Added USB microphone example

workflow: add build pipeline

.github/workflows/build.yml

@@ -0,0 +1,39 @@
+name: Build USB examples
+
+on:
+  push:
+    branches: ["develop"]
+    paths-ignore:
+      - 'README.md'
+  pull_request:
+    branches: ["develop"]
+    paths-ignore:
+      - 'README.md'
+
+jobs:
+  build:
+    strategy:
+      matrix:
+        example: [
+            "mass-storage",
+            "usb-microphone",
+            "usb-speaker",
+            "usb-video"
+        ]
+    runs-on: ubuntu-latest
+    container: devkitpro/devkitarm:20241104
+    name: Build with Docker using devkitARM
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v4
+        with:
+          submodules: recursive
+      - name: Build example
+        run: |
+            cd examples/${{ matrix.example }}
+            make
+      - name: Publish build to GH Actions
+        uses: actions/upload-artifact@v4
+        with:
+          path: examples/${{ matrix.example }}/${{ matrix.example }}.nds
+          name: ${{ matrix.example }}

.github/workflows/release.yml

@@ -0,0 +1,38 @@
+name: Build USB examples release
+
+on:
+  release:
+    types: [published]
+
+jobs:
+  build:
+    strategy:
+      matrix:
+        example: [
+            "mass-storage",
+            "usb-microphone",
+            "usb-speaker",
+            "usb-video"
+        ]
+    runs-on: ubuntu-latest
+    container: devkitpro/devkitarm:20241104
+    name: Build with Docker using devkitARM
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v4
+        with:
+          submodules: recursive
+      - name: Build example
+        run: |
+            cd examples/${{ matrix.example }}
+            make
+      - name: Publish build to GH Actions
+        uses: actions/upload-artifact@v4
+        with:
+          path: examples/${{ matrix.example }}/${{ matrix.example }}.nds
+          name: ${{ matrix.example }}
+      - name: Release
+        uses: softprops/action-gh-release@v2
+        with:
+          files: |
+            examples/${{ matrix.example }}/${{ matrix.example }}.nds

README.md

@@ -3,6 +3,8 @@ This repository contains examples of using the DSpico USB port from a DS applica
 
 The `examples` folder contains the following examples:
 - mass-storage - Allows access to the DSpico micro SD card over USB
+- usb-microphone - Makes the DSi/3DS work as a USB microphone for your PC
+    - Note: does not work with regular DS devices currently
 - usb-speaker - Makes the DS/DSi/3DS work as a USB speaker for your PC
 - usb-video - Allows to use the camera of your DSi or 3DS on your PC via USB
 

examples/usb-microphone/Makefile

@@ -0,0 +1,61 @@
+#---------------------------------------------------------------------------------
+.SUFFIXES:
+#---------------------------------------------------------------------------------
+ifeq ($(strip $(DEVKITARM)),)
+$(error "Please set DEVKITARM in your environment. export DEVKITARM=<path to>devkitARM")
+endif
+
+export TARGET	:=	$(shell basename $(CURDIR))
+export TOPDIR	:=	$(CURDIR)
+
+# specify a directory which contains the nitro filesystem
+# this is relative to the Makefile
+NITRO_FILES	:=
+
+# These set the information text in the nds file
+GAME_TITLE     := USB Microphone Example
+GAME_SUBTITLE1 := DSpico
+GAME_SUBTITLE2 := LNH team
+GAME_ICON	   := icon.bmp
+
+include $(DEVKITARM)/ds_rules
+
+.PHONY: checklibtwl checkarm7 checkarm9 clean
+
+#---------------------------------------------------------------------------------
+# main targets
+#---------------------------------------------------------------------------------
+all: checklibtwl checkarm7 checkarm9 $(TARGET).nds
+
+#---------------------------------------------------------------------------------
+checklibtwl:
+	$(MAKE) -C ../../libs/libtwl/libtwl7
+	$(MAKE) -C ../../libs/libtwl/libtwl9
+
+#---------------------------------------------------------------------------------
+checkarm7: checklibtwl
+	$(MAKE) -C arm7
+
+#---------------------------------------------------------------------------------
+checkarm9: checklibtwl
+	$(MAKE) -C arm9
+
+#---------------------------------------------------------------------------------
+$(TARGET).nds	: $(NITRO_FILES) arm7/$(TARGET).elf arm9/$(TARGET).elf
+	ndstool	-c $(TARGET).nds -7 arm7/$(TARGET).elf -9 arm9/$(TARGET).elf \
+	-b $(GAME_ICON) "$(GAME_TITLE);$(GAME_SUBTITLE1);$(GAME_SUBTITLE2)" \
+	$(_ADDFILES)
+
+#---------------------------------------------------------------------------------
+arm7/$(TARGET).elf:
+	$(MAKE) -C arm7
+
+#---------------------------------------------------------------------------------
+arm9/$(TARGET).elf:
+	$(MAKE) -C arm9
+
+#---------------------------------------------------------------------------------
+clean:
+	$(MAKE) -C arm9 clean
+	$(MAKE) -C arm7 clean
+	rm -f $(TARGET).nds $(TARGET).arm7 $(TARGET).arm9

