The idea underlying the realization of the project is the attempt to create an analog to digital front-end device able to acquire an analog signal from the external environment and to sample it in order to have the information in a format suitable for following treatments and elaborations. Specifically the case of study concerns the acquisition of a biological signal and in particular of a signal generated by the human body like the electrocardiographic one. This represents the electric activity (as a cause of the mechanical activity we can easily be aware of) of the heart, that is, the waves of polarization and depolarization involving the myocardial cells that can be detected by some electrodes put on appropriate places of the body surface. It turns out that the first stage of the work which anyway goes over the requirements and the aims of the project should be the correct acquisition of this signal through specific analog equipment like an ECG device able to “extract” the signal and to present it after an early analog filtering and amplification. Leaving the inner problems of this first stage aside, the front-end whose core is the ATmega16 microcontroller, thanks to its internal AD converter, samples the signal and produces a digital one. The sampling rate chosen is 500 Hz, enough to have an optimal band of the signal of circa 250 Hz (indeed this is only an ideal limit to prevent aliasing, the real value should be circa 200 Hz). The microcontroller is programmed through a firmware written in C code in order to handle this signal and extract some information from it, like for example the heart frequency, which is visualized through an LCD display. The information is also sent to a second processing station, like for example a PC which can exploit its larger computing power to storage or to further elaborate the signal and highlight some other features by implementing different algorithms of the signal processing theory.

Download Full Report