There is provided a system architecture including a PPG hardware module and a MEMS hardware module. The PPG hardware module processes PPG raw data, which is generally composed of analog signals or digital signals. The PPG hardware module filters the raw data for later digital calculation to, for example, find out frequency signals with higher peak values. The PPG hardware module then outputs the selected frequency signals to an MCU for heart rate calculation. The MEMS hardware module receives MEMS raw data from a motion detector made of MEMS elements. The MEMS raw data represents motion status of a user that could possibly affect the heart rate determination result. The MEMS hardware module filters the raw data for later digital calculation to find out frequency signals with higher peak values caused by motion.