A method of implementing a digital filter in an event driven engine controller configured to sample an analog signal at a sample rate dependent on a time interval between engine events such as the time interval between pulses from a crank sensor signal. Since the sample rate is variable, the filter coefficients in the digital filter need to be adjusted or updated in response to changes in the sample so that the filter characteristic or transfer function remains consistent even though the sample rate varies.
STATEMENT REGARDING GOVERNMENT SPONSORED DEVELOPMENT
 This invention was made with United States Government support under Government Contract/Purchase Order Number SUB-DE-EE0003347-2 awarded by the Department of Energy. The Government has certain rights in this invention.