examples/usb-microphone/arm7/Makefile

@@ -0,0 +1,137 @@
+#---------------------------------------------------------------------------------
+.SUFFIXES:
+#---------------------------------------------------------------------------------
+ifeq ($(strip $(DEVKITARM)),)
+$(error "Please set DEVKITARM in your environment. export DEVKITARM=<path to>devkitARM")
+endif
+
+include $(DEVKITARM)/ds_rules
+
+#---------------------------------------------------------------------------------
+# BUILD is the directory where object files & intermediate files will be placed
+# SOURCES is a list of directories containing source code
+# INCLUDES is a list of directories containing extra header files
+# DATA is a list of directories containing binary files
+# all directories are relative to this makefile
+#---------------------------------------------------------------------------------
+BUILD		:=	build
+SOURCES		:=	source \
+				../common/ipc \
+				source/ipcServices \
+				../../../platform \
+				../../../libs/tinyusb/src \
+				../../../libs/tinyusb/src/device \
+				../../../libs/tinyusb/src/class/audio \
+				../../../libs/tinyusb/src/class/cdc \
+				../../../libs/tinyusb/src/class/msc \
+				../../../libs/tinyusb/src/common
+INCLUDES	:=	source include build ../common ../../../libs/tinyusb/src ../../../platform
+DATA		:=
+ 
+#---------------------------------------------------------------------------------
+# options for code generation
+#---------------------------------------------------------------------------------
+ARCH	:=	-marm -mthumb-interwork -DLIBTWL_ARM7 -DARM7
+
+CFLAGS	:=	-g -Wall -O2\
+		-mcpu=arm7tdmi -mtune=arm7tdmi -fomit-frame-pointer\
+		-ffunction-sections -fdata-sections\
+		-ffast-math \
+		$(ARCH)
+
+CFLAGS	+=	$(INCLUDE)
+CXXFLAGS	:=	$(CFLAGS) -std=gnu++23 -Wno-volatile -fno-rtti -fno-exceptions -fno-threadsafe-statics\
+				-Wsuggest-override -Werror=suggest-override
+
+
+ASFLAGS	:=	-g $(ARCH)
+LDFLAGS	=	-specs=../dldi_ds_arm7.specs -g $(ARCH) -Wl,--nmagic -Wl,-Map,$(notdir $*).map,--gc-sections -ffunction-sections -fdata-sections
+
+LIBS	:=	-ltwl7 -lnds7
+
+#---------------------------------------------------------------------------------
+# list of directories containing libraries, this must be the top level containing
+# include and lib
+#---------------------------------------------------------------------------------
+LIBDIRS	:=	$(LIBNDS) $(CURDIR)/../../../libs/libtwl/libtwl7 $(CURDIR)/../../../libs/libtwl/common
+ 
+  
+#---------------------------------------------------------------------------------
+# no real need to edit anything past this point unless you need to add additional
+# rules for different file extensions
+#---------------------------------------------------------------------------------
+ifneq ($(BUILD),$(notdir $(CURDIR)))
+#---------------------------------------------------------------------------------
+ 
+export ARM7ELF	:=	$(CURDIR)/$(TARGET).elf
+export DEPSDIR	:=	$(CURDIR)/$(BUILD)
+
+export VPATH	:=	$(foreach dir,$(SOURCES),$(CURDIR)/$(dir))
+ 
+CFILES		:=	$(foreach dir,$(SOURCES),$(notdir $(wildcard $(dir)/*.c)))
+CPPFILES	:=	$(foreach dir,$(SOURCES),$(notdir $(wildcard $(dir)/*.cpp)))
+SFILES		:=	$(foreach dir,$(SOURCES),$(notdir $(wildcard $(dir)/*.s)))
+BINFILES	:=	$(foreach dir,$(DATA),$(notdir $(wildcard $(dir)/*.*)))
+ 
+export OFILES	:=	$(addsuffix .o,$(BINFILES)) \
+			$(CPPFILES:.cpp=.o) $(CFILES:.c=.o) $(SFILES:.s=.o)
+ 
+export INCLUDE	:=	$(foreach dir,$(INCLUDES),-I$(CURDIR)/$(dir)) \
+			$(foreach dir,$(LIBDIRS),-I$(dir)/include) \
+			-I$(CURDIR)/$(BUILD)
+ 
+export LIBPATHS	:=	$(foreach dir,$(LIBDIRS),-L$(dir)/lib)
+
+#---------------------------------------------------------------------------------
+# use CXX for linking C++ projects, CC for standard C
+#---------------------------------------------------------------------------------
+ifeq ($(strip $(CPPFILES)),)
+#---------------------------------------------------------------------------------
+	export LD	:=	$(CC)
+#---------------------------------------------------------------------------------
+else
+#---------------------------------------------------------------------------------
+	export LD	:=	$(CXX)
+#---------------------------------------------------------------------------------
+endif
+#---------------------------------------------------------------------------------
+
+.PHONY: $(BUILD) clean
+ 
+#---------------------------------------------------------------------------------
+$(BUILD):
+	@[ -d $@ ] || mkdir -p $@
+	@$(MAKE) --no-print-directory -C $(BUILD) -f $(CURDIR)/Makefile
+ 
+#---------------------------------------------------------------------------------
+clean:
+	@echo clean ...
+	@rm -fr $(BUILD) *.elf
+ 
+ 
+#---------------------------------------------------------------------------------
+else
+ 
+DEPENDS	:=	$(OFILES:.o=.d)
+ 
+#---------------------------------------------------------------------------------
+# main targets
+#---------------------------------------------------------------------------------
+$(ARM7ELF)	:	$(OFILES)
+	@echo linking $(notdir $@)
+	@$(LD)  $(LDFLAGS) $(OFILES) $(LIBPATHS) $(LIBS) -o $@
+
+
+#---------------------------------------------------------------------------------
+# you need a rule like this for each extension you use as binary data 
+#---------------------------------------------------------------------------------
+%.bin.o	:	%.bin
+#---------------------------------------------------------------------------------
+	@echo $(notdir $<)
+	@$(bin2o)
+
+-include $(DEPENDS)
+ 
+#---------------------------------------------------------------------------------------
+endif
+#---------------------------------------------------------------------------------------

