INT32S DRV_CounterFreqRead ( PTR_T DeviceHandle, PT_CounterFreqRead *lpCounterFreqRead );
On the device indicated by the DeviceHandle, it retrieves the current frequency without disturbing the counting process.
Some parameters, such as target counter channel (counter) and read back frequency (freq), are stored in the PT_CounterFreqRead structure pointed by the lpCounterFreqRead.
| Name | Direction | Range | Description |
| DeviceHandle | input | default | The pointer retrieved from DRV_DeviceOpen which specifies the target device. |
| lpCounterFreqRead | input / output | default | The pointer to indicate the user-prepared structure PT_CounterFreqRead that stores target counter channel (INT16U counter) and pointer to current frequency (FP32 * freq). |
| 1. 0 | Successful. |
| 2. InvalidDeviceHandle | The Devicehandle is NULL. |
| 3. InvalidChannel | The target channel (counter of lpCounterFreqRead ) is out of range. |
| 4. FreqMeasurementFailed | The system timer stops, or the time interval between the latest two function calls is too tight, so that the frequency cannot be properly calculated. |
| 5. Other value | Please reference ErrorCodes |