USB Audio Class 1.0 device-mode smoke test for EK-RA8D2 (USB-FS, 48 kHz / 16-bit / stereo iso-IN sine generator). More...

#include <stdint.h>
#include "ra8_attributes.h"
#include "ra8_board_ek_ra8d2.h"
#include "ra8_boot_entry.h"
#include "ra8_cgc.h"
#include "ra8_err.h"
#include "ra8_isr.h"
#include "ra8_nsc_comms.h"
#include "ra8_time.h"
#include "ra8_usb.h"
#include "ra8_usb_paud.h"

Include dependency graph for main.c:

Enumerations
enum	usb_audio_config_t : uint32_t { k_usb_audio_baud = 115200U , k_usb_audio_log_period = 1000U , k_usb_audio_idle_step_ms = 1U }
	Numeric configuration constants for the demo. More...
enum	usb_audio_format_t : uint32_t { k_usb_audio_sample_rate_hz = 48000U , k_usb_audio_channels = 2U , k_usb_audio_bytes_per_samp = 2U , k_usb_audio_lut_samples = 48U , k_usb_audio_lut_bytes = (uint32_t)(48U * 2U * 2U) }
	Audio format constants used to seed the format shadow. More...
enum	usb_audio_volume_t : int16_t { k_usb_audio_volume_0_db = 0 }
	Q8.8-format volume constant (USB Audio 1.0 sec 5.2.2.4.3.2). More...

Functions
static void	internal_usb_audio_panic_halt (void)
	Park the CPU forever in WFI on fatal init failure.
static void	internal_usb_audio_log (const char *s)
	Send a NUL-terminated ASCII line over SCI8 (best-effort).
static void	internal_usb_audio_u32_to_ascii (uint32_t value, char *buf, uint32_t cap)
	Convert a uint32_t to ASCII decimal in caller-supplied buffer.
static void	internal_usb_audio_clocks_or_halt (uint32_t *cpuclk0_hz)
	Bring up clocks, time, GPIO.
static void	internal_usb_audio_usb_or_halt (void)
	Bring up USB-FS pin mux + UAC1 class layer + format/volume shadows.
static void	internal_usb_audio_setup_or_halt (void)
	Bring up CGC + SysTick + GPIO + SCI8 + USB-FS + UAC1.
static ra8_err_t	internal_usb_audio_send_one_frame (void)
	Push one iso frame (1 ms = 48 stereo samples) on PIPE1.
static void	internal_usb_audio_log_frames (uint32_t frames)
	Emit one log line announcing the running frame count.
void	main (void)
	Application entry.

Variables
static const uint8_t	s_usb_audio_sine_lut [k_usb_audio_lut_bytes]
	1 kHz sine LUT, 48 stereo 16-bit samples per cycle.

Detailed Description

USB Audio Class 1.0 device-mode smoke test for EK-RA8D2 (USB-FS, 48 kHz / 16-bit / stereo iso-IN sine generator).

Tag: [Ring 6 / APP] {World: S}

Brings the chip up via ra8_cgc_init(), routes the four USB-FS pins to the EK-RA8D2 v1 USB-FS receptacle (J11), brings the device-mode UAC1 stack up via the NSC USB veneers + the ra8_usb_paud class layer, and feeds a precomputed 1 kHz sine wave (48-sample LUT – exactly one cycle at 48 kHz) into the iso-IN endpoint every USB-FS 1 ms frame so the host enumerates the gadget as a UAC1 microphone / headset and renders the test tone.

USB Audio Class 1.0 sec 2.2.5 "Format Type Descriptor" (Type-I PCM 16-bit, 2 channels, 48 kHz) and sec 5.2.3.2.3.1 "Sampling Frequency Control" frame the descriptor + class-request behaviour the driver synthesises around the LUT below.

Pinout (USB-FS, EK-RA8D2 v1)

Net	Pin	PFS PSEL	Notes
USB_FS_VBUS	P4_07	k_ra8_psel_usb_fs (0x13)	VBUS sense (input).
USB_FS_VBUSEN	P5_00	k_ra8_psel_usb_fs (0x13)	VBUS-enable drive (output).
USB_FS_DP	P8_14	k_ra8_psel_usb_fs (0x13)	D+ data line (analog buffer).
USB_FS_DM	P8_15	k_ra8_psel_usb_fs (0x13)	D- data line (analog buffer).

Pin assignments are copied verbatim from examples/usb_cdc_echo because the EK-RA8D2 v1 board only routes USB-FS to one pad set.

