This API is used to perform asynchronous operations.

Overview

Asynchronous transfers are performed by submitting previously prepared transfer handle (usb_host_transfer_h). When the transfer is finished, the callback set by user is called. Transfer handle contains all transfer parameters and, when configured, can be submitted multiple times. Most of parameters required for asynchronous transfers match those from synchronous transfer.

Like in synchronous transfer, you must first obtain the endpoint handle. Then you can create a transfer handle with desired parameters.

 usb_host_transfer_h transfer;
 usb_host_endpoint_h ep;

 // Obtain the endpoint ep
 // ...

 // Create a transfer handle
 ret = usb_host_create_transfer(ep, transfer_callback, data, length, user_data, timeout, &transfer);
 if (ret < 0)
     error();

 // Submit the transfer
 ret = usb_host_transfer_submit(transfer);
 if (ret < 0)
     error();

 // ...
 // Destroy the transfer handle when no longer needed
 ret = usb_host_transfer_destroy(transfer);

The transfer_callback() is a function which will be called when transfer is finished. It should match the usb_host_transfer_cb() type, e.g.:

 void transfer_callback(usb_host_transfer_h transfer, void user_data)
 {
    int status;
    int length;
    char *data;

    // Get the status value
    usb_host_transfer_get_status(transfer, &status);

    // Check the status value
    if (status != USB_HOST_TRANSFER_COMPLETED) {
        // Handle errors here
    }

    // Get the data buffer
    usb_host_transfer_get_data(transfer, &data, &length);

    // Handle received data
    // ...
 }

Note, that not always successfully submitted transfer finishes with success. The callback function is called with status code set to value from usb_host_transfer_status_e enum. It informs what happened with the transfer.

Also remember, that received data length can be different than length of buffer (i.e. requested length).

You can change the transfer handle parameters by using usb_host_transfer_set_* functions and resubmit the transfer multiple times.

 void transfer_callback(usb_host_transfer_h transfer, void user_data)
 {
    // Change parameters of the transfer if needed
    // ...

    usb_host_transfer_submit(transfer);
 }

For passing additional data to callback function user_data pointer can be used. The user_data passed to callback is the same as was set for submitted transfer.

After transfer is submitted, it can be canceled by calling usb_host_transfer_cancel(). This will cause the transfer callback function to be called with USB_HOST_TRANSFER_CANCELLED status.

Isochronous transfers

For creating isochronous transfers use usb_host_create_isochronous_transfer() function. It takes parameters similar to usb_host_create_transfer(), with addition of num_iso_packets. The data buffer is used to store all packets data and should be large enough to do so.

 ret = usb_host_create_isochronous_transfer(ep, transfer_callback, data, length, num_iso_packets, user_data, timeout, &transfer);

Before submitting the transfer you must setup isochronous packets lengths (and data, if making out transfer).

 for (i = 0; i < num_iso_packets; ++i) {
    ret = usb_host_transfer_set_iso_packet_length(transfer, i, packet_lenght);
    //...

    ret = usb_host_transfer_get_iso_packet_data(transfer, i, &data, &len);
    // fill received buffer with your data
    // ...
 }

Similarly, you can obtain received data in callback function by calling usb_host_transfer_get_iso_packet_data(). Note, that length of received data can be different than length of buffer space set for an isochronous packet.

Each packet has its own status code. Check them by calling usb_host_transfer_get_iso_packet_status().

Control transfers

You can make asynchronous control transfers as well. They use the same data type as other asynchronous transfers (usb_host_transfer_h) and can be handled in similar way.

A control transfer need specific format of data in buffer, i.e. first 8 bytes of buffer need to contain a setup packet. You can find more informations about setup packets in usb protocol specification. This API provides functions helping with filling the setup packet.

