Functions

hidapi API

Functions

int HID_API_EXPORT HID_API_CALL hid_init (void)
 Initialize the HIDAPI library.
int HID_API_EXPORT HID_API_CALL hid_exit (void)
 Finalize the HIDAPI library.
struct hid_device_info
HID_API_EXPORT *HID_API_CALL 
hid_enumerate (unsigned short vendor_id, unsigned short product_id)
 Enumerate the HID Devices.
void HID_API_EXPORT HID_API_CALL hid_free_enumeration (struct hid_device_info *devs)
 Free an enumeration Linked List.
HID_API_EXPORT hid_device
*HID_API_CALL 
hid_open (unsigned short vendor_id, unsigned short product_id, const wchar_t *serial_number)
 Open a HID device using a Vendor ID (VID), Product ID (PID) and optionally a serial number.
HID_API_EXPORT hid_device
*HID_API_CALL 
hid_open_path (const char *path)
 Open a HID device by its path name.
int HID_API_EXPORT HID_API_CALL hid_write (hid_device *device, const unsigned char *data, size_t length)
 Write an Output report to a HID device.
int HID_API_EXPORT HID_API_CALL hid_read_timeout (hid_device *dev, unsigned char *data, size_t length, int milliseconds)
 Read an Input report from a HID device with timeout.
int HID_API_EXPORT HID_API_CALL hid_read (hid_device *device, unsigned char *data, size_t length)
 Read an Input report from a HID device.
int HID_API_EXPORT HID_API_CALL hid_set_nonblocking (hid_device *device, int nonblock)
 Set the device handle to be non-blocking.
int HID_API_EXPORT HID_API_CALL hid_send_feature_report (hid_device *device, const unsigned char *data, size_t length)
 Send a Feature report to the device.
int HID_API_EXPORT HID_API_CALL hid_get_feature_report (hid_device *device, unsigned char *data, size_t length)
 Get a feature report from a HID device.
void HID_API_EXPORT HID_API_CALL hid_close (hid_device *device)
 Close a HID device.
int HID_API_EXPORT_CALL hid_get_manufacturer_string (hid_device *device, wchar_t *string, size_t maxlen)
 Get The Manufacturer String from a HID device.
int HID_API_EXPORT_CALL hid_get_product_string (hid_device *device, wchar_t *string, size_t maxlen)
 Get The Product String from a HID device.
int HID_API_EXPORT_CALL hid_get_serial_number_string (hid_device *device, wchar_t *string, size_t maxlen)
 Get The Serial Number String from a HID device.
int HID_API_EXPORT_CALL hid_get_indexed_string (hid_device *device, int string_index, wchar_t *string, size_t maxlen)
 Get a string from a HID device, based on its string index.
HID_API_EXPORT const wchar_t
*HID_API_CALL 
hid_error (hid_device *device)
 Get a string describing the last error which occurred.

Function Documentation

void HID_API_EXPORT HID_API_CALL hid_close ( hid_device device )

Close a HID device.

Parameters:
deviceA device handle returned from hid_open().
struct hid_device_info HID_API_EXPORT* HID_API_CALL hid_enumerate ( unsigned short  vendor_id,
unsigned short  product_id 
) [read]

Enumerate the HID Devices.

This function returns a linked list of all the HID devices attached to the system which match vendor_id and product_id. If vendor_id is set to 0 then any vendor matches. If product_id is set to 0 then any product matches. If vendor_id and product_id are both set to 0, then all HID devices will be returned.

Parameters:
vendor_idThe Vendor ID (VID) of the types of device to open.
product_idThe Product ID (PID) of the types of device to open.
Returns:
This function returns a pointer to a linked list of type struct hid_device, containing information about the HID devices attached to the system, or NULL in the case of failure. Free this linked list by calling hid_free_enumeration().
HID_API_EXPORT const wchar_t* HID_API_CALL hid_error ( hid_device device )

Get a string describing the last error which occurred.

Parameters:
deviceA device handle returned from hid_open().
Returns:
This function returns a string containing the last error which occurred or NULL if none has occurred.
int HID_API_EXPORT HID_API_CALL hid_exit ( void   )

Finalize the HIDAPI library.

