1# HID DDK Development 2 3## When to Use 4 5The HID driver development kit (DDK) is a toolset that helps you develop HID device drivers at the application layer based on the user mode. It provides interfaces for accessing devices from a host, including creating a device, sending events to a device, and destroying a device. 6 7## Constraints 8 9* The open APIs of the HID DDK can be used to develop drivers of non-standard HID peripherals. 10 11* The open APIs of the HID DDK can be used only within the DriverExtensionAbility lifecycle. 12 13* To use the open APIs of the HID DDK, you need to declare the matching ACL permissions in **module.json5**, for example, **ohos.permission.ACCESS_DDK_HID**. 14 15## Available APIs 16 17| Name| Description| 18| -------- | -------- | 19| OH_Hid_CreateDevice(Hid_Device *hidDevice, Hid_EventProperties *hidEventProperties) | Creates a HID device. When the device is no longer needed, use **OH_Hid_DestroyDevice** to destroy it.| 20| OH_Hid_EmitEvent(int32_t deviceId, const Hid_EmitItem items[], uint16_t length) | Sends events to a HID device.| 21| OH_Hid_DestroyDevice(int32_t deviceId) | Destroys a HID device.| 22 23For details about the APIs, see [HID DDK](../reference/apis-driverdevelopment-kit/_hid_ddk.md). 24 25## How to Develop 26 27The following steps you through the development of a HID device driver with the HID DDK. 28 29**Adding the Dynamic Link Library** 30 31Add the following library to **CMakeLists.txt**. 32```txt 33libhid.z.so 34``` 35 36**Including Header Files** 37```c++ 38#include <hid/hid_ddk_api.h> 39#include <hid/hid_ddk_types.h> 40``` 41 421. Create a device. 43 44 Use **OH_Hid_CreateDevice** in **hid_ddk_api.h** to create a HID device. If the operation is successful, **deviceId** (a non-negative number) is returned. If the operation fails, an error code (a negative number) is returned. 45 46 ```c++ 47 // Construct HID device properties. 48 std::vector<Hid_DeviceProp> deviceProp = {HID_PROP_DIRECT}; 49 std::string deviceName = "keyboard" 50 Hid_Device hidDevice = { 51 .deviceName = deviceName.c_str(), 52 .vendorId = 0x6006, 53 .productId = 0x6006, 54 .version = 1, 55 .bustype = 3, 56 .properties = deviceProp.data(), 57 .propLength = (uint16_t)deviceProp.size() 58 }; 59 // Construct the event properties related to the HID device. 60 std::vector<Hid_EventType> eventType = {HID_EV_ABS, HID_EV_KEY, HID_EV_SYN, HID_EV_MSC}; 61 Hid_EventTypeArray eventTypeArray = {.hidEventType = eventType.data(), .length = (uint16_t)eventType.size()}; 62 std::vector<Hid_KeyCode> keyCode = {HID_BTN_TOOL_PEN, HID_BTN_TOOL_RUBBER, HID_BTN_TOUCH, HID_BTN_STYLUS, HID_BTN_RIGHT}; 63 Hid_KeyCodeArray keyCodeArray = {.hidKeyCode = keyCode.data(), .length = (uint16_t)keyCode.size()}; 64 std::vector<Hid_MscEvent> mscEvent = {HID_MSC_SCAN}; 65 Hid_MscEventArray mscEventArray = {.hidMscEvent = mscEvent.data(), .length = (uint16_t)mscEvent.size()}; 66 std::vector<Hid_AbsAxes> absAxes = {HID_ABS_X, HID_ABS_Y, HID_ABS_PRESSURE}; 67 Hid_AbsAxesArray absAxesArray = {.hidAbsAxes = absAxes.data(), .length = (uint16_t)absAxes.size()}; 68 Hid_EventProperties hidEventProp = { 69 .hidEventTypes = eventTypeArray, 70 .hidKeys = keyCodeArray, 71 .hidAbs = absAxesArray, 72 .hidMiscellaneous = mscEventArray 73 }; 74 // Create a device. The device ID of the device created is returned. 75 int32_t deviceId = OH_Hid_CreateDevice(&hidDevice, &hidEventProp); 76 ``` 77 782. Send an event to a HID device. 79 80 Use **OH_Hid_EmitEvent** of **hid_ddk_api.h** to send an event to the device with the specified **deviceId**. 81 82 ```c++ 83 // Construct the event to be sent. 84 Hid_EmitItem event = {.type = HID_EV_MSC, .code = HID_MSC_SCAN, .value = 0x000d0042}; 85 std::vector<Hid_EmitItem> itemVec; 86 itemVec.push_back(event); 87 // Send the event to a HID device. 88 int32_t ret = OH_Hid_EmitEvent(deviceId, itemVec.data(), (uint16_t)itemVec.size()); 89 ``` 90 913. Release resources. 92 93 Use **OH_Hid_DestroyDevice** of **hid_ddk_api.h** to destroy the device after all requests are processed and before the application exits. 94 95 ```c++ 96 // Destroy a HID device. 97 int32_t ret = OH_Hid_DestroyDevice(deviceId); 98 ``` 99