When you are working on an embedded system and sampling data from a sensor, sometimes you just need a quick and simple low-pass filter to smooth out a noisy signal or a high-pass filter to remove a (perhaps slightly varying) DC offset. If you are not particularly concerned about the exact characteristics of the filter response (such as cutoff frequency, stop-band attenuation, pass-band ripple, etc.) but just need something that is halfway decent and can be implemented quickly, then you might find the following two filters interesting.