 // Create a transfer handle
 ret = usb_host_create_control_transfer(dev, transfer_callback, data, length, user_data, timeout, &transfer);
 if (ret < 0)
     error();

 // Set setup packet member values

 usb_host_control_transfer_set_request_type(transfer, bm_request_type);
 usb_host_control_transfer_set_request(transfer, b_request);
 usb_host_control_transfer_set_value(transfer, w_value);
 usb_host_control_transfer_set_index(transfer, w_index);

 // Submit the transfer
 ret = usb_host_transfer_submit(transfer);
 if (ret < 0)
     error();

 // ...
 // Destroy the transfer handle when no longer needed
 ret = usb_host_transfer_destroy(transfer);

When receiving data from control transfer, remember that first 8 bytes of buffer are filled with setup packet. To obtain pointer to actual data, use usb_host_control_transfer_get_data().

Functions
int	usb_host_create_transfer (usb_host_endpoint_h ep, usb_host_transferred_cb callback, unsigned char data, int length, void user_data, unsigned int timeout, usb_host_transfer_h *transfer)
	Prepares an asynchronous USB transfer.
int	usb_host_create_isochronous_transfer (usb_host_endpoint_h ep, usb_host_transferred_cb callback, unsigned char data, int length, unsigned int num_iso_packets, void user_data, unsigned int timeout, usb_host_transfer_h *transfer)
	Prepares an asynchronous USB isochronous transfer.
int	usb_host_create_control_transfer (usb_host_device_h dev, usb_host_transferred_cb callback, unsigned char data, int length, void user_data, unsigned int timeout, usb_host_transfer_h *transfer)
	Prepares an asynchronous USB control transfer.
int	usb_host_transfer_set_ep (usb_host_transfer_h transfer, usb_host_endpoint_h ep)
	Sets an endpoint for asynchronous transfer.
int	usb_host_transfer_set_callback (usb_host_transfer_h transfer, usb_host_transferred_cb callback)
	Sets a callback for asynchronous transfer.
int	usb_host_transfer_set_data (usb_host_transfer_h transfer, unsigned char *data, int length)
	Sets data buffer for asynchronous transfer.
int	usb_host_transfer_set_timeout (usb_host_transfer_h transfer, unsigned int timeout)
	Sets timeout for asynchronous transfer.
int	usb_host_transfer_set_num_iso_packets (usb_host_transfer_h transfer, unsigned int num_iso_packets)
	Sets number of isochronous packet for isochronous transfer.
int	usb_host_control_transfer_set_request_type (usb_host_transfer_h transfer, uint8_t bm_request_type)
	Sets request type for control transfer setup packet.
int	usb_host_control_transfer_set_request (usb_host_transfer_h transfer, uint8_t b_request)
	Sets request field for control transfer setup packet.
int	usb_host_control_transfer_set_value (usb_host_transfer_h transfer, uint16_t w_value)
	Sets w_value field for control transfer setup packet.
int	usb_host_control_transfer_set_index (usb_host_transfer_h transfer, uint16_t w_index)
	Sets w_index field for control transfer setup packet.
int	usb_host_transfer_get_status (usb_host_transfer_h transfer, int *status)
	Gets the transfer status.
int	usb_host_transfer_get_data (usb_host_transfer_h transfer, unsigned char *data, unsigned int actual_length)
	Gets the transfer data.
int	usb_host_control_transfer_get_data (usb_host_transfer_h transfer, unsigned char *data, unsigned int actual_length)
	Gets the control transfer data.
int	usb_host_transfer_get_length (usb_host_transfer_h transfer, unsigned int *length)
	Gets length of data buffer.
int	usb_host_transfer_get_num_iso_packets (usb_host_transfer_h transfer, unsigned int *num_iso_packets)
	Gets number of isochronous packets for this transfer.
int	usb_host_transfer_set_iso_packet_length (usb_host_transfer_h transfer, unsigned int packet_number, int length)
	Sets an isochronous packet length.
int	usb_host_transfer_get_iso_packet_status (usb_host_transfer_h transfer, unsigned int packet_number, int *status)
	Gets an isochronous packet status.
int	usb_host_transfer_get_iso_packet_data (usb_host_transfer_h transfer, unsigned int packet_number, unsigned char *data, int actual_length)
	Gets data buffer of isochronous packet.
int	usb_host_transfer_get_iso_packet_length (usb_host_transfer_h transfer, unsigned int packet_number, int *length)
	Gets isochronous packet data buffer length.
int	usb_host_transfer_destroy (usb_host_transfer_h transfer)
	Destroys an asynchronous transfer structure.
int	usb_host_transfer_submit (usb_host_transfer_h transfer)
	Submits an asynchronous USB transfer.
int	usb_host_transfer_cancel (usb_host_transfer_h transfer)
	Cancels an asynchronous USB transfer.
Typedefs
typedef struct usb_host_transfer_s *	usb_host_transfer_h
	USB asynchronous transfer handle.
typedef void(*	usb_host_transferred_cb )(usb_host_transfer_h transfer, void *user_data)
	Called when asynchronous transfers finishes.

