hidapi
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Macros | Enumerations | Functions
hidapi API

Macros

#define HID_API_VERSION_MAJOR   0
 Static/compile-time major version of the library.
 
#define HID_API_VERSION_MINOR   14
 Static/compile-time minor version of the library.
 
#define HID_API_VERSION_PATCH   0
 Static/compile-time patch version of the library.
 
#define HID_API_MAKE_VERSION(mj, mn, p)   (((mj) << 24) | ((mn) << 8) | (p))
 Coverts a version as Major/Minor/Patch into a number: <8 bit major><16 bit minor><8 bit patch>.
 
#define HID_API_VERSION   HID_API_MAKE_VERSION(HID_API_VERSION_MAJOR, HID_API_VERSION_MINOR, HID_API_VERSION_PATCH)
 Static/compile-time version of the library.
 
#define HID_API_VERSION_STR   HID_API_TO_VERSION_STR(HID_API_VERSION_MAJOR, HID_API_VERSION_MINOR, HID_API_VERSION_PATCH)
 Static/compile-time string version of the library.
 
#define HID_API_MAX_REPORT_DESCRIPTOR_SIZE   4096
 Maximum expected HID Report descriptor size in bytes.
 

Enumerations

enum  hid_bus_type {
  HID_API_BUS_UNKNOWN = 0x00 , HID_API_BUS_USB = 0x01 , HID_API_BUS_BLUETOOTH = 0x02 , HID_API_BUS_I2C = 0x03 ,
  HID_API_BUS_SPI = 0x04
}
 HID underlying bus types. More...
 

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 *dev, 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 *dev, 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 *dev, int nonblock)
 Set the device handle to be non-blocking.
 
int HID_API_EXPORT HID_API_CALL hid_send_feature_report (hid_device *dev, 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 *dev, unsigned char *data, size_t length)
 Get a feature report from a HID device.
 
int HID_API_EXPORT HID_API_CALL hid_send_output_report (hid_device *dev, const unsigned char *data, size_t length)
 Send a Output report to the device.
 
int HID_API_EXPORT HID_API_CALL hid_get_input_report (hid_device *dev, unsigned char *data, size_t length)
 Get a input report from a HID device.
 
void HID_API_EXPORT HID_API_CALL hid_close (hid_device *dev)
 Close a HID device.
 
int HID_API_EXPORT_CALL hid_get_manufacturer_string (hid_device *dev, 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 *dev, 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 *dev, wchar_t *string, size_t maxlen)
 Get The Serial Number String from a HID device.
 
struct hid_device_info HID_API_EXPORT *HID_API_CALL hid_get_device_info (hid_device *dev)
 Get The struct hid_device_info from a HID device.
 
int HID_API_EXPORT_CALL hid_get_indexed_string (hid_device *dev, int string_index, wchar_t *string, size_t maxlen)
 Get a string from a HID device, based on its string index.
 
int HID_API_EXPORT_CALL hid_get_report_descriptor (hid_device *dev, unsigned char *buf, size_t buf_size)
 Get a report descriptor from a HID device.
 
HID_API_EXPORT const wchar_t *HID_API_CALL hid_error (hid_device *dev)
 Get a string describing the last error which occurred.
 
HID_API_EXPORT const struct hid_api_version *HID_API_CALL hid_version (void)
 Get a runtime version of the library.
 
HID_API_EXPORT const char *HID_API_CALL hid_version_str (void)
 Get a runtime version string of the library.
 

Detailed Description

Macro Definition Documentation

◆ HID_API_MAKE_VERSION

#define HID_API_MAKE_VERSION (   mj,
  mn,
 
)    (((mj) << 24) | ((mn) << 8) | (p))

Coverts a version as Major/Minor/Patch into a number: <8 bit major><16 bit minor><8 bit patch>.

This macro was added in version 0.12.0.

Convenient function to be used for compile-time checks, like:

#if HID_API_VERSION >= HID_API_MAKE_VERSION(0, 12, 0)
Examples
test.c.

◆ HID_API_MAX_REPORT_DESCRIPTOR_SIZE

#define HID_API_MAX_REPORT_DESCRIPTOR_SIZE   4096

Maximum expected HID Report descriptor size in bytes.

Since version 0.13.0, HID_API_VERSION >= HID_API_MAKE_VERSION(0, 13, 0)

Examples
test.c.

◆ HID_API_VERSION

Static/compile-time version of the library.

This macro was added in version 0.12.0.

See also
HID_API_MAKE_VERSION.
Examples
test.c.

