This is a generic low-level USB driver interface. More...

Detailed Description

This is a generic low-level USB driver interface.

About

usbdev specifies a common USB device API for low level USB interfaces. The interface is split in a definition for the USB interface hardware and for individual USB endpoints.

Design goals

Support for multiple instances on a single board
Interface optimized for MCU peripheral interfaces.

Details

The driver interface is split in two separate parts. One part is a global USB device interface, the other is an endpoint control API.

The usb device driver can manage parts of the USB interface itself such as the pull up resistor state or the USB speed.

The endpoint control API manages a single endpoint. This allows for a modular approach where multiple USB functions/interfaces can be multiplexed over a single USB interface. Each interface can be implemented as a separate module. The interface handler does not have to care about the usb device itself or it's endpoint number. It can simply request an available endpoint from the usb device with the usbdev_new_ep function.

Data transmission is done by requesting the endpoint with a max packet size. Memory for this buffer is allocated from dedicated memory of the MCU USB peripheral or from a buffer allocated by the peripheral specific usbdev struct. Received data from the host ends up at this buffer automatically by the low level drivers. Signalling that the data at the specified address is ready to be reused is done with the usbdev_ep_ready function by supplying a size of 0 for the len argument.

For transmitting data back to the host, a similar approach is used. The data to be transmitted is written to the specified address and the usbdev_ep_ready function is called with the size of the data as len argument.

This approach of setting the address and only indicating new data available is done to allow the low level USB peripheral to use DMA to transfer the data from and to the MCU memory.

A callback function is required for signalling events from the driver. The USBDEV_EVENT_ESR is special in that it indicates that the USB peripheral had an interrupt that needs to be serviced in a non-interrupt context. This requires the usbdev_esr function to be called. In the case that the event is signalled via the usbdev_t::epcb callback, the usbdev_ep_esr should be called to service the endpoint specific events from the peripheral.

Files
file	usbdev.h
	Definitions low-level USB driver interface.

Data Structures
struct	usbdev
	usbdev device descriptor More...

struct	usbdev_ep
	usbdev endpoint descriptor More...

struct	usbdev_driver
	usbdev driver functions More...

Macros
#define	USBDEV_EP_BUF_SPACE 1024
	Statically allocated buffer space for endpoints. More...

#define	USBDEV_NUM_ENDPOINTS 8
	Number of USB IN and OUT endpoints allocated. More...

Typedefs
typedef struct usbdev	usbdev_t
	usbdev_t forward declaration

typedef struct usbdev_ep	usbdev_ep_t
	usbdev_ep_t forward declaration

typedef void(*	usbdev_event_cb_t) (usbdev_t *usbdev, usbdev_event_t event)
	Event callback for signaling usbdev event to upper layers. More...

typedef void(*	usbdev_ep_event_cb_t) (usbdev_ep_t *ep, usbdev_event_t event)
	Event callback for signaling endpoint events to upper layers. More...

typedef struct usbdev_driver	usbdev_driver_t
	usbdev driver functions More...

Enumerations
enum	usbdev_event_t { USBDEV_EVENT_ESR = 1, USBDEV_EVENT_HOST_CONNECT, USBDEV_EVENT_HOST_DISCONNECT, USBDEV_EVENT_RESET, USBDEV_EVENT_SOF, USBDEV_EVENT_SUSPEND, USBDEV_EVENT_RESUME, USBDEV_EVENT_TR_COMPLETE, USBDEV_EVENT_TR_STALL, USBDEV_EVENT_TR_FAIL }
	List of event types that can be send from the device driver to the upper layer. More...

Functions
void	usbdev_init_lowlevel (void)
	Low level USB peripheral driver initialization. More...

usbdev_t *	usbdev_get_ctx (unsigned num)
	Retrieve usbdev context from the peripheral. More...

static void	usbdev_init (usbdev_t *dev)
	Initialize the USB peripheral device. More...

static usbdev_ep_t *	usbdev_new_ep (usbdev_t *dev, usb_ep_type_t type, usb_ep_dir_t dir, size_t buf_len)
	Retrieve an USB endpoint of the specified type. More...

static int	usbdev_get (usbdev_t dev, usbopt_t opt, void value, size_t max_len)
	Get an option value from a given usb device. More...

static int	usbdev_set (usbdev_t dev, usbopt_t opt, const void value, size_t value_len)
	Set an option value for a given usb device. More...

static void	usbdev_esr (usbdev_t *dev)
	a driver's user-space event service handler More...

static void	usbdev_ep_init (usbdev_ep_t *ep)
	Initialize the USB endpoint. More...

static int	usbdev_ep_get (usbdev_ep_t ep, usbopt_ep_t opt, void value, size_t max_len)
	Get an option value from a given usb device endpoint. More...

static int	usbdev_ep_set (usbdev_ep_t ep, usbopt_ep_t opt, const void value, size_t value_len)
	Set an option value for a given usb device endpoint. More...

static void	usbdev_ep_esr (usbdev_ep_t *ep)
	an endpoint's user-space event handler More...

static int	usbdev_ep_ready (usbdev_ep_t *ep, size_t len)
	Signal data buffer ready for data transmission. More...

