harmony 鸿蒙USB Serial DDK

2025-06-12
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USB Serial DDK

Overview

USB Serial DDK is a development kit for USB drivers. This module provides USB Serial DDK APIs as well as the enum types and data structs used by them.

Serial port communication is often used in industrial scenarios and some legacy devices, such as card issuers and ID card readers. By using the USB Serial DDK APIs, you can develop extended drivers for non-standard peripherals to implement extended functions for USB serial port devices.

System capability: SystemCapability.Driver.SERIAL.Extension

Since: 18

Summary

File

Name	Description
usb_serial_ddk_api.h	Declares the USB Serial DDK APIs used by the host to access the serial port device. File to include: <serial/usb_serial_ddk_api.h> Library: libusb_serial.z.so
usb_serial_types.h	Provides the enum variables, structures, and macros used in USB Serial DDK APIs. File to include: <serial/usb_serial_types.h> Library: libusb_serial.z.so

Structs

Name	Description
struct  UsbSerial_Params	Defines the USB serial port parameters for the USB Serial DDK.

Types

Name	Description
typedef struct UsbSerial_DeviceHandle UsbSerial_DeviceHandle	Defines the data structures for the USB serial port device (opaque).
typedef struct UsbSerial_Params _attribute_((aligned(8))) UsbSerial_Params	Defines the USB serial port parameters used by the USB Serial DDK.

Enums

Name	Description
UsbSerial_DdkRetCode { USB_SERIAL_DDK_NO_PERM = 201, USB_SERIAL_DDK_INVALID_PARAMETER = 401, USB_SERIAL_DDK_SUCCESS = 31600000, USB_SERIAL_DDK_INVALID_OPERATION = 31600001, USB_SERIAL_DDK_INIT_ERROR = 31600002, USB_SERIAL_DDK_SERVICE_ERROR = 31600003, USB_SERIAL_DDK_MEMORY_ERROR = 31600004, USB_SERIAL_DDK_IO_ERROR = 31600005, USB_SERIAL_DDK_DEVICE_NOT_FOUND = 31600006 }	Defines the return codes used by the USB Serial DDK.
UsbSerial_FlowControl { USB_SERIAL_NO_FLOW_CONTROL = 0, USB_SERIAL_SOFTWARE_FLOW_CONTROL = 1, USB_SERIAL_HARDWARE_FLOW_CONTROL = 2 }	Defines the flow control in the USB Serial DDK.
UsbSerial_Parity { USB_SERIAL_PARITY_NONE = 0, USB_SERIAL_PARITY_ODD = 1, USB_SERIAL_PARITY_EVEN = 2 }	Defines the enums of the parity parameter used by the USB Serial DDK.

Functions

Name	Description
int32_t OH_UsbSerial_Init (void)	Initializes the USB Serial DDK.
int32_t OH_UsbSerial_Release (void)	Releases the USB Serial DDK.
int32_t OH_UsbSerial_Open (uint64_t deviceId, uint8_t interfaceIndex, UsbSerial_DeviceHandle **dev)	Enables the USB serial port device based on the specified deviceId and interfaceIndex.
int32_t OH_UsbSerial_Close (UsbSerial_DeviceHandle *dev)	Disables the USB serial port device.
int32_t OH_UsbSerial_Read (UsbSerial_DeviceHandle dev, uint8_t buff, uint32_t bufferSize, uint32_t *bytesRead)	Reads data from the USB serial port device to the buffer.
int32_t OH_UsbSerial_Write (UsbSerial_DeviceHandle dev, uint8_t buff, uint32_t bufferSize, uint32_t *bytesWritten)	Writes the data in the buffer to the USB serial port device.
int32_t OH_UsbSerial_SetBaudRate (UsbSerial_DeviceHandle *dev, uint32_t baudRate)	Sets the baud rate for a USB serial port device. If the parameters of the USB serial port device are set to the default values (the data bit is 8, the stop bit is 1, and parity is disabled for data transfer), you only need to call this API to set the baud rate.
int32_t OH_UsbSerial_SetParams (UsbSerial_DeviceHandle dev, UsbSerial_Params params)	Sets the parameters of the USB serial port device. If the parameters of the USB serial port device are not set to the default values (the data bit is 8, the stop bit is 1, and parity is disabled for data transfer), you only need to call this API to set the related parameters.
int32_t OH_UsbSerial_SetTimeout (UsbSerial_DeviceHandle *dev, int timeout)	Sets the timeout interval (ms) for reading data reported by a USB serial port device. If this function is not called, the timeout value is 0 by default, indicating that data is returned immediately regardless of whether data is read. If you need to wait for a certain period of time or data must be read, call this API to set the timeout interval.
int32_t OH_UsbSerial_SetFlowControl (UsbSerial_DeviceHandle *dev, UsbSerial_FlowControl flowControl)	Sets flow control parameters. Flow control is used to manage the data transfer rate during communication with the USB serial port device to ensure that the sender does not send data that exceeds the processing capability of the receiver. If flow control is required, call this API to set flow control parameters. If this API is not called, flow control is not performed by default.
int32_t OH_UsbSerial_Flush (UsbSerial_DeviceHandle *dev)	Clears the input and output buffers after the write operation is complete. If a large amount of data is to be transmitted to the USB serial port device, the data may be buffered in the kernel for transmission. If the application closes the file descriptor or exits before the data is completely sent out, some data may be lost. You can call this API to ensure that all data is sent before subsequent operations are performed.
int32_t OH_UsbSerial_FlushInput (UsbSerial_DeviceHandle *dev)	Refreshes the input buffer. The data in the buffer is cleared immediately. During the communication with the USB serial port device, especially in the debugging phase, disordered data packets or other exceptions may occur. You can call this API to clear these exceptions to restore the communication.
int32_t OH_UsbSerial_FlushOutput (UsbSerial_DeviceHandle *dev)	Refreshes the output buffer. The data in the buffer is cleared immediately. During the communication with the USB serial port device, especially in the debugging phase, disordered data packets or other exceptions may occur. You can call this API to clear these exceptions to restore the communication.