◆ HID_API_VERSION_MAJOR

#define HID_API_VERSION_MAJOR   0

Static/compile-time major version of the library.

◆ HID_API_VERSION_MINOR

#define HID_API_VERSION_MINOR   14

Static/compile-time minor version of the library.

◆ HID_API_VERSION_PATCH

#define HID_API_VERSION_PATCH   0

Static/compile-time patch version of the library.

◆ HID_API_VERSION_STR

#define HID_API_VERSION_STR   HID_API_TO_VERSION_STR(HID_API_VERSION_MAJOR, HID_API_VERSION_MINOR, HID_API_VERSION_PATCH)

Static/compile-time string version of the library.

Examples
test.c.

Enumeration Type Documentation

◆ hid_bus_type

HID underlying bus types.

Enumerator
HID_API_BUS_UNKNOWN 

Unknown bus type

HID_API_BUS_USB 

USB bus Specifications: https://usb.org/hid

HID_API_BUS_BLUETOOTH 

Bluetooth or Bluetooth LE bus Specifications: https://www.bluetooth.com/specifications/specs/human-interface-device-profile-1-1-1/ https://www.bluetooth.com/specifications/specs/hid-service-1-0/ https://www.bluetooth.com/specifications/specs/hid-over-gatt-profile-1-0/

HID_API_BUS_I2C 

I2C bus Specifications: https://docs.microsoft.com/previous-versions/windows/hardware/design/dn642101(v=vs.85)

HID_API_BUS_SPI 

SPI bus Specifications: https://www.microsoft.com/download/details.aspx?id=103325

Function Documentation

◆ hid_close()

void HID_API_EXPORT HID_API_CALL hid_close ( hid_device dev)

Close a HID device.

Parameters
devA device handle returned from hid_open().
Examples
test.c.

◆ hid_enumerate()

struct hid_device_info HID_API_EXPORT *HID_API_CALL hid_enumerate ( unsigned short  vendor_id,
unsigned short  product_id 
)

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_info, containing information about the HID devices attached to the system, or NULL in the case of failure or if no HID devices present in the system. Call hid_error(NULL) to get the failure reason.
Note
The returned value by this function must to be freed by calling hid_free_enumeration(), when not needed anymore.
Examples
test.c.

◆ hid_error()

HID_API_EXPORT const wchar_t *HID_API_CALL hid_error ( hid_device dev)

Get a string describing the last error which occurred.

This function is intended for logging/debugging purposes.

This function guarantees to never return NULL. If there was no error in the last function call - the returned string clearly indicates that.

Any HIDAPI function that can explicitly indicate an execution failure (e.g. by an error code, or by returning NULL) - may set the error string, to be returned by this function.

Strings returned from hid_error() must not be freed by the user, i.e. owned by HIDAPI library. Device-specific error string may remain allocated at most until hid_close() is called. Global error string may remain allocated at most until hid_exit() is called.

Parameters
devA device handle returned from hid_open(), or NULL to get the last non-device-specific error (e.g. for errors in hid_open() or hid_enumerate()).
Returns
A string describing the last error (if any).
Examples
test.c.

◆ hid_exit()

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.
Examples
test.c.

◆ hid_free_enumeration()

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().
Examples
test.c.

◆ hid_get_device_info()

struct hid_device_info HID_API_EXPORT *HID_API_CALL hid_get_device_info ( hid_device dev)

Get The struct hid_device_info from a HID device.

Since version 0.13.0, HID_API_VERSION >= HID_API_MAKE_VERSION(0, 13, 0)

Parameters
devA device handle returned from hid_open().
Returns
This function returns a pointer to the struct hid_device_info for this hid_device, or NULL in the case of failure. Call hid_error(dev) to get the failure reason. This struct is valid until the device is closed with hid_close().
Note
The returned object is owned by the dev, and SHOULD NOT be freed by the user.
Examples
test.c.

◆ hid_get_feature_report()

int HID_API_EXPORT HID_API_CALL hid_get_feature_report ( hid_device dev,
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
devA 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. Call hid_error(dev) to get the failure reason.
Examples
test.c.

◆ hid_get_indexed_string()

int HID_API_EXPORT_CALL hid_get_indexed_string ( hid_device dev,
int  string_index,
wchar_t *  string,
size_t  maxlen 
)

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

Parameters
devA 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. Call hid_error(dev) to get the failure reason.
Examples
test.c.

◆ hid_get_input_report()

int HID_API_EXPORT HID_API_CALL hid_get_input_report ( hid_device dev,
unsigned char *  data,
size_t  length 
)

Get a input report from a HID device.

