Signals and Systems of 3 Familiar Devices
Signals and systems are operating in all the major peripherals of the MP3 player — even in the processor.
In reality, signals are in every part of the system, but pure digital signals are excluded in this example, so memory is not addressed. The processor runs an operating system (OS); under that OS, tasks perform digital signal processing (DSP) algorithms for streaming audio and image data.
All the peripheral blocks (the blocks that sit outside the processor block) contain a combination of continuous- and discrete-time systems. You stream digital music in real time from memory in a compressed format. The processor has to decompress the audio stream into signal sample values (a discrete-time signal) to send to the audio codec. The audio codec contains a digital-to-analog converter (DAC) that converts the discrete-time signal to a continuous-time signal.
The Wi-Fi and Bluetooth radios (blocks with antennas) interface to the processor with digital data but interface to the antenna by using a continuous-time signal at a frequency of 2.4 GHz. The sensors’ block acquires analog signals from the environment, temperature, light level, and acceleration in three dimensions.