Type Description

UsbSerial_DeviceHandle

typedef struct UsbSerial_DeviceHandle UsbSerial_DeviceHandle

Description

Defines the data structures for the USB serial port device (opaque).

Since: 18

UsbSerial_Params

typedef struct UsbSerial_Params \__attribute\__((aligned(8))) UsbSerial_Params

Description

Defines the USB serial port parameters for the USB Serial DDK.

Since: 18

Enum Description

UsbSerial_DdkRetCode

enum UsbSerial_DdkRetCode

Description

Defines the return codes used by the USB Serial DDK.

Since: 18

Value	Description
USB_SERIAL_DDK_NO_PERM	No access permission.
USB_SERIAL_DDK_INVALID_PARAMETER	Invalid parameter.
USB_SERIAL_DDK_SUCCESS	Operation succeeded.
USB_SERIAL_DDK_INVALID_OPERATION	Invalid operation.
USB_SERIAL_DDK_INIT_ERROR	Initialization error.
USB_SERIAL_DDK_SERVICE_ERROR	Service error.
USB_SERIAL_DDK_MEMORY_ERROR	Memory-related errors, such as insufficient memory, memory data replication failure, or memory application fault.
USB_SERIAL_DDK_IO_ERROR	I/O error.
USB_SERIAL_DDK_DEVICE_NOT_FOUND	Device not found.

UsbSerial_FlowControl

enum UsbSerial_FlowControl

Description

Defines the flow control mode for the USB Serial DDK.

Since: 18

Value	Description
USB_SERIAL_NO_FLOW_CONTROL	No flow control.
USB_SERIAL_SOFTWARE_FLOW_CONTROL	Software flow control.
USB_SERIAL_HARDWARE_FLOW_CONTROL	Hardware flow control.

UsbSerial_Parity

enum UsbSerial_Parity

Description

Defines the enums of the parity parameter used by the USB Serial DDK.

Since: 18

Value	Description
USB_SERIAL_PARITY_NONE	No parity.
USB_SERIAL_PARITY_ODD	Odd parity.
USB_SERIAL_PARITY_EVEN	Even parity.

Function Description

OH_UsbSerial_Close()

int32_t OH_UsbSerial_Close (UsbSerial_DeviceHandle * dev)

Description

Disables the USB serial port device.

Since: 18

Parameters

Name	Description
dev	Device handle.

Required Permissions

ohos.permission.ACCESS_DDK_USB_SERIAL

Returns

USB_SERIAL_DDK_SUCCESS: Operation succeeded.
USB_SERIAL_DDK_NO_PERM: Permission verification failed.
USB_SERIAL_DDK_INVALID_PARAMETER: Parameter verification failed. Possible cause: The input dev is a null pointer.
USB_SERIAL_DDK_INIT_ERROR: DDK initialization error.
USB_SERIAL_DDK_SERVICE_ERROR: DDK service communication error.
USB_SERIAL_DDK_IO_ERROR: DDK I/O error.
USB_SERIAL_DDK_INVALID_OPERATION: Invalid operation.

