How to generate random numbers using a single chip microcomputer

There are many random numbers in the application of single-chip microcomputers. Of course, there are many ways to generate random numbers. One of them is to use the single-chip microcomputer timer to take out the unknown timer THX and TLX values, and then calculate to get a random value within a specified range. This approach is also feasible. Or you can write a random number table in advance and then take the data. This is also possible.

The function that generates random numbers in KEIL is indeed rand(), but the header file is stdlib.h, not time.h. C language provides some library functions to generate random numbers. There are three common random number generators in C language, namely rand function, random function, and randomize function; however, the rand function does not generate a true random number, but a pseudo-random number, which is a coefficient calculated based on a number, called a seed, and a recursive formula. When this series of numbers is very large, it conforms to the normal distribution, which is equivalent to generating random numbers, but this is not a true random number. When the computer is turned on normally, the value of this seed is fixed, unless the system is damaged. In order to change the value of this seed, C provides the srand() function, whose prototype is void srand(int a); before calling the rand function to generate random numbers, you must first use srand() to set the random number seed. If the random number seed is not set, rand() will automatically set the random number seed to 1 when it is called. Generally, the for statement is used to set the number of seeds.

Two methods of generating random numbers using single chip microcomputer

Method 1: Timer directly takes random values

Each time a button is pressed, a random number is generated. This random number actually takes out the value of the timer and cannot be considered absolutely random. Method 2 is the real random number.

Method 2: Use a timer plus the rand() random function to implement

After the microcontroller is powered on, a button is pressed to start the random number fetching. If the microcontroller fetches random numbers immediately after powering on, the random number fetching result will be the same each time it is powered on. Then a non-repeating random number from 0 to 9 is generated. The program uses a loop to determine whether it is the same as the previously fetched random number. If it is the same, the program will enter and fetch the random number next time. If it is different, the program will store it in the array.