Page 214 - The Unofficial Guide to Lego Mindstorms Robots

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Sound (rom/sound.h and direct-sound.h)

You can play one of the RCX's built-in ''system" sounds with the following function:

void sound_system(unsigned nr)
This function plays one of the system sounds of the RCX. The nr parameter describes the sound; it can be any of the values
shown in Table 10-1.

Table 10-1. sound_system() Sound Numbers

Sound Number Description

0 Short beep

1 Two medium beeps

2 Descending arpeggio

3 Ascending arpeggio

4 Long low note

a
5 Quick ascending arpeggio (same as 3 but f ster)
F urthermore, you can play any sound you want using this function:

void ds_play(unsigned char ∗sample, unsigned length)

This function plays the sound data described by sample, using length bytes of data. The sample data should be 1 bit, 8
k Hz data.

Unfortunately, neither sound _system() nor ds_play() works in the March 30, 1999 build of legOS 0.1.7

.

Other Goodies

legOS has a grab-bag of other intere sting features. In this section, these functions are organized by the header file in which
r
a
they e defined.

In stdlib.h

legOS supports a simple random numb er generator with the following two functions:

long int random(void)
This function returns a pseudorandom number.

void srandom(unsigned int seed)
Use this function to provide a new seed for th e pseudorandom number generator.