examples/usb-microphone/arm7/dldi_ds_arm7.ld

@@ -0,0 +1,232 @@
+/*--------------------------------------------------------------------------------
+	This Source Code Form is subject to the terms of the Mozilla Public License,
+	v. 2.0. If a copy of the MPL was not distributed with this file, You can
+	obtain one at https://mozilla.org/MPL/2.0/.
+--------------------------------------------------------------------------------*/
+OUTPUT_FORMAT("elf32-littlearm", "elf32-bigarm", "elf32-littlearm")
+OUTPUT_ARCH(arm)
+ENTRY(_start)
+
+
+PHDRS {
+	crt0  PT_LOAD FLAGS(7);
+	arm7  PT_LOAD FLAGS(7);
+	arm7i PT_LOAD FLAGS(0x100007);
+}
+
+
+MEMORY {
+	ewram  : ORIGIN = 0x02380000, LENGTH = 12M - 512K
+	rom    : ORIGIN = 0x08000000, LENGTH = 32M
+	iwram  : ORIGIN = 0x037fc000, LENGTH = (96K - 16K)
+
+	twl_ewram : ORIGIN = 0x02e80000, LENGTH = 512K - 64K
+	twl_iwram : ORIGIN = 0x03000000, LENGTH = 256K
+}
+
+__iwram_start	=	ORIGIN(iwram);
+__iwram_top	=	ORIGIN(iwram)+ LENGTH(iwram);
+
+__sp_irq	=	__iwram_top - 0x100;
+__sp_svc	=	__sp_irq - 0x100;
+__sp_usr	=	__sp_svc - 0x100;
+
+__irq_flags	=	0x04000000 - 8;
+__irq_flagsaux	=	0x04000000 - 0x40;
+__irq_vector	=	0x04000000 - 4;
+
+SECTIONS
+{
+
+	.twl :
+	{
+		__arm7i_lma__ = LOADADDR(.twl);
+		__arm7i_start__ = .;
+		*(.twl)
+		*.twl*(.text .stub .text.* .gnu.linkonce.t.*)
+		*.twl*(.rodata)
+		*.twl*(.roda)
+		*.twl*(.rodata.*)
+		*.twl*(.data)
+		*.twl*(.data.*)
+		*.twl*(.gnu.linkonce.d*)
+		. = ALIGN(4);
+		__arm7i_end__ = .;
+	} >twl_iwram AT>twl_ewram :arm7i
+
+	.twl_bss ALIGN(4) (NOLOAD) :
+	{
+		__twl_bss_start__ = .;
+		*(.twl_bss)
+		*.twl.*(.dynbss)
+		*.twl.*(.gnu.linkonce.b*)
+		*.twl.*(.bss*)
+		*.twl.*(COMMON)
+		. = ALIGN(4);
+		__twl_bss_end__ = .;
+	} >twl_iwram :NONE
+
+	.crt0	:
+	{
+		KEEP (*(.crt0))
+		. = ALIGN(4);  /* REQUIRED. LD is flaky without it. */
+	} >ewram :crt0
+
+	.text :
+	{
+		__arm7_lma__ = LOADADDR(.text);
+		__arm7_start__ = .;
+		KEEP (*(SORT_NONE(.init)))
+		*(.plt)
+		*(.text .stub .text.* .gnu.linkonce.t.*)
+		KEEP (*(.text.*personality*))
+		/* .gnu.warning sections are handled specially by elf32.em.  */
+		*(.gnu.warning)
+		*(.glue_7t) *(.glue_7) *(.vfp11_veneer)
+		. = ALIGN(4);  /* REQUIRED. LD is flaky without it. */
+	} >iwram AT>ewram :arm7
+
+	.fini           :
+	{
+		KEEP (*(.fini))
+	} >iwram AT>ewram
+
+	.rodata :
+	{
+		*(.rodata)
+		*all.rodata*(*)
+		*(.roda)
+		*(.rodata.*)
+		*(.gnu.linkonce.r*)
+		SORT(CONSTRUCTORS)
+		. = ALIGN(4);   /* REQUIRED. LD is flaky without it. */
+	} >iwram AT>ewram
+
+	.ARM.extab   : { *(.ARM.extab* .gnu.linkonce.armextab.*) } >iwram AT>ewram
+
+	.ARM.exidx   : {
+		__exidx_start = .;
+		*(.ARM.exidx* .gnu.linkonce.armexidx.*)
+		__exidx_end = .;
+	 } >iwram AT>ewram
+
+/* Ensure the __preinit_array_start label is properly aligned.  We
+   could instead move the label definition inside the section, but
+   the linker would then create the section even if it turns out to
+   be empty, which isn't pretty.  */
+	.preinit_array     : {
+		. = ALIGN(32 / 8);
+		PROVIDE (__preinit_array_start = .);
+		KEEP (*(.preinit_array))
+		PROVIDE (__preinit_array_end = .);
+	} >iwram AT>ewram
+
+	.init_array     : {
+		PROVIDE (__init_array_start = .);
+		KEEP (*(.init_array))
+		PROVIDE (__init_array_end = .);
+	} >iwram AT>ewram
+
+	.fini_array     : {
+		PROVIDE (__fini_array_start = .);
+		KEEP (*(.fini_array))
+		PROVIDE (__fini_array_end = .);
+	} >iwram AT>ewram
+
+	.ctors :
+	{
+	/* gcc uses crtbegin.o to find the start of the constructors, so
+		we make sure it is first.  Because this is a wildcard, it
+		doesn't matter if the user does not actually link against
+		crtbegin.o; the linker won't look for a file to match a
+		wildcard.  The wildcard also means that it doesn't matter which
+		directory crtbegin.o is in.  */
+		KEEP (*crtbegin.o(.ctors))
+		KEEP (*(EXCLUDE_FILE (*crtend.o) .ctors))
+		KEEP (*(SORT(.ctors.*)))
+		KEEP (*(.ctors))
+		. = ALIGN(4);   /* REQUIRED. LD is flaky without it. */
+	} >iwram AT>ewram
+
+	.dtors :
+	{
+		KEEP (*crtbegin.o(.dtors))
+		KEEP (*(EXCLUDE_FILE (*crtend.o) .dtors))
+		KEEP (*(SORT(.dtors.*)))
+		KEEP (*(.dtors))
+		. = ALIGN(4);   /* REQUIRED. LD is flaky without it. */
+	} >iwram AT>ewram
+
+	.eh_frame :
+	{
+		KEEP (*(.eh_frame))
+		. = ALIGN(4);   /* REQUIRED. LD is flaky without it. */
+	} >iwram AT>ewram
+
+	.gcc_except_table :
+	{
+		*(.gcc_except_table)
+		. = ALIGN(4);   /* REQUIRED. LD is flaky without it. */
+	} >iwram AT>ewram
+	.jcr            : { KEEP (*(.jcr)) } >iwram AT>ewram
+	.got            : { *(.got.plt) *(.got) } >iwram AT>ewram
+
+	.data ALIGN(4) : 	{
+		__data_start = ABSOLUTE(.);
+		*(.data)
+		*(.data.*)
+		*(.gnu.linkonce.d*)
+		CONSTRUCTORS
+		. = ALIGN(4);
+		__data_end = ABSOLUTE(.) ;
+	} >iwram AT>ewram
+
+	.bss ALIGN(4) (NOLOAD) :
+	{
+		__arm7_end__ = .;
+		__bss_start = ABSOLUTE(.);
+		__bss_start__ = ABSOLUTE(.);
+		*(.dynbss)
+		*(.gnu.linkonce.b*)
+		*(.bss*)
+		*(COMMON)
+		. = ALIGN(4);    /* REQUIRED. LD is flaky without it. */
+		__bss_end__ = ABSOLUTE(.);
+		__end__ = ABSOLUTE(.);
+	} >iwram
+
+	/* Stabs debugging sections.  */
+	.stab 0 : { *(.stab) }
+	.stabstr 0 : { *(.stabstr) }
+	.stab.excl 0 : { *(.stab.excl) }
+	.stab.exclstr 0 : { *(.stab.exclstr) }
+	.stab.index 0 : { *(.stab.index) }
+	.stab.indexstr 0 : { *(.stab.indexstr) }
+	.comment 0 : { *(.comment) }
+	/*	DWARF debug sections.
+		Symbols in the DWARF debugging sections are relative to the beginning
+		of the section so we begin them at 0.  */
+	/* DWARF 1 */
+	.debug          0 : { *(.debug) }
+	.line           0 : { *(.line) }
+	/* GNU DWARF 1 extensions */
+	.debug_srcinfo  0 : { *(.debug_srcinfo) }
+	.debug_sfnames  0 : { *(.debug_sfnames) }
+	/* DWARF 1.1 and DWARF 2 */
+	.debug_aranges  0 : { *(.debug_aranges) }
+	.debug_pubnames 0 : { *(.debug_pubnames) }
+	/* DWARF 2 */
+	.debug_info     0 : { *(.debug_info) }
+	.debug_abbrev   0 : { *(.debug_abbrev) }
+	.debug_line     0 : { *(.debug_line) }
+	.debug_frame    0 : { *(.debug_frame) }
+	.debug_str      0 : { *(.debug_str) }
+	.debug_loc      0 : { *(.debug_loc) }
+	.debug_macinfo  0 : { *(.debug_macinfo) }
+	/* SGI/MIPS DWARF 2 extensions */
+	.debug_weaknames 0 : { *(.debug_weaknames) }
+	.debug_funcnames 0 : { *(.debug_funcnames) }
+	.debug_typenames 0 : { *(.debug_typenames) }
+	.debug_varnames  0 : { *(.debug_varnames) }
+	/* These must appear regardless of  .  */
+}

examples/usb-microphone/arm7/dldi_ds_arm7.specs

@@ -0,0 +1,8 @@
+%rename link                old_link
+
+*link:
+%(old_link) -T ../dldi_ds_arm7.ld%s --gc-sections --no-warn-rwx-segments
+
+*startfile:
+ds_arm7_crt0%O%s crti%O%s crtbegin%O%s
+

examples/usb-microphone/arm7/source/Arm7State.h

@@ -0,0 +1,8 @@
+#pragma once
+
+/// @brief Enum representing the arm7 state.
+enum class Arm7State
+{
+    Idle,
+    ExitRequested
+};

examples/usb-microphone/arm7/source/ExitMode.h

@@ -0,0 +1,10 @@
+#pragma once
+
+/// @brief Enum representing the exit mode of launcher.
+enum class ExitMode
+{
+    /// @brief Reset the system (DSi mode only).
+    Reset,
+    /// @brief Power off the system.
+    PowerOff
+};

examples/usb-microphone/arm7/source/common.h

@@ -0,0 +1,5 @@
+#pragma once
+#include <nds.h>
+#include <libtwl/rtos/rtosMutex.h>
+
+extern rtos_mutex_t gCardMutex;

