Starts generation of Pulse Width Modulation (PWM) signal on a pin or channel. To check whether a pin is started, use IOCTL_PWM_PIN_IS_STARTED.

Input buffer

Not used with this operation; set to NULL.

Input buffer length

Not used with this operation; set to zero.

Output buffer

Not used with this operation; set to NULL.

Output buffer length

Not used with this operation; set to zero.


To perform this operation, call the DeviceIoControl function with the following parameters.

   DeviceIoControl( (HANDLE)       hDevice,         // handle to device
                    (DWORD)        IOCTL_PWM_PIN_START, // dwIoControlCode(LPDWORD)      NULL,      // input buffer
                    (DWORD)        0,   // size of input buffer
                    (LPDWORD)      NULL,      // output buffer
                    (DWORD)        0,  // size of output buffer
                    (LPDWORD)      lpBytesReturned, // number of bytes returned
                    (LPOVERLAPPED) lpOverlapped );  // OVERLAPPED structure
Parameters Description
hDevice [in] A handle to the device. To obtain a device handle, call the CreateFile function.
dwIoControlCode [in] The control code for the operation. Use IOCTL_PWM_PIN_START for this operation.
lpInBuffer Not used with this operation; set to NULL.
nInBufferSize [in] Not used with this operation; set to zero
lpOutBuffer [out] Not used with this operation; set to NULL.
nOutBufferSize [in] Not used with this operation; set to zero.
lpBytesReturned [out] LPDWORD

A pointer to a variable that receives the size of the data stored in the output buffer, in bytes.

If the output buffer is too small, the call fails, GetLastError returns ERROR_INSUFFICIENT_BUFFER, and lpBytesReturned is zero.

If lpOverlapped is NULL, lpBytesReturned cannot be NULL. Even when an operation returns no output data and lpOutBuffer is NULL, DeviceIoControl makes use of lpBytesReturned. After such an operation, the value of lpBytesReturned is meaningless.

If lpOverlapped is not NULL, lpBytesReturned can be NULL. If this parameter is not NULL and the operation returns data, lpBytesReturned is meaningless until the overlapped operation has completed. To retrieve the number of bytes returned, call GetOverlappedResult. If the hDevice parameter is associated with an I/O completion port, you can retrieve the number of bytes returned by calling GetQueuedCompletionStatus.

lpOverlapped [in] LPOVERLAPPED

A pointer to an OVERLAPPED structure.

If hDevice was opened without specifying FILE_FLAG_OVERLAPPED, lpOverlapped is ignored.

If hDevice was opened with the FILE_FLAG_OVERLAPPED flag, the operation is performed as an overlapped (asynchronous) operation. In this case, lpOverlapped must point to a valid OVERLAPPED structure that contains a handle to an event object. Otherwise, the function fails in unpredictable ways.

For overlapped operations, DeviceIoControl returns immediately, and the event object is signaled when the operation has been completed. Otherwise, the function does not return until the operation has been completed or an error occurs.


Issuing this IOCTL on a pin or channel that is already started has no effect, but does succeed.


Minimum supported client Windows 10 [desktop apps only]
Minimum supported server Windows Server 2016 [desktop apps only]
Header pwm.h (include Pwm.h)

See also