HID DDK Development
When to Use
The 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.
Available APIs
Name | Description |
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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. |
OH_Hid_EmitEvent(int32_t deviceId, const Hid_EmitItem items[], uint16_t length) | Sends events to a HID device. |
OH_Hid_DestroyDevice(int32_t deviceId) | Destroys a HID device. |
For details about the APIs, see HID DDK.
How to Develop
The following steps you through the development of a HID device driver with the HID DDK.
Adding the Dynamic Link Library
Add the following library to CMakeLists.txt.
libhid.z.so
Including Header Files
#include <hid/hid_ddk_api.h>
#include <hid/hid_ddk_types.h>
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Create a device.
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.// Construct HID device properties. std::vector<Hid_DeviceProp> deviceProp = {HID_PROP_DIRECT}; std::string deviceName = "keyboard" Hid_Device hidDevice = { .deviceName = deviceName.c_str(), .vendorId = 0x6006, .productId = 0x6006, .version = 1, .bustype = 3, .properties = deviceProp.data(), .propLength = (uint16_t)deviceProp.size() }; // Construct the event properties related to the HID device. std::vector<Hid_EventType> eventType = {HID_EV_ABS, HID_EV_KEY, HID_EV_SYN, HID_EV_MSC}; Hid_EventTypeArray eventTypeArray = {.hidEventType = eventType.data(), .length = (uint16_t)eventType.size()}; std::vector<Hid_KeyCode> keyCode = {HID_BTN_TOOL_PEN, HID_BTN_TOOL_RUBBER, HID_BTN_TOUCH, HID_BTN_STYLUS, HID_BTN_RIGHT}; Hid_KeyCodeArray keyCodeArray = {.hidKeyCode = keyCode.data(), .length = (uint16_t)keyCode.size()}; std::vector<Hid_MscEvent> mscEvent = {HID_MSC_SCAN}; Hid_MscEventArray mscEventArray = {.hidMscEvent = mscEvent.data(), .length = (uint16_t)mscEvent.size()}; std::vector<Hid_AbsAxes> absAxes = {HID_ABS_X, HID_ABS_Y, HID_ABS_PRESSURE}; Hid_AbsAxesArray absAxesArray = {.hidAbsAxes = absAxes.data(), .length = (uint16_t)absAxes.size()}; Hid_EventProperties hidEventProp = { .hidEventTypes = eventTypeArray, .hidKeys = keyCodeArray, .hidAbs = absAxesArray, .hidMiscellaneous = mscEventArray }; // Create a device. The device ID of the device created is returned. int32_t deviceId = OH_Hid_CreateDevice(&hidDevice, &hidEventProp);
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Send an event to a HID device.
Use OH_Hid_EmitEvent of hid_ddk_api.h to send an event to the device with the specified deviceId.// Construct the event to be sent. Hid_EmitItem event = {.type = HID_EV_MSC, .code = HID_MSC_SCAN, .value = 0x000d0042}; std::vector<Hid_EmitItem> itemVec; itemVec.push_back(event); // Send the event to a HID device. int32_t ret = OH_Hid_EmitEvent(deviceId, itemVec.data(), (uint16_t)itemVec.size());
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Release resources.
Use OH_Hid_DestroyDevice of hid_ddk_api.h to destroy the device after all requests are processed and before the application exits.// Destroy a HID device. int32_t ret = OH_Hid_DestroyDevice(deviceId);