high order first

How to convert the hexadecimal number to 259, that is, 0x01==1, multiplying 1 by 2 to the 8th power, and adding 0x03 to the power of 3.

1*256 + 3 = 259

If the calculation is done, the memory is stored like this

Say a noun: big-endian mode

If the high bit of data is stored in the low bit of the storage address, the low bit of data is stored in the high bit of the storage address -----Name: Big-endian mode

The opposite is little endian

The low bit of data is stored in the low bit of the storage address The high bit of data is stored in the high bit of the storage address -----Name: Little-endian mode

If you have made instruments and meters, or used instruments and meters, you should know that they are often used in industry

Then remind

51 single-chip microcomputer storage data is big-endian mode

STM32 is little-endian

Computer: Little-endian mode

Phone: It seems to be in big-endian mode...forgot

The 8266 little-endian mode we use

Someone may ask, how do you see it in detail...

Look at

First remember

Pay attention to one thing 0x43 0x5C 0x80 0x00 is the high-order data in the front, the low-order data in the back

I tested it just now, and the official printf does not support printing floating point numbers...

So I wrote a printf function myself

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void sendstring(unsigned char *string)//here *string is equivalent to an array 
{ 
    while(*string!='\0')//Determine whether the end of the string is 
        reached 
    { USART_SendData(UART0, *string); 
        string++; 
    } 
} 

void uart_printf(const char *fmt,...)//Use the same as printf 
{ 
    va_list ap; 
    char string[200];//Cache, if you send more than this number, please increase 
    va_start(ap,fmt); 
    vsprintf(string,fmt,ap);//The sprintf function can also be used here, the usage is similar, just a little modification, here 
    sendstring(string); 
    va_end(ap); 
}