examples/usb-microphone/arm7/source/main.cpp

@@ -0,0 +1,197 @@
+#include "common.h"
+#include <libtwl/rtos/rtosIrq.h>
+#include <libtwl/rtos/rtosThread.h>
+#include <libtwl/rtos/rtosEvent.h>
+#include <libtwl/sound/soundChannel.h>
+#include <libtwl/timer/timer.h>
+#include <libtwl/sound/sound.h>
+#include <libtwl/ipc/ipcSync.h>
+#include <libtwl/ipc/ipcFifoSystem.h>
+#include <libtwl/sys/sysPower.h>
+#include <libtwl/sio/sioRtc.h>
+#include <libtwl/sio/sio.h>
+#include <libtwl/gfx/gfxStatus.h>
+#include <libtwl/mem/memSwap.h>
+#include <libtwl/i2c/i2cMcu.h>
+#include <libtwl/spi/spiPmic.h>
+#include "ExitMode.h"
+#include "Arm7State.h"
+#include "tusb.h"
+#include "usb_descriptors.h"
+#include "microphone.h"
+
+rtos_mutex_t gCardMutex;
+
+static rtos_thread_t sUsbThread;
+static u32 sUsbThreadStack[512];
+
+static rtos_event_t sVBlankEvent;
+static ExitMode sExitMode;
+static Arm7State sState;
+static volatile u8 sMcuIrqFlag = false;
+
+static void vblankIrq(u32 irqMask)
+{
+    rtos_signalEvent(&sVBlankEvent);
+}
+
+static void mcuIrq(u32 irq2Mask)
+{
+    sMcuIrqFlag = true;
+}
+
+static void checkMcuIrq(void)
+{
+    // mcu only exists in DSi mode
+    if (isDSiMode())
+    {
+        // check and ack the flag atomically
+        if (mem_swapByte(false, &sMcuIrqFlag))
+        {
+            // check the irq mask
+            u32 irqMask = mcu_getIrqMask();
+            if (irqMask & MCU_IRQ_RESET)
+            {
+                // power button was released
+                sExitMode = ExitMode::Reset;
+                sState = Arm7State::ExitRequested;
+            }
+            else if (irqMask & MCU_IRQ_POWER_OFF)
+            {
+                // power button was held long to trigger a power off
+                sExitMode = ExitMode::PowerOff;
+                sState = Arm7State::ExitRequested;
+            }
+        }
+    }
+}
+
+static void initializeVBlankIrq()
+{
+    rtos_createEvent(&sVBlankEvent);
+    rtos_setIrqFunc(RTOS_IRQ_VBLANK, vblankIrq);
+    rtos_enableIrqMask(RTOS_IRQ_VBLANK);
+    gfx_setVBlankIrqEnabled(true);
+}
+
+static void usbThreadMain(void* arg)
+{
+    while (true)
+    {
+        tud_task();
+    }
+}
+
+static void initializeArm7()
+{
+    rtos_initIrq();
+    rtos_startMainThread();
+    ipc_initFifoSystem();
+
+    // clear sound registers
+    dmaFillWords(0, (void*)0x04000400, 0x100);
+
+    pmic_setAmplifierEnable(true);
+    sys_setSoundPower(true);
+
+    readUserSettings();
+    pmic_setPowerLedBlink(PMIC_CONTROL_POWER_LED_BLINK_NONE);
+
+    sio_setGpioSiIrq(false);
+    sio_setGpioMode(RCNT0_L_MODE_GPIO);
+
+    rtc_init();
+
+    snd_setMasterVolume(0);
+    snd_setMasterEnable(false);
+
+    initializeVBlankIrq();
+
+    if (isDSiMode())
+    {
+        rtos_setIrq2Func(RTOS_IRQ2_MCU, mcuIrq);
+        rtos_enableIrq2Mask(RTOS_IRQ2_MCU);
+        mic_initialize();
+    }
+
+    pmic_setTopBacklightEnable(false);
+    pmic_setBottomBacklightEnable(false);
+
+    tusb_rhport_init_t dev_init =
+    {
+        .role = TUSB_ROLE_DEVICE,
+        .speed = TUSB_SPEED_AUTO
+    };
+    tusb_init(0, &dev_init);
+
+    rtos_createThread(&sUsbThread, 3, usbThreadMain, NULL, sUsbThreadStack, sizeof(sUsbThreadStack));
+    rtos_wakeupThread(&sUsbThread);
+
+    ipc_setArm7SyncBits(7);
+}
+
+static void updateArm7IdleState()
+{
+    checkMcuIrq();
+
+    if (sState == Arm7State::ExitRequested)
+    {
+        snd_setMasterVolume(0); // mute sound
+    }
+}
+
+static bool performExit(ExitMode exitMode)
+{
+    switch (exitMode)
+    {
+        case ExitMode::Reset:
+        {
+            mcu_setWarmBootFlag(true);
+            mcu_hardReset();
+            break;
+        }
+        case ExitMode::PowerOff:
+        {
+            pmic_shutdown();
+            break;
+        }
+    }
+
+    while (true); // wait infinitely for exit
+}
+
+static void updateArm7ExitRequestedState()
+{
+    performExit(sExitMode);
+}
+
+static void updateArm7()
+{
+    switch (sState)
+    {
+        case Arm7State::Idle:
+        {
+            updateArm7IdleState();
+            break;
+        }
+        case Arm7State::ExitRequested:
+        {
+            updateArm7ExitRequestedState();
+            break;
+        }
+    }
+}
+
+int main()
+{
+    sState = Arm7State::Idle;
+    initializeArm7();
+
+    while (true)
+    {
+        rtos_waitEvent(&sVBlankEvent, true, true);
+        updateArm7();
+    }
+
+    return 0;
+}

