random

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Description

Generate a pseudo-random number within [0;32767]

Notes:

• the used pseudo random number generator by default starts with a fixed seed of 1. To randomize the result, call randomSeed() with a random parameter, e.g. from a floating ADC input (see example)
• randomIn() can be used to generate a random number in a specified range

Inclusion

• defined in misc.h
• auto-loaded in main_general.h
• no #define required

Syntax

r = random()

Parameters

• input:

  • none

• output:

  • none

Returns

• pseudo-random numbers within [0;RAND_MAX], with RAND_MAX=32767 for both SDCC and Cosmic

Example Code

The below code makes pin PD0 (=LED on STM8S Discovery Board) OUTPUT and toggles it HIGH and LOW with random delay. Note that without random seed via randomSeed(), the sequence is always the same.

#include "main_general.h"   // board-independent main
    
void setup()
{
  pinMode(&PORT_D, 0, OUTPUT);        // configure PD0 as output
}

void loop()
{
  // toggle PD0
  pinToggle(&PORT_D, 0);

  // wait random delay between 50..200ms
  delay(50 + random() % 150);
}

Relevant Tutorial

• tbd

Notes and Warnings

• for implementation details and limitations see compiler documentation for rand()

See also

• randomSeed()
• randomIn()