Sequence

ra8_cgc_init() – standard FSP-quickstart clock tree.
ra8_time_init(cpuclk0_hz) for ra8_delay_ms.
ra8_pfs_route_peripheral for the four USB-FS pins.
ra8_gpio_output_init(k_ra8_pin_led1, low) for the heartbeat.
ra8_board_uart_console_init (SCI8, PD_02 / PD_03) at 115200 8N1 for log output.
ra8_nsc_usb_init(k_ra8_usb_speed_fs) – secure veneer to ra8_usb_device_init.
ra8_usb_paud_init(k_ra8_usb_speed_fs) – iso-IN PIPE1 / iso-OUT PIPE2 configured at the FS default 192-byte max-packet (48 kHz stereo 16-bit per USB Audio 1.0 sec 3.7.1).
ra8_usb_paud_set_format – explicit 48 kHz / 2 ch / 16-bit.
ra8_usb_paud_set_volume(0) – 0 dB feature-unit volume (USB Audio 1.0 sec 5.2.2.4.3.2 "Volume Control" Q8.8 = 0).

ra8_nsc_usb_attach(k_ra8_usb_speed_fs, true) – raise D+ pull-up so the host begins enumeration.

Loop: feed 48 samples (one full cycle of the 1 kHz sine LUT) to ra8_usb_paud_send_frame per iteration, log every 1000 frames over SCI8, and toggle LED1 once per log line.

Architectural ring: [Ring 6 / APP] {World: S} – application-layer code that runs in the Secure world.

Author: Brighton Sikarskie

Date: 2026-04-29

Copyright: Copyright (c) 2026 Brighton Sikarskie SPDX-License-Identifier: MIT

Since: 0.1.0

Definition in file main.c.

Enumeration Type Documentation

◆ usb_audio_config_t

enum usb_audio_config_t : uint32_t

Numeric configuration constants for the demo.

Every literal used by the bring-up path lives here so the magic- number lint never sees a bare integer. The BSP console uses the on-board J-Link OB CDC bridge pins (PD_02 / PD_03) for log output.

Enumerator
k_usb_audio_baud	J-Link OB CDC log baud.
k_usb_audio_log_period	Frames per SCI8 log line.
k_usb_audio_idle_step_ms	USB-FS frame period.

Definition at line 90 of file main.c.

◆ usb_audio_format_t

enum usb_audio_format_t : uint32_t

Audio format constants used to seed the format shadow.

USB Audio 1.0 sec 2.2.5 "Format Type Descriptor" – Type-I PCM, 16-bit sub-frame, 2 channels, 48 kHz. The LUT below stores 48 stereo samples (one full cycle of a 1 kHz tone), which is exactly the FS iso payload of one microframe.

Enumerator
k_usb_audio_sample_rate_hz	Sample rate (Hz).
k_usb_audio_channels	Stereo.
k_usb_audio_bytes_per_samp	16-bit.
k_usb_audio_lut_samples	48 stereo samples per frame.
k_usb_audio_lut_bytes	48 samples * 2 ch * 2 bytes = 192 B.

Definition at line 106 of file main.c.

◆ usb_audio_volume_t

enum usb_audio_volume_t : int16_t

Q8.8-format volume constant (USB Audio 1.0 sec 5.2.2.4.3.2).

Enumerator
k_usb_audio_volume_0_db	0 dB attenuation, full scale.

Definition at line 118 of file main.c.

Function Documentation

◆ internal_usb_audio_clocks_or_halt()

void internal_usb_audio_clocks_or_halt ( uint32_t * cpuclk0_hz )

static

Bring up clocks, time, GPIO.

Panic-halts on any failure.

Initializes the CGC, reads CPUCLK0, starts the timebase, and claims LED1 in the dependency order required by the board support package.

Parameters

[out] cpuclk0_hz Receives CPUCLK0 rate.

Precondition: cpuclk0_hz non-null.; Reset initialization has completed with interrupts still controlled.

Postcondition: CGC + SysTick + LED1 GPIO are usable.; *cpuclk0_hz contains the rate used to configure the timebase.

Note: Any driver error is fail-stop and leaves the CPU parked in WFI.

Since: 0.1.0

Definition at line 307 of file main.c.

References internal_usb_audio_panic_halt(), k_ra8_board_led1, k_ra8_clock_id_cpuclk0, k_ra8_ok, ra8_board_led_init(), ra8_cgc_get_clock_hz(), ra8_cgc_init(), RA8_INTERNAL, and ra8_time_init().

Referenced by internal_usb_audio_setup_or_halt().

◆ internal_usb_audio_log()

void internal_usb_audio_log ( const char * s )

static

Send a NUL-terminated ASCII line over SCI8 (best-effort).

Measures the string locally and forwards exactly its payload bytes to the BSP console without a terminator or dynamic allocation.

Parameters

[in] s ASCII string (NUL-terminated). May be nullptr.

