These functions comprise the core of libusb. They are used by all applications that utilize libusb. usb_init Initialize libusb void usb_init Just like the name implies, usb_init sets up some internal structures. usb_init must be called before any other libusb functions. usb_find_busses Finds all USB busses on system int usb_find_busses usb_find_busses will find all of the busses on the system. Returns the number of changes since previous call to this function (total of new busses and busses removed). usb_find_devices Find all devices on all USB devices int usb_find_devices usb_find_devices will find all of the devices on each bus. This should be called after . Returns the number of changes since the previous call to this function (total of new device and devices removed). usb_get_busses Return the list of USB busses found struct usb_bus *usb_get_busses usb_get_busses simply returns the value of the global variable usb_busses. This was implemented for those languages that support C calling convention and can use shared libraries, but don't support C global variables (like Delphi). This group of functions deal with the device. It allows you to open and close the device as well standard USB operations like setting the configuration, alternate settings, clearing halts and resetting the device. It also provides OS level operations such as claiming and releasing interfaces. usb_open Opens a USB device usb_dev_handle *usb_open struct *usb_device dev usb_open is to be used to open up a device for use. usb_open must be called before attempting to perform any operations to the device. Returns a handle used in future communication with the device. usb_close Closes a USB device int usb_close usb_dev_handle *dev usb_close closes a device opened with . No further operations may be performed on the handle after usb_close is called. Returns 0 on success or < 0 on error. usb_set_configuration Sets the active configuration of a device int usb_set_configuration usb_dev_handle *dev int configuration usb_set_configuration sets the active configuration of a device. The configuration parameter is the value as specified in the descriptor field bConfigurationValue. Returns 0 on success or < 0 on error. usb_set_altinterface Sets the active alternate setting of the current interface int usb_set_altinterface usb_dev_handle *dev int alternate usb_set_altinterface sets the active alternate setting of the current interface. The alternate parameter is the value as specified in the descriptor field bAlternateSetting. Returns 0 on success or < 0 on error. usb_resetep Resets state for an endpoint int usb_resetep usb_dev_handle *dev unsigned int ep usb_resetep resets all state (like toggles) for the specified endpoint. The ep parameter is the value specified in the descriptor field bEndpointAddress. Returns 0 on success or < 0 on error. usb_resetep is deprecated. You probably want to use . usb_clear_halt Clears any halt status on an endpoint int usb_clear_halt usb_dev_handle *dev unsigned int ep usb_clear_halt clears any halt status on the specified endpoint. The ep parameter is the value specified in the descriptor field bEndpointAddress. Returns 0 on success or < 0 on error. usb_reset Resets a device int usb_reset usb_dev_handle *dev usb_reset resets the specified device by sending a RESET down the port it is connected to. Returns 0 on success or < 0 on error. After calling usb_reset, the device will need to re-enumerate and thusly, requires you to find the new device and open a new handle. The handle used to call usb_reset will no longer work. usb_claim_interface Claim an interface of a device int usb_claim_interface usb_dev_handle *dev int interface usb_claim_interface claims the interface with the Operating System. The interface parameter is the value as specified in the descriptor field bInterfaceNumber. Returns 0 on success or < 0 on error. usb_claim_interface must be called before you perform any operations related to this interface (like , , etc). code description -EBUSY Interface is not available to be claimed -ENOMEM Insufficient memory usb_release_interface Releases a previously claimed interface int usb_release_interface usb_dev_handle *dev int interface usb_release_interface releases an interface previously claimed with . The interface parameter is the value as specified in the descriptor field bInterfaceNumber. Returns 0 on success or < 0 on error. This group of functions allow applications to send messages to the default control pipe. usb_control_msg Send a control message to a device int usb_control_msg usb_dev_handle *dev int requesttype int request int value int index char *bytes int size int timeout usb_control_msg performs a control request to the default control pipe on a device. The parameters mirror the types of the same name in the USB specification. Returns number of bytes written/read or < 0 on error. usb_get_string Retrieves a string descriptor from a device int usb_get_string usb_dev_handle *dev int index int langid char *buf size_t buflen usb_get_string retrieves the string descriptor specified by index and langid from a device. The string will be returned in Unicode as specified by the USB specification. Returns the number of bytes returned in buf or < 0 on error. usb_get_string_simple Retrieves a string descriptor from a device using the first language int usb_get_string_simple usb_dev_handle *dev int index char *buf size_t buflen usb_get_string_simple is a wrapper around usb_get_string that retrieves the string description specified by index in the first language for the descriptor and converts it into C style ASCII. Returns number of bytes returned in buf or < 0 on error. usb_get_descriptor Retrieves a descriptor from a device's default control pipe int usb_get_descriptor usb_dev_handle *dev unsigned char type unsigned char index void *buf int size usb_get_descriptor retrieves a descriptor from the device identified by the type and index of the descriptor from the default control pipe. Returns number of bytes read for the descriptor or < 0 on error. See for a function that allows the control endpoint to be specified. usb_get_descriptor_by_endpoint Retrieves a descriptor from a device int usb_get_descriptor_by_endpoint usb_dev_handle *dev int ep unsigned char type unsigned char index void *buf int size usb_get_descriptor_by_endpoint retrieves a descriptor from the device identified by the type and index of the descriptor from the control pipe identified by ep. Returns number of bytes read for the descriptor or < 0 on error. This group of functions allow applications to send and receive data via bulk pipes. usb_bulk_write Write data to a bulk endpoint int usb_bulk_write usb_dev_handle *dev int ep char *bytes int size int timeout usb_bulk_write performs a bulk write request to the endpoint specified by ep. Returns number of bytes written on success or < 0 on error. usb_bulk_read Read data from a bulk endpoint int usb_bulk_read usb_dev_handle *dev int ep char *bytes int size int timeout usb_bulk_read performs a bulk read request to the endpoint specified by ep. Returns number of bytes read on success or < 0 on error. This group of functions allow applications to send and receive data via interrupt pipes. usb_interrupt_write Write data to an interrupt endpoint int usb_interrupt_write usb_dev_handle *dev int ep char *bytes int size int timeout usb_interrupt_write performs an interrupt write request to the endpoint specified by ep. Returns number of bytes written on success or < 0 on error. usb_interrupt_read Read data from a interrupt endpoint int usb_interrupt_read usb_dev_handle *dev int ep char *bytes int size int timeout usb_interrupt_read performs a interrupt read request to the endpoint specified by ep. Returns number of bytes read on success or < 0 on error. These functions are non portable. They may expose some part of the USB API on one OS or perhaps a couple, but not all. They are all marked with the string _np at the end of the function name. A C preprocessor macro will be defined if the function is implemented. The form is LIBUSB_HAS_ prepended to the function name, without the leading "usb_", in all caps. For example, if usb_get_driver_np is implemented, LIBUSB_HAS_GET_DRIVER_NP will be defined. usb_get_driver_np Get driver name bound to interface int usb_get_driver_np usb_dev_handle *dev int interface char *name int namelen This function will obtain the name of the driver bound to the interface specified by the parameter interface and place it into the buffer named name limited to namelen characters. Returns 0 on success or < 0 on error. Implemented on Linux only. usb_detach_kernel_driver_np Detach kernel driver from interface int usb_detach_kernel_driver_np usb_dev_handle *dev int interface This function will detach a kernel driver from the interface specified by parameter interface. Applications using libusb can then try claiming the interface. Returns 0 on success or < 0 on error. Implemented on Linux only.