Typedef Documentation

typedef struct usb_host_transfer_s* usb_host_transfer_h

USB asynchronous transfer handle.

This type represents an asynchronous USB transfer.

Since :: 5.0

typedef void(* usb_host_transferred_cb)(usb_host_transfer_h transfer, void *user_data)

Called when asynchronous transfers finishes.

Since :: 5.0

Parameters:

[in]	transfer	Transfer for which this callback was set
[in]	user_data	User data pointer passed on callback registration

Enumeration Type Documentation

enum usb_host_transfer_status_e

Enumeration of transfer status codes.

Since :: 5.0

Enumerator:

USB_HOST_TRANSFER_COMPLETED	Transfer completed without error
USB_HOST_TRANSFER_ERROR	Transfer failed
USB_HOST_TRANSFER_TIMED_OUT	Transfer timed out
USB_HOST_TRANSFER_CANCELLED	Transfer cancelled
USB_HOST_TRANSFER_STALL	Halt condition detected
USB_HOST_TRANSFER_NO_DEVICE	Device was disconnected
USB_HOST_TRANSFER_OVERFLOW	Device sent more data than requested
USB_HOST_TRANSFER_UNKNOWN	Unknown status

Function Documentation

int usb_host_control_transfer_get_data	(	usb_host_transfer_h	transfer,
		unsigned char **	data,
		unsigned int *	actual_length
	)

Gets the *control* transfer data.

Since :: 5.0

Remarks:: data is part of the transfer object and should not be released separately. It should not be accessed after transfer is destroyed.

Parameters:

[in]	transfer	Control transfer handle
[out]	data	Data buffer of this transfer
[out]	actual_length	Actual length of transferred data

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed

int usb_host_control_transfer_set_index	(	usb_host_transfer_h	transfer,
		uint16_t	w_index
	)

Sets w_index field for control transfer setup packet.

Since :: 5.0

Parameters:

[in]	transfer	A transfer handle
[in]	w_index	wIndex field for the setup packet

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed

Precondition:: transfer should be created by usb_host_create_control_transfer().

int usb_host_control_transfer_set_request	(	usb_host_transfer_h	transfer,
		uint8_t	b_request
	)

Sets request field for control transfer setup packet.

Since :: 5.0

Parameters:

[in]	transfer	A transfer handle
[in]	b_request	bRequest field for the setup packet

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed

Precondition:: transfer should be created by usb_host_create_control_transfer().

int usb_host_control_transfer_set_request_type	(	usb_host_transfer_h	transfer,
		uint8_t	bm_request_type
	)

Sets request type for control transfer setup packet.

Since :: 5.0

Parameters:

[in]	transfer	A transfer handle
[in]	bm_request_type	bmRequestType type field for the setup packet

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed

Precondition:: transfer should be created by usb_host_create_control_transfer().

int usb_host_control_transfer_set_value	(	usb_host_transfer_h	transfer,
		uint16_t	w_value
	)

Sets w_value field for control transfer setup packet.

