Random Number

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Overview
Storage
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BLE

This library obtains random numbers. True random numbers can be obtained from ESP32 as shown in the sample.

randomSeed

Description

randomSeed() initializes the pseudo-random number generator, causing it to start at an arbitrary point in its random sequence. This sequence, while very long, and random, is always the same.

Syntax

randomSeed(unsigned int seed)

Parameters

seed: A number to generate the seed

Returns

None

random

Description

Obtains the random numbers. Always call the randomSeed function before using this function.

Syntax

long random(long min_num, long max_num)

Parameters

min_num: Lower bound of the random value, inclusive (optional)
max_num: Upper bound of the random value, exclusive (optional)

Returns

A random number (long)

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This example outputs a random number between 0 and 99 in 100ms intervals via serial communications.

#include <Arduino.h>
#define INTERVAL 100
    
void setup()
{
    Serial.begin(9600);
    randomSeed(millis());
}
    
void loop()
{
    Serial.println( random(0, 100) );
    delay(INTERVAL);
}

Get a 32-bit true random number.

#include <Arduino.h>
#include <Wire.h>
#define ESP32_I2C_ADDR    0x28
    
void setup() {
    Serial.begin(9600);
    
    Wire.setFrequency(150000);
    Wire.begin();
    
    pinMode(PIN_ESP_EN, OUTPUT);
    pinMode(PIN_ESP_IO0, OUTPUT);
    pinMode(PIN_SW0, INPUT);
    pinMode(PIN_SW1, INPUT);
    
    digitalWrite(PIN_ESP_IO0, HIGH);
    delay(100);
    digitalWrite(PIN_ESP_EN, HIGH);
    delay(1000);
    
}
    
void loop() {
    Wire.beginTransmission(ESP32_I2C_ADDR);
    Wire.write(0);
    Wire.endTransmission();
    
    uint32_t rand;
    Wire.requestFrom(ESP32_I2C_ADDR, 4);
    rand = Wire.read();
    rand <<= 8;
    rand += Wire.read();
    rand <<= 8;
    rand += Wire.read();
    rand <<= 8;
    rand += Wire.read();
    Serial.print(rand, HEX);         // print the character
    Serial.println();
    delay(100);
}