Macro Definition Documentation

◆ USBDEV_EP_BUF_SPACE

#define USBDEV_EP_BUF_SPACE 1024

Statically allocated buffer space for endpoints.

When the device doesn't have dedicated memory for endpoint buffers, a buffer of this size is allocated to contain the endpoint buffers. Only needs to be as big as the total buffer space required by all endpoints

Definition at line 103 of file usbdev.h.

◆ USBDEV_NUM_ENDPOINTS

#define USBDEV_NUM_ENDPOINTS 8

Number of USB IN and OUT endpoints allocated.

Configures the number of endpoints allocated. An equal number of IN and OUT endpoints are allocated

Definition at line 113 of file usbdev.h.

Typedef Documentation

◆ usbdev_driver_t

typedef struct usbdev_driver usbdev_driver_t

usbdev driver functions

Helpers (such as usbdev_init) are provided and should be used instead. Directly calling these functions is not recommended.

◆ usbdev_ep_event_cb_t

typedef void(* usbdev_ep_event_cb_t) (usbdev_ep_t *ep, usbdev_event_t event)

Event callback for signaling endpoint events to upper layers.

Parameters

[in]	ep	usbdev endpoint context
[in]	event	type of the event

Definition at line 211 of file usbdev.h.

◆ usbdev_event_cb_t

typedef void(* usbdev_event_cb_t) (usbdev_t *usbdev, usbdev_event_t event)

Event callback for signaling usbdev event to upper layers.

Parameters

[in]	usbdev	usbdev context
[in]	event	type of the event

Definition at line 203 of file usbdev.h.

Enumeration Type Documentation

◆ usbdev_event_t

enum usbdev_event_t

List of event types that can be send from the device driver to the upper layer.

Enumerator
USBDEV_EVENT_ESR	Driver needs it's ESR (event service routine) handled.
USBDEV_EVENT_HOST_CONNECT	Host connection detected. A host has connected to the device. Detection should happen by detecting the USB power, but other detection mechanisms might be used.
USBDEV_EVENT_HOST_DISCONNECT	Host disconnected from the device. Similar to USBDEV_EVENT_HOST_CONNECT, except that the host disconnected instead.
USBDEV_EVENT_RESET	Line reset occurred. A line reset is a host initiated USB reset to the peripheral The peripheral driver must clears the following settings before emitting this event: Device address Endpoint configuration, including stall settings
USBDEV_EVENT_SOF	Start of Frame received. A Start of Frame (SoF) packet is received from the host.
USBDEV_EVENT_SUSPEND	USB suspend condition active.
USBDEV_EVENT_RESUME	USB suspend condition no longer active.
USBDEV_EVENT_TR_COMPLETE	Transaction completed event. An endpoint must emit this event after a transaction with the host occurred to indicate that the data in the buffer is used or new depending on the endpoint direction
USBDEV_EVENT_TR_STALL	Transaction stall event. An endpoint should emit this event after a stall reply has been transmitted to the host
USBDEV_EVENT_TR_FAIL	Transaction fail event. An endpoint should emit this event after a nack reply to the host.

Definition at line 120 of file usbdev.h.

Function Documentation

◆ usbdev_ep_esr()

static void usbdev_ep_esr ( usbdev_ep_t * ep )

inlinestatic

an endpoint's user-space event handler

See also: usbdev_driver_t::ep_esr

Precondition: (ep != NULL); (ep->dev != NULL)

Parameters

[in] ep USB endpoint descriptor to service

Definition at line 555 of file usbdev.h.

◆ usbdev_ep_get()

static int usbdev_ep_get	(	usbdev_ep_t *	ep,
		usbopt_ep_t	opt,
		void *	value,
		size_t	max_len
	)

inlinestatic

Get an option value from a given usb device endpoint.

See also: usbdev_driver_t::ep_get

Precondition: (ep != NULL); (ep->dev != NULL)

Parameters

[in]	ep	USB endpoint descriptor
[in]	opt	option type
[out]	value	pointer to store the option's value in
[in]	max_len	maximum number of byte that fit into `value`

Returns: number of bytes written to value; < 0 on error

Definition at line 513 of file usbdev.h.

◆ usbdev_ep_init()

static void usbdev_ep_init ( usbdev_ep_t * ep )

inlinestatic

Initialize the USB endpoint.

See also: usbdev_driver_t::ep_init

Precondition: (ep != NULL); (ep->dev != NULL)

Parameters

[in] ep USB endpoint descriptor

Definition at line 490 of file usbdev.h.