Since :: 5.0

Parameters:

[in]	transfer	A transfer handle
[in]	w_value	wValue field for the setup packet

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed

Precondition:: transfer should be created by usb_host_create_control_transfer().

int usb_host_create_control_transfer	(	usb_host_device_h	dev,
		usb_host_transferred_cb	callback,
		unsigned char *	data,
		int	length,
		void *	user_data,
		unsigned int	timeout,
		usb_host_transfer_h *	transfer
	)

Prepares an asynchronous USB control transfer.

This function prepares control transfer handle. Transfer handle can be used for multiple transfers after this initialization. Note, that first 8 bytes of data buffer are interpreted as control setup packet. You may use usb_host_control_transfer_set_* functions to set the setup packet fields.

Since :: 5.0

Parameters:

[in]	dev	Device handle
[in]	callback	Callback to be called when transfer is finished
[in]	data	Suitably-sized data buffer
[in]	length	For writes, the number of bytes from data to be sent, for reads, the maximum number of bytes to receive into the data buffer
[in]	user_data	Pointer to data which will be passed to callback function later on
[in]	timeout	Timeout (in milliseconds) that transfer should wait before giving up due to no response being received (for an unlimited timeout use value of 0)
[out]	transfer	Transfer handle

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed
USB_HOST_ERROR_OUT_OF_MEMORY	Out of memory

Precondition:: dev must be an opened device handle

Postcondition:: transfer should be destroyed by calling usb_host_transfer_destroy() when it's no longer needed.

int usb_host_create_isochronous_transfer	(	usb_host_endpoint_h	ep,
		usb_host_transferred_cb	callback,
		unsigned char *	data,
		int	length,
		unsigned int	num_iso_packets,
		void *	user_data,
		unsigned int	timeout,
		usb_host_transfer_h *	transfer
	)

Prepares an asynchronous USB isochronous transfer.

This function prepares transfer handle for asynchronous communication. Usage is similar to usb_host_create_transfer(), except this function is intended for isochronous endpoints. Transfer handle can be used for multiple transfers after this initialization. Note however, that this function needs to allocate memory for num_iso_packets isochronous packets and it will be the limit for number of them in this transfer.

Since :: 5.0

Parameters:

[in]	ep	Endpoint handle
[in]	callback	Callback to be called when transfer is finished
[in]	data	Suitably-sized data buffer, similar to synchronized transfer
[in]	length	For writes, the number of bytes from data to be sent; for reads, the maximum number of bytes to receive into the data buffer
[in]	num_iso_packets	Number of isochronous packets
[in]	user_data	Pointer to data which will be passed to callback function later on
[in]	timeout	Timeout (in milliseconds) that transfer should wait before giving up due to no response being received (for an unlimited timeout use value of 0)
[out]	transfer	Transfer handle

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed
USB_HOST_ERROR_OUT_OF_MEMORY	Out of memory

Precondition:: ep must be a valid endpoint received from usb_host_interface_get_endpoint().

Postcondition:: transfer should be destroyed by calling usb_host_transfer_destroy() when it's no longer needed.

int usb_host_create_transfer	(	usb_host_endpoint_h	ep,
		usb_host_transferred_cb	callback,
		unsigned char *	data,
		int	length,
		void *	user_data,
		unsigned int	timeout,
		usb_host_transfer_h *	transfer
	)

Prepares an asynchronous USB transfer.

This function prepares transfer handle for asynchronous communication. Transfer handle can be used for multiple transfers after this initialization.

Since :: 5.0

Parameters:

[in]	ep	Endpoint handle
[in]	callback	Callback to be called when transfer is finished
[in]	data	Suitably-sized data buffer, similar to synchronized transfer
[in]	length	For writes, the number of bytes from data to be sent; for reads, the maximum number of bytes to receive into the data buffer
[in]	user_data	Pointer to data which will be passed to callback function later on
[in]	timeout	Timeout (in milliseconds) that transfer should wait before giving up due to no response being received (for an unlimited timeout use value of 0)
[out]	transfer	Transfer handle

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed
USB_HOST_ERROR_OUT_OF_MEMORY	Out of memory

Precondition:: ep must be a valid endpoint received from usb_host_interface_get_endpoint().