Since version 0.10.0, HID_API_VERSION >= HID_API_MAKE_VERSION(0, 10, 0)

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
devA 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. Call hid_error(dev) to get the failure reason.

◆ hid_get_manufacturer_string()

int HID_API_EXPORT_CALL hid_get_manufacturer_string ( hid_device dev,
wchar_t *  string,
size_t  maxlen 
)

Get The Manufacturer String from a HID device.

Parameters
devA 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. Call hid_error(dev) to get the failure reason.
Examples
test.c.

◆ hid_get_product_string()

int HID_API_EXPORT_CALL hid_get_product_string ( hid_device dev,
wchar_t *  string,
size_t  maxlen 
)

Get The Product String from a HID device.

Parameters
devA 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. Call hid_error(dev) to get the failure reason.
Examples
test.c.

◆ hid_get_report_descriptor()

int HID_API_EXPORT_CALL hid_get_report_descriptor ( hid_device dev,
unsigned char *  buf,
size_t  buf_size 
)

Get a report descriptor from a HID device.

Since version 0.14.0, HID_API_VERSION >= HID_API_MAKE_VERSION(0, 14, 0)

User has to provide a preallocated buffer where descriptor will be copied to. The recommended size for preallocated buffer is HID_API_MAX_REPORT_DESCRIPTOR_SIZE bytes.

Parameters
devA device handle returned from hid_open().
bufThe buffer to copy descriptor into.
buf_sizeThe size of the buffer in bytes.
Returns
This function returns non-negative number of bytes actually copied, or -1 on error.
Examples
test.c.

◆ hid_get_serial_number_string()

int HID_API_EXPORT_CALL hid_get_serial_number_string ( hid_device dev,
wchar_t *  string,
size_t  maxlen 
)

Get The Serial Number String from a HID device.

Parameters
devA 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. Call hid_error(dev) to get the failure reason.
Examples
test.c.

◆ hid_init()

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. Call hid_error(NULL) to get the failure reason.
Examples
test.c.

◆ hid_open()

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. Call hid_error(NULL) to get the failure reason.
Note
The returned object must be freed by calling hid_close(), when not needed anymore.
Examples
test.c.

◆ hid_open_path()

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. Call hid_error(NULL) to get the failure reason.
Note
The returned object must be freed by calling hid_close(), when not needed anymore.
Examples
test.c.

◆ hid_read()

int HID_API_EXPORT HID_API_CALL hid_read ( hid_device dev,
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
devA 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. Call hid_error(dev) to get the failure reason. If no packet was available to be read and the handle is in non-blocking mode, this function returns 0.
Examples
test.c.

◆ hid_read_timeout()

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
devA 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. Call hid_error(dev) to get the failure reason. If no packet was available to be read within the timeout period, this function returns 0.

◆ hid_send_feature_report()

int HID_API_EXPORT HID_API_CALL hid_send_feature_report ( hid_device dev,
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
devA 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. Call hid_error(dev) to get the failure reason.
Examples
test.c.

◆ hid_send_output_report()

int HID_API_EXPORT HID_API_CALL hid_send_output_report ( hid_device dev,
const unsigned char *  data,
size_t  length 
)

Send a Output report to the device.

Since version 0.15.0, HID_API_VERSION >= HID_API_MAKE_VERSION(0, 15, 0)

Output 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_output_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_output_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.

This function sets the return value of hid_error().

Parameters
devA 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.
See also
hid_write

◆ hid_set_nonblocking()

int HID_API_EXPORT HID_API_CALL hid_set_nonblocking ( hid_device dev,
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
devA 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. Call hid_error(dev) to get the failure reason.
Examples
test.c.

◆ hid_version()

HID_API_EXPORT const struct hid_api_version *HID_API_CALL hid_version ( void  )

Get a runtime version of the library.

This function is thread-safe.

Returns
Pointer to statically allocated struct, that contains version.
Examples
test.c.

◆ hid_version_str()

HID_API_EXPORT const char *HID_API_CALL hid_version_str ( void  )

Get a runtime version string of the library.

This function is thread-safe.

Returns
Pointer to statically allocated string, that contains version string.
Examples
test.c.

◆ hid_write()

int HID_API_EXPORT HID_API_CALL hid_write ( hid_device dev,
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 interrupt OUT endpoint, if one exists. If it does not the behaviour is as hid_send_output_report

Parameters
devA 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. Call hid_error(dev) to get the failure reason.
Examples
test.c.