◆ usbdev_ep_ready()

static int usbdev_ep_ready	(	usbdev_ep_t *	ep,
		size_t	len
	)

inlinestatic

Signal data buffer ready for data transmission.

See also: usbdev_driver_t::ready

Precondition: (ep != NULL); (ep->dev != NULL)

Parameters

[in]	ep	USB endpoint descriptor
[in]	len	length of the data to be transmitted

Definition at line 573 of file usbdev.h.

◆ usbdev_ep_set()

static int usbdev_ep_set	(	usbdev_ep_t *	ep,
		usbopt_ep_t	opt,
		const void *	value,
		size_t	value_len
	)

inlinestatic

Set an option value for a given usb device endpoint.

See also: usbdev_driver_t::ep_set

Precondition: (ep != NULL); (ep->dev != NULL)

Parameters

[in]	ep	USB endpoint descriptor
[in]	opt	option type
[in]	value	pointer to the value
[in]	value_len	the length of `value`

Returns: number of bytes used from value; < 0 on error

Definition at line 537 of file usbdev.h.

◆ usbdev_esr()

static void usbdev_esr ( usbdev_t * dev )

inlinestatic

a driver's user-space event service handler

See also: usbdev_driver_t::esr

Precondition: (dev != NULL)

Parameters

[in] dev USB device descriptor

Definition at line 474 of file usbdev.h.

◆ usbdev_get()

static int usbdev_get	(	usbdev_t *	dev,
		usbopt_t	opt,
		void *	value,
		size_t	max_len
	)

inlinestatic

Get an option value from a given usb device.

See also: usbdev_driver_t::get

Precondition: (dev != NULL)

Parameters

[in]	dev	USB device descriptor
[in]	opt	option type
[out]	value	pointer to store the option's value in
[in]	max_len	maximal amount of byte that fit into `value`

Returns: number of bytes written to value; < 0 on error 0

Definition at line 436 of file usbdev.h.

◆ usbdev_get_ctx()

usbdev_t* usbdev_get_ctx ( unsigned num )

Retrieve usbdev context from the peripheral.

Parameters

num	usbdev peripheral number to retrieve

Returns: the usbdev context at index num

◆ usbdev_init()

static void usbdev_init ( usbdev_t * dev )

inlinestatic

Initialize the USB peripheral device.

See also: usbdev_driver_t::init

Precondition: (dev != NULL)

Parameters

dev	usb device to initialize

Definition at line 393 of file usbdev.h.

◆ usbdev_init_lowlevel()

void usbdev_init_lowlevel ( void )

Low level USB peripheral driver initialization.

This function prepares all usbdev peripherals available for initialization

◆ usbdev_new_ep()

static usbdev_ep_t* usbdev_new_ep	(	usbdev_t *	dev,
		usb_ep_type_t	type,
		usb_ep_dir_t	dir,
		size_t	buf_len
	)

inlinestatic

Retrieve an USB endpoint of the specified type.

See also: usbdev_driver_t::new_ep

Precondition: (dev != NULL)

Parameters

[in]	dev	USB device descriptor
[in]	type	USB endpoint type
[in]	dir	USB endpoint direction
[in]	buf_len	optimal USB endpoint buffer size

Returns: ptr to the new USB endpoint descriptor; NULL on error

Definition at line 414 of file usbdev.h.

◆ usbdev_set()

static int usbdev_set	(	usbdev_t *	dev,
		usbopt_t	opt,
		const void *	value,
		size_t	value_len
	)

inlinestatic

Set an option value for a given usb device.

See also: usbdev_driver_t::set

Precondition: (dev != NULL)

Parameters

[in]	dev	USB device descriptor
[in]	opt	option type
[in]	value	value to set
[in]	value_len	the length of `value`

Returns: number of bytes used from value; < 0 on error

Definition at line 458 of file usbdev.h.

Detailed Description

About

Design goals

Details

Files

Data Structures

Macros

Typedefs

Enumerations

Functions

Macro Definition Documentation

◆ USBDEV_EP_BUF_SPACE

◆ USBDEV_NUM_ENDPOINTS

Typedef Documentation

◆ usbdev_driver_t

◆ usbdev_ep_event_cb_t

◆ usbdev_event_cb_t

Enumeration Type Documentation

◆ usbdev_event_t

Function Documentation

◆ usbdev_ep_esr()

◆ usbdev_ep_get()

◆ usbdev_ep_init()

◆ usbdev_ep_ready()

◆ usbdev_ep_set()

◆ usbdev_esr()

◆ usbdev_get()

◆ usbdev_get_ctx()

◆ usbdev_init()

◆ usbdev_init_lowlevel()

◆ usbdev_new_ep()

◆ usbdev_set()