OH_UsbSerial_Flush()

int32_t OH_UsbSerial_Flush (UsbSerial_DeviceHandle * dev)

Description

Clears the input and output buffers after the write operation is complete.

If a large amount of data is to be transmitted to the USB serial port device, the data may be buffered in the kernel for transmission. If the application closes the file descriptor or exits before the data is completely sent out, some data may be lost. You can call this API to ensure that all data is sent before subsequent operations are performed.

Since: 18

Parameters

Name	Description
dev	Device handle.

Required Permissions

ohos.permission.ACCESS_DDK_USB_SERIAL

Returns

USB_SERIAL_DDK_SUCCESS: Operation succeeded.
USB_SERIAL_DDK_NO_PERM: Permission verification failed.
USB_SERIAL_DDK_INVALID_PARAMETER: Parameter verification failed. Possible cause: The input dev is a null pointer.
USB_SERIAL_DDK_INIT_ERROR: DDK initialization error.
USB_SERIAL_DDK_SERVICE_ERROR: DDK service communication error.
USB_SERIAL_DDK_IO_ERROR: DDK I/O error.
USB_SERIAL_DDK_INVALID_OPERATION: Invalid operation.

OH_UsbSerial_FlushInput()

int32_t OH_UsbSerial_FlushInput (UsbSerial_DeviceHandle * dev)

Description

Refreshes the input buffer. The data in the buffer is cleared immediately. During the communication with the USB serial port device, especially in the debugging phase, disordered data packets or other exceptions may occur.

You can call this API to clear these exceptions to restore the communication.

Since: 18

Parameters

Name	Description
dev	Device handle.

Required Permissions

ohos.permission.ACCESS_DDK_USB_SERIAL

Returns

USB_SERIAL_DDK_SUCCESS: Operation succeeded.
USB_SERIAL_DDK_NO_PERM: Permission verification failed.
USB_SERIAL_DDK_INVALID_PARAMETER: Parameter verification failed. Possible cause: The input dev is a null pointer.
USB_SERIAL_DDK_INIT_ERROR: DDK initialization error.
USB_SERIAL_DDK_SERVICE_ERROR: DDK service communication error.
USB_SERIAL_DDK_IO_ERROR: DDK I/O error.
USB_SERIAL_DDK_INVALID_OPERATION: Invalid operation.

OH_UsbSerial_FlushOutput()

int32_t OH_UsbSerial_FlushOutput (UsbSerial_DeviceHandle * dev)

Description

Refreshes the output buffer. The data in the buffer is cleared immediately. During the communication with the USB serial port device, especially in the debugging phase, disordered data packets or other exceptions may occur.

You can call this API to clear these exceptions to restore the communication.

Since: 18

Parameters

Name	Description
dev	Device handle.

Required Permissions

ohos.permission.ACCESS_DDK_USB_SERIAL

Returns

USB_SERIAL_DDK_SUCCESS: Operation succeeded.
USB_SERIAL_DDK_NO_PERM: Permission verification failed.
USB_SERIAL_DDK_INVALID_PARAMETER: Parameter verification failed. Possible cause: The input dev is a null pointer.
USB_SERIAL_DDK_INIT_ERROR: DDK initialization error.
USB_SERIAL_DDK_SERVICE_ERROR: DDK service communication error.
USB_SERIAL_DDK_IO_ERROR: DDK I/O error.
USB_SERIAL_DDK_INVALID_OPERATION: Invalid operation.

OH_UsbSerial_Init()

int32_t OH_UsbSerial_Init (void)

Description

Initializes the USB Serial DDK.

Since: 18

Required Permissions

ohos.permission.ACCESS_DDK_USB_SERIAL

Returns

USB_SERIAL_DDK_SUCCESS: Operation succeeded.
USB_SERIAL_DDK_NO_PERM: Permission verification failed.
USB_SERIAL_DDK_INIT_ERROR: DDK initialization error.

OH_UsbSerial_Open()

int32_t OH_UsbSerial_Open (uint64_t deviceId, uint8_t interfaceIndex, UsbSerial_DeviceHandle ** dev)

Description

Enables the USB serial port device based on the specified deviceId and interfaceIndex.

Since: 18

Parameters

Name	Description
deviceId	Device ID.
interfaceIndex	Interface index, which corresponds to bInterfaceNumber in the USB protocol.
dev	Device handle.