examples/usb-microphone/arm7/source/microphone.cpp

@@ -0,0 +1,282 @@
+#include "common.h"
+#include <libtwl/rtos/rtosIrq.h>
+#include <libtwl/spi/spiCodec.h>
+#include <libtwl/sound/twlMicrophone.h>
+#include <libtwl/sound/twlI2s.h>
+#include <libtwl/sys/swi.h>
+#include "tusb.h"
+#include "usb_descriptors.h"
+#include "microphone.h"
+
+#define AUDIO_BLOCK_SIZE_IN_BYTES   32
+#define NUMBER_OF_AUDIO_BUFFERS     128
+
+static s16 sAudioBuffer[NUMBER_OF_AUDIO_BUFFERS][16];
+static volatile int sReadBlock;
+static volatile int sWriteBlock;
+
+static bool sCaptureStarted = false;
+static int sOffset = 0;
+
+static bool sChannelMute[CFG_TUD_AUDIO_FUNC_1_N_CHANNELS_TX + 1]; // +1 for master channel 0
+static uint16_t sChannelVolume[CFG_TUD_AUDIO_FUNC_1_N_CHANNELS_TX + 1]; // +1 for master channel 0
+
+void mic_initialize()
+{
+    twlmic_stop();
+    REG_I2SCNT = I2SCNT_MIX_RATIO_DSP_0_NITRO_8 | I2SCNT_FREQUENCY_32728_HZ;
+    codec_setPage(CODEC_PAGE_0);
+    {
+        codec_writeRegister(CODEC_REG_PAGE0_DAC_NDAC_VAL, 0x87);
+        codec_writeRegister(CODEC_REG_PAGE0_ADC_NADC_VAL, 0x87);
+        codec_writeRegister(CODEC_REG_PAGE0_PLL_J, 21);
+    }
+    REG_I2SCNT |= I2SCNT_ENABLE;
+    codec_setPage(CODEC_PAGE_1);
+    {
+        codec_writeRegister(CODEC_REG_PAGE1_MICBIAS, 3);
+    }
+    bool adcOn, dacOn;
+    codec_setPage(CODEC_PAGE_0);
+    {
+        adcOn = codec_readRegister(CODEC_REG_PAGE0_ADC_DIGITAL_MIC) & 0x80;
+        dacOn = codec_readRegister(CODEC_REG_PAGE0_DAC_DATA_PATH_SETUP) & 0xC0;
+        codec_writeRegister(CODEC_REG_PAGE0_ADC_DIGITAL_MIC, 0x80);
+        if (!adcOn || !dacOn)
+        {
+            swi_waitByLoop(0x28E91F); // 20ms
+        }
+        codec_writeRegister(CODEC_REG_PAGE0_ADC_DIGITAL_VOLUME_CONTROL_FINE_ADJUST, 0);
+        codec_writeRegister(CODEC_REG_PAGE0_AGC_CONTROL_1, 0);
+    }
+    codec_setPage(CODEC_PAGE_1);
+    {
+        sChannelVolume[0] = 40; // dB
+        codec_writeRegister(CODEC_REG_PAGE1_MIC_PGA, sChannelVolume[0] * 2); // gain
+    }
+}
+
+static void micIrq(u32 irq2Mask)
+{
+    u32 data[8];
+    data[0] = REG_MIC_FIFO;
+    data[1] = REG_MIC_FIFO;
+    data[2] = REG_MIC_FIFO;
+    data[3] = REG_MIC_FIFO;
+    data[4] = REG_MIC_FIFO;
+    data[5] = REG_MIC_FIFO;
+    data[6] = REG_MIC_FIFO;
+    data[7] = REG_MIC_FIFO;
+    int writeBlock = sWriteBlock;
+    int nextWriteBlock = (writeBlock + 1) % NUMBER_OF_AUDIO_BUFFERS;
+    if (nextWriteBlock != sReadBlock)
+    {
+        memcpy(&sAudioBuffer[writeBlock][0], data, sizeof(data));
+        sWriteBlock = nextWriteBlock;
+    }
+}
+
+static void startMicrophoneCapture()
+{
+    sReadBlock = 0;
+    sWriteBlock = 0;
+    sOffset = 0;
+    twlmic_stop();
+    twlmic_configure(MICCNT_FORMAT_NORMAL, MICCNT_RATE_DIV_1, MICCNT_IRQ_HALF_OVERFLOW);
+    twlmic_clearFifo();
+    rtos_setIrq2Func(RTOS_IRQ2_MIC, micIrq);
+    rtos_ackIrq2Mask(RTOS_IRQ2_MIC);
+    rtos_enableIrq2Mask(RTOS_IRQ2_MIC);
+    twlmic_start();
+    sCaptureStarted = true;
+}
+
+static void stopMicrophoneCapture()
+{
+    rtos_disableIrq2Mask(RTOS_IRQ2_MIC);
+    twlmic_stop();
+    rtos_ackIrq2Mask(RTOS_IRQ2_MIC);
+    sCaptureStarted = false;
+}
+
+static bool handleMicInputTerminalGetRequest(u8 rhport, const tusb_control_request_t* p_request)
+{
+    u8 ctrlSel = TU_U16_HIGH(p_request->wValue);
+    switch (ctrlSel)
+    {
+        case AUDIO_TE_CTRL_CONNECTOR: // Get terminal connector
+        {
+            audio_desc_channel_cluster_t ret;
+            ret.bNrChannels = 1;
+            ret.bmChannelConfig = (audio_channel_config_t)0;
+            ret.iChannelNames = 0;
+            return tud_audio_buffer_and_schedule_control_xfer(rhport, p_request, (void*) &ret, sizeof(ret));
+        }
+    }
+
+    return false;
+}
+
+static bool handleFeatureUnitGetRequest(u8 rhport, const tusb_control_request_t* p_request)
+{
+    u8 channelNum = TU_U16_LOW(p_request->wValue);
+    u8 ctrlSel = TU_U16_HIGH(p_request->wValue);
+    switch (ctrlSel)
+    {
+        case AUDIO_FU_CTRL_MUTE: // Get Mute of channel
+        {
+            return tud_control_xfer(rhport, p_request, &sChannelMute[channelNum], 1);
+        }
+        case AUDIO_FU_CTRL_VOLUME:
+        {
+            switch (p_request->bRequest)
+            {
+                case AUDIO_CS_REQ_CUR: // Get Volume of channel
+                {
+                    return tud_control_xfer(rhport, p_request, &sChannelVolume[channelNum], sizeof(sChannelVolume[channelNum]));
+                }
+                case AUDIO_CS_REQ_RANGE: // Get Volume range of channel
+                {
+                    audio_control_range_2_n_t(1) ret;
+                    ret.wNumSubRanges = 1;
+                    ret.subrange[0].bMin = 0;  // 0 dB
+                    ret.subrange[0].bMax = 59; // +59 dB
+                    ret.subrange[0].bRes = 1;  // 1 dB steps
+                    return tud_audio_buffer_and_schedule_control_xfer(rhport, p_request, (void*) &ret, sizeof(ret));
+                }
+            }
+            break;
+        }
+    }
+
+    return false;
+}
+
+static bool handleFeatureUnitSetRequest(u8 rhport, const tusb_control_request_t* p_request, u8* pBuff)
+{
+    u8 channelNum = TU_U16_LOW(p_request->wValue);
+    u8 ctrlSel = TU_U16_HIGH(p_request->wValue);
+    switch (ctrlSel)
+    {
+        case AUDIO_FU_CTRL_MUTE: // Set Mute of channel
+        {
+            sChannelMute[channelNum] = ((audio_control_cur_1_t*)pBuff)->bCur;
+            return true;
+        }
+        case AUDIO_FU_CTRL_VOLUME: // Set Volume of channel
+        {
+            // Request uses format layout 2
+            sChannelVolume[channelNum] = (uint16_t) ((audio_control_cur_2_t*)pBuff)->bCur;
+            codec_setPage(CODEC_PAGE_1);
+            {
+                codec_writeRegister(CODEC_REG_PAGE1_MIC_PGA, sChannelVolume[channelNum] * 2); // gain
+            }
+            return true;
+        }
+    }
+
+    return false;
+}
+
+static bool handleClockGetRequest(u8 rhport, const tusb_control_request_t* p_request)
+{
+    u8 ctrlSel = TU_U16_HIGH(p_request->wValue);
+    switch (ctrlSel)
+    {
+        case AUDIO_CS_CTRL_SAM_FREQ:
+        {
+            switch (p_request->bRequest)
+            {
+                case AUDIO_CS_REQ_CUR: // Get Sample Freq.
+                {
+                    uint32_t sampFreq = CFG_TUD_AUDIO_FUNC_1_SAMPLE_RATE;
+                    return tud_control_xfer(rhport, p_request, &sampFreq, sizeof(sampFreq));
+                }
+                case AUDIO_CS_REQ_RANGE: // Get Sample Freq. range
+                {
+                    audio_control_range_4_n_t(1) sampleFreqRng;
+                    sampleFreqRng.wNumSubRanges = 1;
+                    sampleFreqRng.subrange[0].bMin = CFG_TUD_AUDIO_FUNC_1_SAMPLE_RATE;
+                    sampleFreqRng.subrange[0].bMax = CFG_TUD_AUDIO_FUNC_1_SAMPLE_RATE;
+                    sampleFreqRng.subrange[0].bRes = 0;
+                    return tud_control_xfer(rhport, p_request, &sampleFreqRng, sizeof(sampleFreqRng));
+                }
+            }
+            break;
+        }
+        case AUDIO_CS_CTRL_CLK_VALID: // Get Sample Freq. valid
+        {
+            uint8_t clkValid = 1;
+            return tud_control_xfer(rhport, p_request, &clkValid, sizeof(clkValid));
+        }
+    }
+
+    return false;
+}
+
+// Invoked when audio class specific get request received for an entity
+bool tud_audio_get_req_entity_cb(u8 rhport, const tusb_control_request_t* p_request)
+{
+    u8 entityId = TU_U16_HIGH(p_request->wIndex);
+    switch (entityId)
+    {
+        case UAC2_ENTITY_MIC_INPUT_TERMINAL:
+        {
+            return handleMicInputTerminalGetRequest(rhport, p_request);
+        }
+        case UAC2_ENTITY_FEATURE_UNIT:
+        {
+            return handleFeatureUnitGetRequest(rhport, p_request);
+        }
+        case UAC2_ENTITY_CLOCK:
+        {
+            return handleClockGetRequest(rhport, p_request);
+        }
+    }
+
+    return false;
+}
+
+// Invoked when audio class specific set request received for an entity
+bool tud_audio_set_req_entity_cb(u8 rhport, const tusb_control_request_t* p_request, u8* pBuff)
+{
+    u8 entityId = TU_U16_HIGH(p_request->wIndex);
+    switch (entityId)
+    {
+        case UAC2_ENTITY_FEATURE_UNIT:
+        {
+            return handleFeatureUnitSetRequest(rhport, p_request, pBuff);
+        }
+    }
+
+    return false;
+}
+
+bool tud_audio_tx_done_pre_load_cb(u8 rhport, u8 itf, u8 ep_in, u8 cur_alt_setting)
+{
+    if (!sCaptureStarted)
+    {
+        startMicrophoneCapture();
+    }
+
+    while (sReadBlock != sWriteBlock)
+    {
+        int bytesWritten = tud_audio_write(((u8*)&sAudioBuffer[sReadBlock][0]) + sOffset, AUDIO_BLOCK_SIZE_IN_BYTES - sOffset);
+        int offset = AUDIO_BLOCK_SIZE_IN_BYTES - bytesWritten;
+        sOffset = offset % AUDIO_BLOCK_SIZE_IN_BYTES;
+        if (offset > 0)
+        {
+            // Could not write entire block
+            break;
+        }
+        sReadBlock = (sReadBlock + 1) % NUMBER_OF_AUDIO_BUFFERS;
+    }
+
+  return true;
+}
+
+bool tud_audio_set_itf_close_EP_cb(u8 rhport, const tusb_control_request_t* p_request)
+{
+    stopMicrophoneCapture();
+    return true;
+}