This function frees all of the static data associated with HIDAPI. It should be called at the end of execution to avoid memory leaks.

Returns:
This function returns 0 on success and -1 on error.
void HID_API_EXPORT HID_API_CALL hid_free_enumeration ( struct hid_device_info devs )

Free an enumeration Linked List.

This function frees a linked list created by hid_enumerate().

Parameters:
devsPointer to a list of struct_device returned from hid_enumerate().
int HID_API_EXPORT HID_API_CALL hid_get_feature_report ( hid_device device,
unsigned char *  data,
size_t  length 
)

Get a feature report from a HID device.

Set the first byte of data[] to the Report ID of the report to be read. Make sure to allow space for this extra byte in data[]. Upon return, the first byte will still contain the Report ID, and the report data will start in data[1].

Parameters:
deviceA device handle returned from hid_open().
dataA buffer to put the read data into, including the Report ID. Set the first byte of data[] to the Report ID of the report to be read, or set it to zero if your device does not use numbered reports.
lengthThe number of bytes to read, including an extra byte for the report ID. The buffer can be longer than the actual report.
Returns:
This function returns the number of bytes read plus one for the report ID (which is still in the first byte), or -1 on error.
int HID_API_EXPORT_CALL hid_get_indexed_string ( hid_device device,
int  string_index,
wchar_t *  string,
size_t  maxlen 
)

Get a string from a HID device, based on its string index.

Parameters:
deviceA device handle returned from hid_open().
string_indexThe index of the string to get.
stringA wide string buffer to put the data into.
maxlenThe length of the buffer in multiples of wchar_t.
Returns:
This function returns 0 on success and -1 on error.
int HID_API_EXPORT_CALL hid_get_manufacturer_string ( hid_device device,
wchar_t *  string,
size_t  maxlen 
)

Get The Manufacturer String from a HID device.

Parameters:
deviceA device handle returned from hid_open().
stringA wide string buffer to put the data into.
maxlenThe length of the buffer in multiples of wchar_t.
Returns:
This function returns 0 on success and -1 on error.
int HID_API_EXPORT_CALL hid_get_product_string ( hid_device device,
wchar_t *  string,
size_t  maxlen 
)

Get The Product String from a HID device.

Parameters:
deviceA device handle returned from hid_open().
stringA wide string buffer to put the data into.
maxlenThe length of the buffer in multiples of wchar_t.
Returns:
This function returns 0 on success and -1 on error.
int HID_API_EXPORT_CALL hid_get_serial_number_string ( hid_device device,
wchar_t *  string,
size_t  maxlen 
)

Get The Serial Number String from a HID device.

Parameters:
deviceA device handle returned from hid_open().
stringA wide string buffer to put the data into.
maxlenThe length of the buffer in multiples of wchar_t.
Returns:
This function returns 0 on success and -1 on error.
int HID_API_EXPORT HID_API_CALL hid_init ( void   )

Initialize the HIDAPI library.

This function initializes the HIDAPI library. Calling it is not strictly necessary, as it will be called automatically by hid_enumerate() and any of the hid_open_*() functions if it is needed. This function should be called at the beginning of execution however, if there is a chance of HIDAPI handles being opened by different threads simultaneously.

Returns:
This function returns 0 on success and -1 on error.
HID_API_EXPORT hid_device* HID_API_CALL hid_open ( unsigned short  vendor_id,
unsigned short  product_id,
const wchar_t *  serial_number 
)

Open a HID device using a Vendor ID (VID), Product ID (PID) and optionally a serial number.

If serial_number is NULL, the first device with the specified VID and PID is opened.

Parameters:
vendor_idThe Vendor ID (VID) of the device to open.
product_idThe Product ID (PID) of the device to open.
serial_numberThe Serial Number of the device to open (Optionally NULL).
Returns:
This function returns a pointer to a hid_device object on success or NULL on failure.
HID_API_EXPORT hid_device* HID_API_CALL hid_open_path ( const char *  path )

Open a HID device by its path name.