Precondition: ra8_board_uart_console_init() succeeded for the BSP console.; If non-NULL, s points to a readable NUL-terminated byte sequence.

Postcondition: Bytes have been polled out of TXD8 (or silently discarded on backpressure – this is logging only).; A NULL argument performs no console write.

Note: Console errors are intentionally non-fatal for diagnostic messages.

Since: 0.1.0

Definition at line 227 of file main.c.

References ra8_board_uart_console_write(), and RA8_INTERNAL.

Referenced by internal_usb_audio_log_frames(), and main().

◆ internal_usb_audio_log_frames()

void internal_usb_audio_log_frames ( uint32_t frames )

static

Emit one log line announcing the running frame count.

Formats the counter in a bounded stack buffer, emits three string fragments, and toggles the activity LED once.

Parameters

[in] frames Frame counter snapshot.

Precondition: SCI8 is initialized.; LED1 was initialized by the clock/setup stage.

Postcondition: One ASCII line written to SCI8 and LED1 toggled once.; The caller's frame counter is not modified.

Note: Console and LED errors are diagnostic-only and intentionally ignored.

Since: 0.1.0

< Decimal buffer for the frame counter.

Definition at line 440 of file main.c.

References internal_usb_audio_log(), internal_usb_audio_u32_to_ascii(), k_ra8_board_led1, ra8_board_led_toggle(), and RA8_INTERNAL.

Referenced by main().

◆ internal_usb_audio_panic_halt()

void internal_usb_audio_panic_halt ( void )

static

Park the CPU forever in WFI on fatal init failure.

Re-enters WFI indefinitely so the failing boot context remains available to a debugger without executing additional peripheral accesses.

Precondition: Called only after a fatal error in boot.; No safe continuation path remains for the current initialization.

Postcondition: CPU is parked; only a debugger or external reset wakes it.; USB and console state remain unchanged after entry.

Note: Logging is avoided because the console itself may have failed.

Since: 0.1.0

Definition at line 202 of file main.c.

References RA8_INTERNAL.

Referenced by internal_usb_audio_clocks_or_halt(), internal_usb_audio_setup_or_halt(), internal_usb_audio_usb_or_halt(), and main().

◆ internal_usb_audio_send_one_frame()

ra8_err_t internal_usb_audio_send_one_frame ( void )

staticnodiscard

Push one iso frame (1 ms = 48 stereo samples) on PIPE1.

Submits the immutable interleaved stereo LUT as one bounded UAC1 isochronous frame and returns the class driver's exact status.

Returns: Error code from ra8_usb_paud_send_frame.

Return values

k_ra8_ok	Bytes queued onto iso-IN.
k_ra8_err_invalid_state	Driver not initialized.
k_ra8_err_invalid_arg	LUT byte count out of range.

Precondition: ra8_usb_paud_init succeeded.; The host-selected audio format matches the fixed LUT geometry.

Postcondition: 192 bytes of LUT have been queued onto PIPE1.; On error the LUT and caller-owned USB state are not modified here.

Note: Retry policy belongs to the outer streaming loop.

Since: 0.1.0

Definition at line 418 of file main.c.

References k_usb_audio_lut_bytes, RA8_INTERNAL, ra8_usb_paud_send_frame(), and s_usb_audio_sine_lut.

Referenced by main().

◆ internal_usb_audio_setup_or_halt()

void internal_usb_audio_setup_or_halt ( void )

static

Bring up CGC + SysTick + GPIO + SCI8 + USB-FS + UAC1.

Panic-halts on any failure.

Mirrors usb_cdc_echo setup but swaps CDC for the UAC1 audio class. Split into clocks, console, and USB stages so each helper stays inside the NASA-rule-4 line budget.

Precondition: Reset_Handler has initialized data and BSS.; The application is still in single-threaded boot context.

Postcondition: Clocks, LED1, console, and USB audio are initialized on success.; Any setup error parks the CPU before the streaming loop starts.

Note: The local clock-rate value is passed only to the timebase setup path.

Since: 0.1.0

Definition at line 386 of file main.c.

References internal_usb_audio_clocks_or_halt(), internal_usb_audio_panic_halt(), internal_usb_audio_usb_or_halt(), k_ra8_ok, k_usb_audio_baud, ra8_board_uart_console_init(), and RA8_INTERNAL.

Referenced by main().

◆ internal_usb_audio_u32_to_ascii()

void internal_usb_audio_u32_to_ascii	(	uint32_t	value,
		char *	buf,
		uint32_t	cap )

static

Convert a uint32_t to ASCII decimal in caller-supplied buffer.

Builds digits in reverse order in a fixed local array and copies as many as fit, always terminating a nonzero-capacity destination.