examples/usb-microphone/arm7/source/microphone.h

@@ -0,0 +1,3 @@
+#pragma once
+
+void mic_initialize();

examples/usb-microphone/arm7/source/tusb_config.h

@@ -0,0 +1,97 @@
+#pragma once
+#include "usb_descriptors.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+//--------------------------------------------------------------------+
+// Board Specific Configuration
+//--------------------------------------------------------------------+
+
+// RHPort number used for device can be defined by board.mk, default to port 0
+#ifndef BOARD_TUD_RHPORT
+#define BOARD_TUD_RHPORT      0
+#endif
+
+// RHPort max operational speed can defined by board.mk
+#ifndef BOARD_TUD_MAX_SPEED
+#define BOARD_TUD_MAX_SPEED   OPT_MODE_DEFAULT_SPEED
+#endif
+
+//--------------------------------------------------------------------
+// COMMON CONFIGURATION
+//--------------------------------------------------------------------
+
+// defined by compiler flags for flexibility
+#ifndef CFG_TUSB_MCU
+#define CFG_TUSB_MCU          OPT_MCU_DSPICO
+#endif
+
+#define TUP_DCD_ENDPOINT_MAX    16
+
+#ifndef CFG_TUSB_OS
+#define CFG_TUSB_OS           OPT_OS_CUSTOM
+#endif
+
+#ifndef CFG_TUSB_DEBUG
+#define CFG_TUSB_DEBUG        0
+#endif
+
+// Enable Device stack
+#define CFG_TUD_ENABLED       1
+
+// Default is max speed that hardware controller could support with on-chip PHY
+#define CFG_TUD_MAX_SPEED     BOARD_TUD_MAX_SPEED
+
+/* USB DMA on some MCUs can only access a specific SRAM region with restriction on alignment.
+ * Tinyusb use follows macros to declare transferring memory so that they can be put
+ * into those specific section.
+ * e.g
+ * - CFG_TUSB_MEM SECTION : __attribute__ (( section(".usb_ram") ))
+ * - CFG_TUSB_MEM_ALIGN   : __attribute__ ((aligned(4)))
+ */
+#ifndef CFG_TUSB_MEM_SECTION
+#define CFG_TUSB_MEM_SECTION
+#endif
+
+#ifndef CFG_TUSB_MEM_ALIGN
+#define CFG_TUSB_MEM_ALIGN          __attribute__ ((aligned(4)))
+#endif
+
+//--------------------------------------------------------------------
+// DEVICE CONFIGURATION
+//--------------------------------------------------------------------
+
+#ifndef CFG_TUD_ENDPOINT0_SIZE
+#define CFG_TUD_ENDPOINT0_SIZE    64
+#endif
+
+//------------- CLASS -------------//
+#define CFG_TUD_CDC               0
+#define CFG_TUD_MSC               0
+#define CFG_TUD_HID               0
+#define CFG_TUD_MIDI              0
+#define CFG_TUD_AUDIO             1
+#define CFG_TUD_VENDOR            0
+
+//--------------------------------------------------------------------
+// AUDIO CLASS DRIVER CONFIGURATION
+//--------------------------------------------------------------------
+
+#define CFG_TUD_AUDIO_FUNC_1_SAMPLE_RATE                              32728
+#define CFG_TUD_AUDIO_FUNC_1_DESC_LEN                                 TUD_AUDIO_MIC_ONE_CH_DESC_LEN
+#define CFG_TUD_AUDIO_FUNC_1_N_AS_INT                                 1                                       // Number of Standard AS Interface Descriptors (4.9.1) defined per audio function - this is required to be able to remember the current alternate settings of these interfaces - We restrict us here to have a constant number for all audio functions (which means this has to be the maximum number of AS interfaces an audio function has and a second audio function with less AS interfaces just wastes a few bytes)
+#define CFG_TUD_AUDIO_FUNC_1_CTRL_BUF_SZ                              64                                      // Size of control request buffer
+
+#define CFG_TUD_AUDIO_ENABLE_EP_IN                                    1
+#define CFG_TUD_AUDIO_FUNC_1_N_BYTES_PER_SAMPLE_TX                    2                                       // Driver gets this info from the descriptors - we define it here to use it to setup the descriptors and to do calculations with it below
+#define CFG_TUD_AUDIO_FUNC_1_N_CHANNELS_TX                            1                                       // Driver gets this info from the descriptors - we define it here to use it to setup the descriptors and to do calculations with it below - be aware: for different number of channels you need another descriptor!
+#define CFG_TUD_AUDIO_EP_SZ_IN                                        TUD_AUDIO_EP_SIZE(CFG_TUD_AUDIO_FUNC_1_SAMPLE_RATE, CFG_TUD_AUDIO_FUNC_1_N_BYTES_PER_SAMPLE_TX, CFG_TUD_AUDIO_FUNC_1_N_CHANNELS_TX)
+#define CFG_TUD_AUDIO_FUNC_1_EP_IN_SZ_MAX                             CFG_TUD_AUDIO_EP_SZ_IN
+#define CFG_TUD_AUDIO_FUNC_1_EP_IN_SW_BUF_SZ                          256 //(TUD_OPT_HIGH_SPEED ? 8 : 1) * CFG_TUD_AUDIO_EP_SZ_IN // Example write FIFO every 1ms, so it should be 8 times larger for HS device
+
+
+#ifdef __cplusplus
+}
+#endif

