From 0503e52271f331086ded79ebd92221ffe6b3c5c1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jo=C3=A3o=20Magalh=C3=A3es?= <joamag@gmail.com>
Date: Sat, 25 Mar 2023 15:23:24 +0000
Subject: [PATCH] feat: initial channel4 implementation code
---
src/apu.rs | 32 +++++++++++++++++++++++++++++++-
1 file changed, 31 insertions(+), 1 deletion(-)
diff --git a/src/apu.rs b/src/apu.rs
index 4dac0686..b7f69143 100644
--- a/src/apu.rs
+++ b/src/apu.rs
@@ -62,6 +62,9 @@ pub struct Apu {
ch4_timer: i16,
ch4_output: u8,
ch4_length_timer: u8,
+ ch4_pace: u8,
+ ch4_direction: u8,
+ ch4_volume: u8,
ch4_output_level: u8,
ch4_wave_length: u16,
ch4_length_stop: bool,
@@ -128,6 +131,9 @@ impl Apu {
ch4_timer: 0,
ch4_output: 0,
ch4_length_timer: 0x0,
+ ch4_pace: 0x0,
+ ch4_direction: 0x0,
+ ch4_volume: 0x0,
ch4_output_level: 0x0,
ch4_wave_length: 0x0,
ch4_length_stop: false,
@@ -140,6 +146,10 @@ impl Apu {
/// to be used in channel 3 audio
wave_ram: [0u8; 16],
+ /// The rate at which audio samples are going to be
+ /// taken, ideally this value should be aligned with
+ /// the sampling rate of the output device. A typical
+ /// sampling rate would be of 44.1kHz.
sampling_rate,
/// Internal sequencer counter that runs at 512Hz
@@ -361,6 +371,26 @@ impl Apu {
self.ch3_enabled |= value & 0x80 == 0x80;
}
+ // 0xFF20 — NR41: Channel 4 length timer
+ 0xff20 => {
+ self.ch4_length_timer = value & 0x3f;
+ }
+ // 0xFF21 — NR42: Channel 4 volume & envelope
+ 0xff21 => {
+ self.ch4_pace = value & 0x07;
+ self.ch4_direction = (value & 0x08) >> 3;
+ self.ch4_volume = (value & 0xf0) >> 4;
+ }
+ // 0xFF22 — NR43: Channel 4 frequency & randomness
+ 0xff22 => {
+ //@TODO need to implement this one!
+ }
+ // 0xFF23 — NR44: Channel 4 control
+ 0xff23 => {
+ self.ch4_length_stop |= value & 0x40 == 0x40;
+ self.ch4_enabled |= value & 0x80 == 0x80;
+ }
+
// 0xFF30-0xFF3F — Wave pattern RAM
0xff30..=0xff3f => {
self.wave_ram[addr as usize & 0x000f] = value;
@@ -371,7 +401,7 @@ impl Apu {
}
pub fn output(&self) -> u8 {
- self.ch1_output + self.ch2_output + self.ch3_output
+ self.ch1_output + self.ch2_output + self.ch3_output + self.ch4_output
}
pub fn audio_buffer(&self) -> &VecDeque<u8> {
--
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