The system modelling stage, carried out using Simulink, and the Raspberry Pi2 implementation, will be thus followed by a signal measurement phase, aimed at checking the correct functioning of the system.
In order to realize a complete workstation, the items depicted in the figure aside are needed.
As for the measurement instruments, the typical devices usually available in didactic labs for electronics and telecommunications are needed, with particular reference to:
- a signal generator;
- an oscilloscope;
- a spectrum analyser.
It is worth noting that the signals that will be generated/processed by our systems are within the [0 24 kHz] band, owing to the characteristics of the Raspberry Pi’s input and output ports. For the generation or analysis of such signals there is no need for sophisticated instruments; the basic instruments typically available in a didactic lab, generally solid but not highly performing, are suitable for the experimental activities described below.
Nonetheless, even basic oscilloscopes and spectrum analysers are costly devices for students or hobbyists. Apparently, therefore, the experiences here presented cannot be performed at home, where lab instruments are usually not available.
Indeed, this is not true. Recently, low cost, multi-purpose instruments have been conceived for low frequency applications. On this regard the Digilent Analog Discovery device is worth special attention.
When connected to the PC through the USB port, this device is able to generate and acquire signals. With a moderate price, in the order of 270$, this tool can operate as signal generator, oscilloscope, spectrum analyser, network analyser, logic state analyser, digital signal generator and power supply. The user interface of each single instrument, displayed on the PC's monitor, shows the same knobs, sliders and buttons of the full-hardware instrument, allowing the user to perform the measurement activity as in a lab.
Of course, the upper limit of the bandwidth that can be handled by the Digilent Analog Discovery, in the order of some MHz, cannot be compared with that of more sophisticated and expensive instruments, however it is more than adequate for the didactic experiences described below.
In this case, therefore, the signal generator, the oscilloscope and the spectrum analyser can be conveniently replaced by this multifunction tool.
Example of workstation setup