examples/usb-microphone/arm7/source/usb_descriptors.cpp

@@ -0,0 +1,94 @@
+#include "common.h"
+#include "UsbStringDescriptor.h"
+#include "tusb.h"
+#include "usb_descriptors.h"
+
+/* A combination of interfaces must have a unique product id, since PC will save device driver after the first plug.
+ * Same VID/PID with different interface e.g MSC (first), then CDC (later) will possibly cause system error on PC.
+ *
+ * Auto ProductID layout's Bitmap:
+ *   [MSB]     AUDIO | MIDI | HID | MSC | CDC          [LSB]
+ */
+#define _PID_MAP(itf, n)  ( (CFG_TUD_##itf) << (n) )
+#define USB_PID           (0x5000 | _PID_MAP(CDC, 0) | _PID_MAP(MSC, 1) | _PID_MAP(HID, 2) | \
+    _PID_MAP(MIDI, 3) | _PID_MAP(AUDIO, 4) | _PID_MAP(VENDOR, 5) )
+
+const u8* tud_descriptor_device_cb(void)
+{
+    static const tusb_desc_device_t deviceDescriptor =
+    {
+        .bLength            = sizeof(tusb_desc_device_t),
+        .bDescriptorType    = TUSB_DESC_DEVICE,
+        .bcdUSB             = 0x0200,
+
+        // Use Interface Association Descriptor (IAD) for Audio
+        // As required by USB Specs IAD's subclass must be common class (2) and protocol must be IAD (1)
+        .bDeviceClass       = TUSB_CLASS_MISC,
+        .bDeviceSubClass    = MISC_SUBCLASS_COMMON,
+        .bDeviceProtocol    = MISC_PROTOCOL_IAD,
+        .bMaxPacketSize0    = CFG_TUD_ENDPOINT0_SIZE,
+
+        .idVendor           = 0xCafe,
+        .idProduct          = USB_PID,
+        .bcdDevice          = 0x0100,
+
+        .iManufacturer      = STRID_MANUFACTURER,
+        .iProduct           = STRID_PRODUCT,
+        .iSerialNumber      = STRID_SERIAL,
+
+        .bNumConfigurations = 0x01
+    };
+
+    return (const u8*)&deviceDescriptor;
+}
+
+#define CONFIG_TOTAL_LEN    (TUD_CONFIG_DESC_LEN + TUD_AUDIO_MIC_ONE_CH_DESC_LEN)
+
+const u8* tud_descriptor_configuration_cb(u8 index)
+{
+    (void)index;
+
+    static const u8 configurationDescriptor[] =
+    {
+        // Config number, interface count, string index, total length, attribute, power in mA
+        TUD_CONFIG_DESCRIPTOR(1, ITF_NUM_TOTAL, 0, CONFIG_TOTAL_LEN, 0x00, 100),
+
+        TUD_AUDIO_MIC_ONE_CH_DESCRIPTOR(0, STRID_AUDIO_INTERFACE,
+            CFG_TUD_AUDIO_FUNC_1_N_BYTES_PER_SAMPLE_TX, CFG_TUD_AUDIO_FUNC_1_N_BYTES_PER_SAMPLE_TX * 8,
+            EPNUM_AUDIO_IN, CFG_TUD_AUDIO_EP_SZ_IN)
+    };
+
+    return configurationDescriptor;
+}
+
+const u16* tud_descriptor_string_cb(u8 index, u16 langid)
+{
+    switch (index)
+    {
+        case STRID_LANGID:
+        {
+            static const UsbStringDescriptor<2> descriptor(0x0409);
+            return (const u16*)&descriptor;
+        }
+        case STRID_MANUFACTURER:
+        {
+            return USB_STRING_DESCRIPTOR(u"LNH");
+        }
+        case STRID_PRODUCT:
+        {
+            return USB_STRING_DESCRIPTOR(u"DSpico Microphone Example");
+        }
+        case STRID_SERIAL:
+        {
+            return USB_STRING_DESCRIPTOR(u"123456789");
+        }
+        case STRID_AUDIO_INTERFACE:
+        {
+            return USB_STRING_DESCRIPTOR(u"DSpico Microphone");
+        }
+        default:
+        {
+            return nullptr;
+        }
+    }
+}

examples/usb-microphone/arm7/source/usb_descriptors.h

@@ -0,0 +1,24 @@
+#pragma once
+
+enum
+{
+    STRID_LANGID = 0,
+    STRID_MANUFACTURER,
+    STRID_PRODUCT,
+    STRID_SERIAL,
+    STRID_AUDIO_INTERFACE
+};
+
+enum
+{
+    ITF_NUM_AUDIO_CONTROL = 0,
+    ITF_NUM_AUDIO_STREAMING,
+    ITF_NUM_TOTAL
+};
+
+#define UAC2_ENTITY_MIC_INPUT_TERMINAL  0x01
+#define UAC2_ENTITY_FEATURE_UNIT        0x02
+#define UAC2_ENTITY_MIC_OUTPUT_TERMINAL 0x03
+#define UAC2_ENTITY_CLOCK               0x04
+
+#define EPNUM_AUDIO_IN      0x81

