cdc_rx.c File Reference

USB CDC receive ring buffer implementation. More...

#include "icarus/cdc_rx.h"
#include "icarus/config.h"
#include <stddef.h>

Go to the source code of this file.

Functions
void	__cdc_rx_init (void)
void	__cdc_rx_push (const uint8_t *data, uint32_t len)
bool	__cdc_rx_read_byte (uint8_t *out)
uint32_t	__cdc_rx_available (void)

Variables
static volatile uint8_t	rx_buf [512]
static volatile uint32_t	rx_head
static volatile uint32_t	rx_tail

Detailed Description

USB CDC receive ring buffer implementation.

SPSC (single-producer single-consumer) ring buffer. Producer: CDC_Receive_FS callback (USB interrupt context). Consumer: any RTOS task draining bytes.

The buffer and indices live in DTCM_DATA_PRIV (privileged-only tightly-coupled memory). Public read accessors go through SVC gates (SVC_CDC_RX_READ_BYTE / SVC_CDC_RX_AVAILABLE) so unprivileged thread-mode tasks can use them once the MPU is locked. The producer call site is the USB CDC ISR, which is already in privileged handler context — it calls the __cdc_rx_push privileged variant directly to avoid issuing an SVC from a high-priority interrupt.

Author

Souham Biswas

Date

2026

Copyright

Copyright 2025-2026 Souham Biswas https://github.com/ironhide23586/icarus-os-core Licensed under the Apache License, Version 2.0

Definition in file cdc_rx.c.

Function Documentation

__cdc_rx_available()

uint32_t __cdc_rx_available

(

void

)

Definition at line 66 of file cdc_rx.c.

References CDC_RX_BUF_SIZE, rx_head, and rx_tail.

Referenced by cdc_rx_available(), and SVC_Handler_C().

__cdc_rx_init()

void __cdc_rx_init

(

void

)

Definition at line 38 of file cdc_rx.c.

References rx_head, and rx_tail.

Referenced by cdc_rx_init(), and SVC_Handler_C().

__cdc_rx_push()

void __cdc_rx_push	(	const uint8_t *	data,
		uint32_t	len
	)

Definition at line 43 of file cdc_rx.c.

References CDC_RX_BUF_SIZE, rx_buf, rx_head, and rx_tail.

Referenced by cdc_rx_push().

__cdc_rx_read_byte()

bool __cdc_rx_read_byte

(

uint8_t *

out

)

Definition at line 57 of file cdc_rx.c.

References CDC_RX_BUF_SIZE, rx_buf, rx_head, and rx_tail.

Referenced by cdc_rx_read_byte(), and SVC_Handler_C().

Variable Documentation

rx_buf

volatile uint8_t rx_buf[512]

static

Definition at line 32 of file cdc_rx.c.

Referenced by __cdc_rx_push(), and __cdc_rx_read_byte().

rx_head

volatile uint32_t rx_head

static

Definition at line 33 of file cdc_rx.c.

Referenced by __cdc_rx_available(), __cdc_rx_init(), __cdc_rx_push(), and __cdc_rx_read_byte().

rx_tail

volatile uint32_t rx_tail

static

Definition at line 34 of file cdc_rx.c.

Referenced by __cdc_rx_available(), __cdc_rx_init(), __cdc_rx_push(), and __cdc_rx_read_byte().