INT32S DRV_CounterFreqStart ( PTR_T DeviceHandle， PT_CounterFreqStart *lpCounterFreqStart );
On the device indicated by the DeviceHandle, it configures the specified counter for a frequency measurement and starts the operation.
Some parameters, such as target counter channel (counter), gate period (GatePeriod) and gate mode (GateMode), are stored in the PT_CounterFreqStart structure pointed by the lpCounterFreqStart.
| Name | Direction | Range | Description |
| DeviceHandle | input | default | The pointer retrieved from DRV_DeviceOpen which specifies the target device. |
| lpCounterFreqStart | input / output | default | The pointer to indicate the user-prepared structure PT_CounterFreqStart that stores target counter channel (INT16U counter), gate period (INT16U GatePeriod) and gate mode (INT16U GateMode). |
| 1. 0 | Successful. |
| 2. InvalidDeviceHandle | The Devicehandle is NULL. |
| 3. InvalidChannel | The target channel is out of range. |
| 4. Other value | Please reference ErrorCodes. |