organ.c File Reference

Implementation of tone generation functions for electronic organ. More...

#include "includes/CPU.h"
#include <avr/io.h>
#include <util/delay.h>
#include "includes/organ.h"
#include "includes/pinDefines.h"

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Functions
void	playNote (uint16_t half_us, uint16_t duration_ms)
	Generates a musical tone with specific duration.
void	rest (uint16_t duration)

Detailed Description

Implementation of tone generation functions for electronic organ.

Author

Roybel Carbonell Camejo

Date

2026-04-28

This file contains the implementation of functions required to generate musical tones using a piezoelectric buzzer.

Definition in file organ.c.

Function Documentation

playNote()

void playNote	(	uint16_t	half_us,
		uint16_t	duration_ms
	)

Generates a musical tone with specific duration.

Play a musical tone.

Parameters

[in]	half_us	Half period of the square wave in microseconds (1/(2*frequency))
[in]	duration_ms	Total note duration in milliseconds

This function generates a square wave on the buzzer pin to produce a musical tone. The tone is generated using the following formula:

• Frequency (Hz) = 1,000,000 / (2 * half_us)
• Total cycles = (frequency * duration_ms) / 1000

Algorithm:

The function toggles the buzzer pin between HIGH and LOW, with delays equal to the specified half period, thus generating a perfect square wave.

Example:

// Generate A4 (440 Hz) for 500 ms
// half_us = 1,000,000/(2*440) = 1136 us
play_note(1136, 500);

Note

The cycle calculation is performed as: cycles = (500000 / half_us) * duration_ms / 1000 This formula avoids integer overflow.

Warning

This function uses _delay_us() which is NOT accurate for delays > 768 us at 16 MHz. For half_us > 768, consider using hardware timers.

Delays are blocking; no other tasks can execute during note playback.

Precondition

The BUZZER_PIN must be configured as output on BUZZER_PORT before calling this function.

Postcondition

After playing the note, there is an additional 30ms delay to prevent "clicks" between notes.

See also

timer_generate_tone() For non-blocking implementation

play_song() For playing complete melodies

@bugs For very small half_us (< 10), the generated frequency may be inaccurate due to loop overhead.

Todo:

Implement hardware timer version for non-blocking playback

Add volume control using PWM modulation

Definition at line 66 of file organ.c.

References BUZZER_PIN, and BUZZER_PORT.

Referenced by main(), and play_twinkle_little_star().

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rest()

void rest

(

uint16_t

duration

)

Definition at line 92 of file organ.c.

Referenced by main().

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