Returns the imp’s effective sample rate
Only available on the imp004m (impOS 38+) and imp006 (impOS 42+)
Float — the dfsdm sample rate in Hertz
This method calculates the effective sample rate of the dfsdm from the filter parameters and the time taken to obtain the most recent sample. If no samples have yet been obtained, the method will return 0, so to obtain a meaningful value from this method, dfsdm must have been both configured, started and at least one sample collected.