examples/usb-microphone/arm9/Makefile

@@ -0,0 +1,152 @@
+#---------------------------------------------------------------------------------
+.SUFFIXES:
+#---------------------------------------------------------------------------------
+ifeq ($(strip $(DEVKITARM)),)
+$(error "Please set DEVKITARM in your environment. export DEVKITARM=<path to>devkitARM")
+endif
+
+include $(DEVKITARM)/ds_rules
+
+#---------------------------------------------------------------------------------
+# BUILD is the directory where object files & intermediate files will be placed
+# SOURCES is a list of directories containing source code
+# INCLUDES is a list of directories containing extra header files
+# DATA is a list of directories containing binary files
+# all directories are relative to this makefile
+#---------------------------------------------------------------------------------
+BUILD		:=	build
+SOURCES		:=	source \
+				source/core
+INCLUDES	:=	include source ../common
+DATA		:=  data
+GRAPHICS 	:=  gfx
+
+
+#---------------------------------------------------------------------------------
+# options for code generation
+#---------------------------------------------------------------------------------
+ARCH	:=	-marm -mthumb-interwork -DLIBTWL_ARM9 -DARM9
+
+CFLAGS	:=	-g -Wall -O2\
+ 			-march=armv5te -mtune=arm946e-s -fomit-frame-pointer\
+			-ffunction-sections -fdata-sections\
+			-ffast-math \
+			-fno-devirtualize-speculatively \
+			-Werror=return-type \
+			$(ARCH)
+
+CFLAGS	+=	$(INCLUDE)
+CXXFLAGS	:=	$(CFLAGS) -std=gnu++23 -Wno-volatile -fno-rtti -fno-exceptions -fno-threadsafe-statics\
+				-Wsuggest-override -Werror=suggest-override
+
+CFLAGS += -Werror=implicit-function-declaration
+
+ASFLAGS	:=	-g $(ARCH) $(INCLUDE) -march=armv5te -mtune=arm946e-s
+
+LDFLAGS	=	-specs=ds_arm9.specs -g $(ARCH) -Wl,-Map,$(notdir $*.map),--gc-sections,--use-blx -ffunction-sections -fdata-sections
+
+#---------------------------------------------------------------------------------
+# any extra libraries we wish to link with the project
+#---------------------------------------------------------------------------------
+LIBS	:=	-ltwl9 -lnds9
+ 
+#---------------------------------------------------------------------------------
+# list of directories containing libraries, this must be the top level containing
+# include and lib
+#---------------------------------------------------------------------------------
+LIBDIRS	:=	$(LIBNDS) $(CURDIR)/../../../libs/libtwl/libtwl9 $(CURDIR)/../../../libs/libtwl/common
+ 
+#---------------------------------------------------------------------------------
+# no real need to edit anything past this point unless you need to add additional
+# rules for different file extensions
+#---------------------------------------------------------------------------------
+ifneq ($(BUILD),$(notdir $(CURDIR)))
+#---------------------------------------------------------------------------------
+ 
+export ARM9ELF	:=	$(CURDIR)/$(TARGET).elf
+export DEPSDIR := $(CURDIR)/$(BUILD)
+
+export VPATH	:=	$(foreach dir,$(SOURCES),$(CURDIR)/$(dir)) \
+					$(foreach dir,$(DATA),$(CURDIR)/$(dir)) \
+					$(foreach dir,$(GRAPHICS),$(CURDIR)/$(dir))
+ 
+CFILES		:=	$(foreach dir,$(SOURCES),$(notdir $(wildcard $(dir)/*.c)))
+CPPFILES	:=	$(foreach dir,$(SOURCES),$(notdir $(wildcard $(dir)/*.cpp)))
+SFILES		:=	$(foreach dir,$(SOURCES),$(notdir $(wildcard $(dir)/*.s)))
+BINFILES	:=	$(foreach dir,$(DATA),$(notdir $(wildcard $(dir)/*.*)))
+PNGFILES 	:=  $(foreach dir,$(GRAPHICS),$(notdir $(wildcard $(dir)/*.png)))
+ 
+#---------------------------------------------------------------------------------
+# use CXX for linking C++ projects, CC for standard C
+#---------------------------------------------------------------------------------
+ifeq ($(strip $(CPPFILES)),)
+#---------------------------------------------------------------------------------
+	export LD	:=	$(CC)
+#---------------------------------------------------------------------------------
+else
+#---------------------------------------------------------------------------------
+	export LD	:=	$(CXX)
+#---------------------------------------------------------------------------------
+endif
+#---------------------------------------------------------------------------------
+
+export OFILES	:=	$(addsuffix .o,$(BINFILES)) \
+					$(PNGFILES:.png=.o)\
+					$(CPPFILES:.cpp=.o) $(CFILES:.c=.o) $(SFILES:.s=.o)
+ 
+export INCLUDE	:=	$(foreach dir,$(INCLUDES),-I$(CURDIR)/$(dir)) \
+			$(foreach dir,$(LIBDIRS),-I$(dir)/include) \
+			-I$(CURDIR)/$(BUILD)
+ 
+export LIBPATHS	:=	$(foreach dir,$(LIBDIRS),-L$(dir)/lib)
+ 
+.PHONY: $(BUILD) clean
+ 
+#---------------------------------------------------------------------------------
+$(BUILD):
+	@[ -d $@ ] || mkdir -p $@
+	@$(MAKE) --no-print-directory -C $(BUILD) -f $(CURDIR)/Makefile
+ 
+#---------------------------------------------------------------------------------
+clean:
+	@echo clean ...
+	@rm -fr $(BUILD) *.elf *.nds* *.bin 
+ 
+ 
+#---------------------------------------------------------------------------------
+else
+ 
+#---------------------------------------------------------------------------------
+# main targets
+#---------------------------------------------------------------------------------
+$(ARM9ELF)	:	$(OFILES)
+	@echo linking $(notdir $@)
+	@$(LD)  $(LDFLAGS) $(OFILES) $(LIBPATHS) $(LIBS) -o $@
+
+#---------------------------------------------------------------------------------
+# you need a rule like this for each extension you use as binary data 
+#---------------------------------------------------------------------------------
+%.bin.o	:	%.bin
+#---------------------------------------------------------------------------------
+	@echo $(notdir $<)
+	@$(bin2o)
+
+%.nft2.o	:	%.nft2
+	@echo $(notdir $<)
+	@$(bin2o)
+
+#---------------------------------------------------------------------------------
+# This rule creates assembly source files using grit
+# grit takes an image file and a .grit describing how the file is to be processed
+# add additional rules like this for each image extension
+# you use in the graphics folders
+#---------------------------------------------------------------------------------
+%.s %.h: %.png %.grit
+#---------------------------------------------------------------------------------
+	grit $< -fts -o$*
+
+-include $(DEPSDIR)/*.d
+ 
+#---------------------------------------------------------------------------------------
+endif
+#---------------------------------------------------------------------------------------

examples/usb-microphone/arm9/source/main.cpp

@@ -0,0 +1,51 @@
+#include <nds/ndstypes.h>
+#include <libtwl/gfx/gfxStatus.h>
+#include <libtwl/mem/memExtern.h>
+#include <libtwl/rtos/rtosIrq.h>
+#include <libtwl/rtos/rtosThread.h>
+#include <libtwl/rtos/rtosEvent.h>
+#include <libtwl/ipc/ipcSync.h>
+#include <libtwl/ipc/ipcFifoSystem.h>
+
+static rtos_event_t sVblankEvent;
+
+static void vblankIrq(u32 irqMask)
+{
+    rtos_signalEvent(&sVblankEvent);
+}
+
+int main(int argc, char* argv[])
+{
+    *(vu32*)0x04000000 = 0x10000;
+    *(vu16*)0x05000000 = 31 << 5;
+    *(vu16*)0x0400006C = 0;
+
+    mem_setDsCartridgeCpu(EXMEMCNT_SLOT1_CPU_ARM7);
+
+    rtos_initIrq();
+    rtos_startMainThread();
+    ipc_initFifoSystem();
+
+    rtos_createEvent(&sVblankEvent);
+
+    while (ipc_getArm7SyncBits() != 7);
+
+    ipc_setArm9SyncBits(6);
+
+    rtos_setIrqFunc(RTOS_IRQ_VBLANK, vblankIrq);
+    rtos_enableIrqMask(RTOS_IRQ_VBLANK);
+    gfx_setVBlankIrqEnabled(true);
+
+    *(vu16*)0x05000000 = 0;
+
+    *(vu32*)0x04001000 = 0x10000;
+    *(vu16*)0x05000400 = 0;
+    *(vu16*)0x0400106C = 0;
+
+    while (true)
+    {
+        rtos_waitEvent(&sVblankEvent, true, true);
+    }
+
+    return 0;
+}