Required Permissions

ohos.permission.ACCESS_DDK_USB_SERIAL

Returns

USB_SERIAL_DDK_SUCCESS: Operation succeeded.
USB_SERIAL_DDK_NO_PERM: Permission verification failed.
USB_SERIAL_DDK_INVALID_PARAMETER: Parameter verification failed. Possible cause: The input dev is a null pointer.
USB_SERIAL_DDK_INIT_ERROR: DDK initialization error.
USB_SERIAL_DDK_SERVICE_ERROR: DDK service communication error.
USB_SERIAL_DDK_MEMORY_ERROR: Insufficient memory.
USB_SERIAL_DDK_IO_ERROR: DDK I/O error.
USB_SERIAL_DDK_DEVICE_NOT_FOUND: Device or interface not found.

OH_UsbSerial_Read()

int32_t OH_UsbSerial_Read (UsbSerial_DeviceHandle * dev, uint8_t * buff, uint32_t bufferSize, uint32_t * bytesRead)

Description

Reads data from the USB serial port device to the buffer.

Since: 18

Parameters

Name	Description
dev	Device handle.
buff	Buffer for storing the data read from the USB serial port device.
bufferSize	Buffer size.
bytesRead	Number of bytes that are actually read. If the block mode is set, the number of bytes that are actually read is returned only when it is equal to the value of bufferSize. For details, see OH_UsbSerial_SetTimeout.

Required Permissions

ohos.permission.ACCESS_DDK_USB_SERIAL

Returns

USB_SERIAL_DDK_SUCCESS: Operation succeeded.
USB_SERIAL_DDK_NO_PERM: Permission verification failed.
USB_SERIAL_DDK_INVALID_PARAMETER: Parameter verification failed. Possible causes: 1. dev is a null pointer. 2. buff is a null pointer. 3. bufferSize is 0. 4. bytesRead is a null pointer.
USB_SERIAL_DDK_INIT_ERROR: DDK initialization error.
USB_SERIAL_DDK_SERVICE_ERROR: DDK service communication error.
USB_SERIAL_DDK_MEMORY_ERROR: Invalid buffer address.
USB_SERIAL_DDK_IO_ERROR: DDK I/O error.
USB_SERIAL_DDK_INVALID_OPERATION: Invalid operation.

OH_UsbSerial_Release()

int32_t OH_UsbSerial_Release (void)

Description

Releases the USB Serial DDK.

Since: 18

Required Permissions

ohos.permission.ACCESS_DDK_USB_SERIAL

Returns

USB_SERIAL_DDK_SUCCESS: Operation succeeded.
USB_SERIAL_DDK_NO_PERM: Permission verification failed.
USB_SERIAL_DDK_INIT_ERROR: DDK initialization error.
USB_SERIAL_DDK_SERVICE_ERROR: DDK service communication error.

OH_UsbSerial_SetBaudRate()

int32_t OH_UsbSerial_SetBaudRate (UsbSerial_DeviceHandle * dev, uint32_t baudRate)

Description

Sets the baud rate for a USB serial port device. If the parameters of the USB serial port device are set to the default values (the data bit is 8, the stop bit is 1, and parity is disabled for data transfer), you only need to call this API to set the baud rate.

Since: 18

Parameters

Name	Description
dev	Device handle.
baudRate	Baud rate of the USB serial port device.

Required Permissions

ohos.permission.ACCESS_DDK_USB_SERIAL

Returns

USB_SERIAL_DDK_SUCCESS: Operation succeeded.
USB_SERIAL_DDK_NO_PERM: Permission verification failed.
USB_SERIAL_DDK_INVALID_PARAMETER: Parameter verification failed. Possible cause: The input dev is a null pointer.
USB_SERIAL_DDK_INIT_ERROR: DDK initialization error.
USB_SERIAL_DDK_SERVICE_ERROR: DDK service communication error.
USB_SERIAL_DDK_IO_ERROR: DDK I/O error.
USB_SERIAL_DDK_INVALID_OPERATION: Invalid operation.

OH_UsbSerial_SetFlowControl()

int32_t OH_UsbSerial_SetFlowControl (UsbSerial_DeviceHandle * dev, UsbSerial_FlowControl flowControl)

Description

Sets flow control parameters. Flow control is used to manage the data transfer rate during communication with the USB serial port device to ensure that the sender does not send data that exceeds the processing capability of the receiver.

If flow control is required, call this API to set flow control parameters. If this API is not called, flow control is not performed by default.

Since: 18

Parameters

Name	Description
dev	Device handle.
flowControl	Flow control mode. For details, see UsbSerial_FlowControl.