Postcondition:: transfer should be destroyed by calling usb_host_transfer_destroy() when it's no longer needed.

int usb_host_transfer_cancel ( usb_host_transfer_h transfer )

Cancels an asynchronous USB transfer.

After calling this function the transfer will be cancelled, if only it was not finished already. The transfer callback will be called with USB_HOST_TRANSFER_CANCELLED status.

Since :: 5.0

Parameters:

[in] transfer Transfer handle to be cancelled

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed

int usb_host_transfer_destroy ( usb_host_transfer_h transfer )

Destroys an asynchronous transfer structure.

When no longer needed, transfer should be destroyed by this function. It frees memory allocated for the transfer. You cannot destroy unfinished transfer, wait for its completion or cancel it.

Since :: 5.0

Parameters:

[in] transfer Transfer handle to be destroyed

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed

int usb_host_transfer_get_data	(	usb_host_transfer_h	transfer,
		unsigned char **	data,
		unsigned int *	actual_length
	)

Gets the transfer data.

Since :: 5.0

Remarks:: data is part of the transfer object and should not be released separately. It should not be accessed after transfer is destroyed.

Parameters:

[in]	transfer	Transfer handle
[out]	data	Data buffer of this transfer
[out]	actual_length	Actual length of transferred data

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed

int usb_host_transfer_get_iso_packet_data	(	usb_host_transfer_h	transfer,
		unsigned int	packet_number,
		unsigned char **	data,
		int *	actual_length
	)

Gets data buffer of isochronous packet.

Since :: 5.0

Remarks:: data is part of the transfer object and should not be released separately. It should not be accessed after transfer is destroyed.

Parameters:

[in]	transfer	Transfer handle
[in]	packet_number	Number of isochronous packet
[out]	data	Data buffer for this packet
[out]	actual_length	Length of transferred data

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed
USB_HOST_ERROR_NOT_FOUND	Packet of given number not found

int usb_host_transfer_get_iso_packet_length	(	usb_host_transfer_h	transfer,
		unsigned int	packet_number,
		int *	length
	)

Gets isochronous packet data buffer length.

Since :: 5.0

Parameters:

[in]	transfer	Transfer handle
[in]	packet_number	Number of isochronous packet
[out]	length	Length of data buffer

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed
USB_HOST_ERROR_NOT_FOUND	Packet of given number not found

int usb_host_transfer_get_iso_packet_status	(	usb_host_transfer_h	transfer,
		unsigned int	packet_number,
		int *	status
	)

Gets an isochronous packet status.

Since :: 5.0

Parameters:

[in]	transfer	Transfer handle
[in]	packet_number	Number of isochronous packet
[out]	status	Status of selected packet

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed
USB_HOST_ERROR_NOT_FOUND	Packet of given number not found

int usb_host_transfer_get_length	(	usb_host_transfer_h	transfer,
		unsigned int *	length
	)

Gets length of data buffer.

This functions gets length that was set for data buffer, not the actual transferred data length. For length of transferred data see usb_host_transfer_get_data().

Since :: 5.0

Parameters:

[in]	transfer	Transfer handle
[out]	length	Length of data buffer for this transfer

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed

int usb_host_transfer_get_num_iso_packets	(	usb_host_transfer_h	transfer,
		unsigned int *	num_iso_packets
	)

Gets number of isochronous packets for this transfer.

Since :: 5.0

Parameters:

[in]	transfer	Transfer handle
[out]	num_iso_packets	Number of isochronous packets

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed

int usb_host_transfer_get_status	(	usb_host_transfer_h	transfer,
		int *	status
	)

Gets the transfer status.