Parameters

[in]	value	Value to format.
[out]	buf	Destination buffer (>= 11 bytes incl. NUL).
[in]	cap	Capacity of buf in bytes.

Precondition: buf != nullptr.; cap >= 11.

Postcondition: buf holds a NUL-terminated decimal representation of value.; No bytes at or beyond buf[cap] are accessed.

Note: Invalid zero-capacity input returns without writing; normal callers satisfy the documented eleven-byte capacity contract.

Since: 0.1.0

< Dec radix.

< Maximum digits.

Definition at line 259 of file main.c.

References k_dec_radix, and RA8_INTERNAL.

Referenced by internal_usb_audio_log_frames().

◆ internal_usb_audio_usb_or_halt()

void internal_usb_audio_usb_or_halt ( void )

static

Bring up USB-FS pin mux + UAC1 class layer + format/volume shadows.

Pin-mux first, then ra8_nsc_usb_init to release the MSTP gate, then ra8_usb_paud_init to install the iso-IN / iso-OUT pipes, then ra8_usb_paud_set_format / ra8_usb_paud_set_volume to seed the format + volume shadows, then ra8_nsc_usb_attach to raise the D+ pull-up so the host begins enumeration.

Precondition: Clocks + SCI8 already initialized.; USB device pins are available to the board support package.

Postcondition: USB-FS device-mode UAC1 endpoint is live.; Format and volume shadows contain the demo's fixed audio settings.

Note: D+ attachment is deliberately the final operation so the host cannot enumerate a partially configured audio class.

Since: 0.1.0

Definition at line 343 of file main.c.

References internal_usb_audio_panic_halt(), k_ra8_ok, k_ra8_usb_speed_fs, k_usb_audio_bytes_per_samp, k_usb_audio_channels, k_usb_audio_sample_rate_hz, k_usb_audio_volume_0_db, ra8_board_usbhs_device_init(), RA8_INTERNAL, ra8_nsc_usb_attach(), ra8_usb_paud_init(), ra8_usb_paud_set_format(), and ra8_usb_paud_set_volume().

Referenced by internal_usb_audio_setup_or_halt().

◆ main()

void main ( void )

Application entry.

The application entry point Reset_Handler hands control to.

Brings up CGC + USB-FS + UAC1, then enters the iso-IN feed loop forever.

Precondition: Reset_Handler has copied .data and zeroed .bss.; SystemInit has set VTOR, FPU, and priority grouping.

Postcondition: On clean entry the CPU stays in the iso-IN feed loop forever.; On any HAL init failure the function halts in WFI.

Since: 0.1.0

Definition at line 464 of file main.c.

References internal_usb_audio_log(), internal_usb_audio_log_frames(), internal_usb_audio_panic_halt(), internal_usb_audio_send_one_frame(), internal_usb_audio_setup_or_halt(), k_ra8_ok, k_usb_audio_idle_step_ms, k_usb_audio_log_period, ra8_delay_ms(), and ra8_isr_globals_enable().

Variable Documentation

◆ s_usb_audio_sine_lut

const uint8_t s_usb_audio_sine_lut[k_usb_audio_lut_bytes]

static

1 kHz sine LUT, 48 stereo 16-bit samples per cycle.

Each entry is interleaved L/R 16-bit little-endian (USB Audio 1.0 sec 2.2.5 Format Type-I sample byte order). The amplitude is 0x4000 (half full-scale) so the host can downstream-mix without clipping. Hand-computed with sin(2*pi*n/48) at integer step 1 of 48; floating-point math is forbidden in this firmware so the LUT is precomputed and stored in MRAM as constant rodata.

Index 0 = sin(0), 12 = sin(pi/2) = +0x4000, 24 = sin(pi) = 0, 36 = sin(3pi/2) = -0x4000, ... back to 0 at index 48.

Definition at line 136 of file main.c.

Referenced by internal_usb_audio_send_one_frame().

Enumerations

Functions

Variables

Detailed Description

Pinout (USB-FS, EK-RA8D2 v1)

Sequence

Enumeration Type Documentation

◆ usb_audio_config_t

◆ usb_audio_format_t

◆ usb_audio_volume_t

Function Documentation

◆ internal_usb_audio_clocks_or_halt()

◆ internal_usb_audio_log()

◆ internal_usb_audio_log_frames()

◆ internal_usb_audio_panic_halt()

◆ internal_usb_audio_send_one_frame()

◆ internal_usb_audio_setup_or_halt()

◆ internal_usb_audio_u32_to_ascii()

◆ internal_usb_audio_usb_or_halt()

◆ main()

Variable Documentation

◆ s_usb_audio_sine_lut