The path name be determined by calling hid_enumerate(), or a platform-specific path name can be used (eg: /dev/hidraw0 on Linux).

Parameters:
pathThe path name of the device to open
Returns:
This function returns a pointer to a hid_device object on success or NULL on failure.
int HID_API_EXPORT HID_API_CALL hid_read ( hid_device device,
unsigned char *  data,
size_t  length 
)

Read an Input report from a HID device.

Input reports are returned to the host through the INTERRUPT IN endpoint. The first byte will contain the Report number if the device uses numbered reports.

Parameters:
deviceA device handle returned from hid_open().
dataA buffer to put the read data into.
lengthThe number of bytes to read. For devices with multiple reports, make sure to read an extra byte for the report number.
Returns:
This function returns the actual number of bytes read and -1 on error. If no packet was available to be read and the handle is in non-blocking mode, this function returns 0.
int HID_API_EXPORT HID_API_CALL hid_read_timeout ( hid_device dev,
unsigned char *  data,
size_t  length,
int  milliseconds 
)

Read an Input report from a HID device with timeout.

Input reports are returned to the host through the INTERRUPT IN endpoint. The first byte will contain the Report number if the device uses numbered reports.

Parameters:
deviceA device handle returned from hid_open().
dataA buffer to put the read data into.
lengthThe number of bytes to read. For devices with multiple reports, make sure to read an extra byte for the report number.
millisecondstimeout in milliseconds or -1 for blocking wait.
Returns:
This function returns the actual number of bytes read and -1 on error. If no packet was available to be read within the timeout period, this function returns 0.
int HID_API_EXPORT HID_API_CALL hid_send_feature_report ( hid_device device,
const unsigned char *  data,
size_t  length 
)

Send a Feature report to the device.

Feature reports are sent over the Control endpoint as a Set_Report transfer. The first byte of data[] must contain the Report ID. For devices which only support a single report, this must be set to 0x0. The remaining bytes contain the report data. Since the Report ID is mandatory, calls to hid_send_feature_report() will always contain one more byte than the report contains. For example, if a hid report is 16 bytes long, 17 bytes must be passed to hid_send_feature_report(): the Report ID (or 0x0, for devices which do not use numbered reports), followed by the report data (16 bytes). In this example, the length passed in would be 17.

Parameters:
deviceA device handle returned from hid_open().
dataThe data to send, including the report number as the first byte.
lengthThe length in bytes of the data to send, including the report number.
Returns:
This function returns the actual number of bytes written and -1 on error.
int HID_API_EXPORT HID_API_CALL hid_set_nonblocking ( hid_device device,
int  nonblock 
)

Set the device handle to be non-blocking.

In non-blocking mode calls to hid_read() will return immediately with a value of 0 if there is no data to be read. In blocking mode, hid_read() will wait (block) until there is data to read before returning.

Nonblocking can be turned on and off at any time.

Parameters:
deviceA device handle returned from hid_open().
nonblockenable or not the nonblocking reads

  • 1 to enable nonblocking
  • 0 to disable nonblocking.
Returns:
This function returns 0 on success and -1 on error.
int HID_API_EXPORT HID_API_CALL hid_write ( hid_device device,
const unsigned char *  data,
size_t  length 
)

Write an Output report to a HID device.

The first byte of data[] must contain the Report ID. For devices which only support a single report, this must be set to 0x0. The remaining bytes contain the report data. Since the Report ID is mandatory, calls to hid_write() will always contain one more byte than the report contains. For example, if a hid report is 16 bytes long, 17 bytes must be passed to hid_write(), the Report ID (or 0x0, for devices with a single report), followed by the report data (16 bytes). In this example, the length passed in would be 17.

hid_write() will send the data on the first OUT endpoint, if one exists. If it does not, it will send the data through the Control Endpoint (Endpoint 0).

Parameters:
deviceA device handle returned from hid_open().
dataThe data to send, including the report number as the first byte.
lengthThe length in bytes of the data to send.
Returns:
This function returns the actual number of bytes written and -1 on error.
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