Since :: 5.0

Parameters:

[in]	transfer	Transfer handle
[out]	status	Status of this transfer

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed

int usb_host_transfer_set_callback	(	usb_host_transfer_h	transfer,
		usb_host_transferred_cb	callback
	)

Sets a callback for asynchronous transfer.

This function changes the callback to be called on transfer completion.

Since :: 5.0

Parameters:

[in]	transfer	A transfer handle
[in]	callback	A callback function

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed

Precondition:: transfer should be created by usb_host_create_transfer() or usb_host_create_isochronous_transfer().

int usb_host_transfer_set_data	(	usb_host_transfer_h	transfer,
		unsigned char *	data,
		int	length
	)

Sets data buffer for asynchronous transfer.

This function changes the data buffer used for this transfer.

Since :: 5.0

Parameters:

[in]	transfer	A transfer handle
[in]	data	A data buffer
[in]	length	Length of data buffer

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed

Precondition:: transfer should be created by usb_host_create_transfer() or usb_host_create_isochronous_transfer().

int usb_host_transfer_set_ep	(	usb_host_transfer_h	transfer,
		usb_host_endpoint_h	ep
	)

Sets an endpoint for asynchronous transfer.

This function changes the endpoint on which given transfer is performed. Next submissions will be performed on this endpoint.

Since :: 5.0

Parameters:

[in]	transfer	A transfer handle
[in]	ep	An endpoint handle

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed

Precondition:: transfer should be created by usb_host_create_transfer() or usb_host_create_isochronous_transfer().

int usb_host_transfer_set_iso_packet_length	(	usb_host_transfer_h	transfer,
		unsigned int	packet_number,
		int	length
	)

Sets an isochronous packet length.

This function sets length of individual packet.

Since :: 5.0

Parameters:

[in]	transfer	Transfer handle
[in]	packet_number	Number of isochronous packet
[in]	length	Length of the packet handle

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed
USB_HOST_ERROR_NOT_FOUND	Packet of given number not found
USB_HOST_ERROR_OVERFLOW	Not enough space for this packet in data buffer

int usb_host_transfer_set_num_iso_packets	(	usb_host_transfer_h	transfer,
		unsigned int	num_iso_packets
	)

Sets number of isochronous packet for isochronous transfer.

This function changes the number of isochronous packets in transfer. This parameter affects only isochronous transfers (i.e. transfers on isochronous endpoints). Use usb_host_endpoint_get_transfer_type() for checking types of your endpoints.

Since :: 5.0

Parameters:

[in]	transfer	A transfer handle
[in]	num_iso_packets	Number of isochronous packets in this transfer

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed
USB_HOST_ERROR_OUT_OF_MEMORY	Out of memory (too many packets)

Precondition:: transfer should be created by usb_host_create_transfer() or usb_host_create_isochronous_transfer().

int usb_host_transfer_set_timeout	(	usb_host_transfer_h	transfer,
		unsigned int	timeout
	)

Sets timeout for asynchronous transfer.

This function changes the timeout after which transfer will be stopped due to no response being received.

Since :: 5.0

Parameters:

[in]	transfer	A transfer handle
[in]	timeout	A timeout in milliseconds

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed

Precondition:: transfer should be created by usb_host_create_transfer() or usb_host_create_isochronous_transfer().

int usb_host_transfer_submit ( usb_host_transfer_h transfer )

Submits an asynchronous USB transfer.

Calling this will start actual transfer.

Since :: 5.0

Parameters:

[in] transfer Transfer handle to be submitted

Returns:: 0 on success, negative error code on error

Return values:

USB_HOST_ERROR_NONE	Successful
USB_HOST_ERROR_NOT_SUPPORTED	Not supported
USB_HOST_ERROR_INVALID_PARAMETER	Invalid parameter was passed

Precondition:: transfer should be initialized by one of initialization functions: usb_host_create_transfer(), usb_host_create_isochronous_transfer() or usb_host_create_control_transfer().

Overview

Isochronous transfers

Control transfers

Functions

Typedefs

Typedef Documentation

Enumeration Type Documentation

Function Documentation