Required Permissions

ohos.permission.ACCESS_DDK_USB_SERIAL

Returns

USB_SERIAL_DDK_SUCCESS: Operation succeeded.
USB_SERIAL_DDK_NO_PERM: Permission verification failed.
USB_SERIAL_DDK_INVALID_PARAMETER: Parameter verification failed. Possible cause: The input dev is a null pointer.
USB_SERIAL_DDK_INIT_ERROR: DDK initialization error.
USB_SERIAL_DDK_SERVICE_ERROR: DDK service communication error.
USB_SERIAL_DDK_IO_ERROR: DDK I/O error.
USB_SERIAL_DDK_INVALID_OPERATION: Invalid operation.

OH_UsbSerial_SetParams()

int32_t OH_UsbSerial_SetParams (UsbSerial_DeviceHandle * dev, UsbSerial_Params * params)

Description

Sets the parameters of the USB serial port device. If the parameters of the USB serial port device are not set to the default values (the data bit is 8, the stop bit is 1, and parity is disabled for data transfer), you only need to call this API to set the related parameters.

Since: 18

Parameters

Name	Description
dev	Device handle.
params	USB serial port device parameters. For details, see UsbSerial_Params.

Required Permissions

ohos.permission.ACCESS_DDK_USB_SERIAL

Returns

USB_SERIAL_DDK_SUCCESS: Operation succeeded.
USB_SERIAL_DDK_NO_PERM: Permission verification failed.
USB_SERIAL_DDK_INVALID_PARAMETER: Parameter verification failed. Possible causes: 1. dev is a null pointer. 2. params is a null pointer.
USB_SERIAL_DDK_INIT_ERROR: DDK initialization error.
USB_SERIAL_DDK_SERVICE_ERROR: DDK service communication error.
USB_SERIAL_DDK_IO_ERROR: DDK I/O error.
USB_SERIAL_DDK_INVALID_OPERATION: Invalid operation.

OH_UsbSerial_SetTimeout()

int32_t OH_UsbSerial_SetTimeout (UsbSerial_DeviceHandle * dev, int timeout)

Description

Sets the timeout interval (ms) for reading data reported by a USB serial port device.

If this function is not called, the timeout value is 0 by default, indicating that data is returned immediately regardless of whether data is read. If you need to wait for a certain period of time or data must be read, call this API to set the timeout interval.

Since: 18

Parameters

Name

Description

dev

Device handle.

timeout

Timeout interval for reading data from a USB serial port device. The value range is as follows:
- (0, 25500]: time value in milliseconds. The value is rounded off to the nearest 100 milliseconds as the actual timeout interval. For example, if the value is set to 12321, the effective timeout interval is 12300.
- 0: Data is returned immediately.
- -1: Data is read in block mode. That is, data is returned only after data of the specified length is read. For details, see OH_UsbSerial_Read.

Required Permissions

ohos.permission.ACCESS_DDK_USB_SERIAL

Returns

USB_SERIAL_DDK_SUCCESS: Operation succeeded.
USB_SERIAL_DDK_NO_PERM: Permission verification failed.
USB_SERIAL_DDK_INVALID_PARAMETER: Parameter verification failed. Possible causes: 1. dev is a null pointer. 2. timeout is less than -1 or greater than 25500.
USB_SERIAL_DDK_INIT_ERROR: DDK initialization error.
USB_SERIAL_DDK_SERVICE_ERROR: DDK service communication error.
USB_SERIAL_DDK_IO_ERROR: DDK I/O error.
USB_SERIAL_DDK_INVALID_OPERATION: Invalid operation.

OH_UsbSerial_Write()

int32_t OH_UsbSerial_Write (UsbSerial_DeviceHandle * dev, uint8_t * buff, uint32_t bufferSize, uint32_t * bytesWritten)

Description

Writes the data in the buffer to the USB serial port device.

Since: 18

Parameters

Name	Description
dev	Device handle.
buff	Buffer to which the data of the USB serial port device is written.
bufferSize	Buffer size.
bytesWritten	Number of bytes that are actually written.

Required Permissions

ohos.permission.ACCESS_DDK_USB_SERIAL

Returns

USB_SERIAL_DDK_SUCCESS: Operation succeeded.
USB_SERIAL_DDK_NO_PERM: Permission verification failed.
USB_SERIAL_DDK_INVALID_PARAMETER: Parameter verification failed. Possible causes: 1. dev is a null pointer. 2. buff is a null pointer. 3. bufferSize is 0. 4. bytesWritten is a null pointer.
USB_SERIAL_DDK_INIT_ERROR: DDK initialization error.
USB_SERIAL_DDK_SERVICE_ERROR: DDK service communication error.
USB_SERIAL_DDK_IO_ERROR: DDK I/O error.
USB_SERIAL_DDK_INVALID_OPERATION: Invalid operation.