Development Of Piano Tuning Instrument Based On DSP

A new method of the implementation in piano tuning instrument design is presented in this thesis. A piano tuning instrument with small size, convenient manipulation and low price is developed combined with digital signal processing, electronic technology and CAD. In this system the sound of the piano is converted into digital signal from analog through ADC, and the basic frequency can be obtained by using digital signal processing method which separated the sound frequencies and removed the harmonic components in the sound frequencies. After measuring the cycle of the basic frequency signal, the result can be calculated. Meanwhile, the LCD panel also can inform the user the difference between the standard frequency and the measured frequency, so the tension force of the piano string can be adjusted, and the piano tuning can be carried out.The hardware platform, software system, experiment method and the errors analysis are introduced in this thesis. TMS320LF2407A DSP of TI Corporation works as the kernel part of the hardware platform, and the front-end amplifier circuit, the clock and power circuit, JTAG simulator interface circuit, memory extension circuit, LCD display part are also designed, the implemented hardware circuit board provides the platform for the software system. The software works in the CCS environment and the programs include several parts: data acquisition program which converted analog signals into digital signals, digital signal frequency crude measurement by FFT, signal filtering processing, thus implementing the separation of basic frequency and the harmonic components, signal frequency measurement, experiment result display and the standard frequency display. The design ideas and the implementations of each part of the programs are discussed in details. The experiment includes the simulation in MATLAB and the data acquisition of standard signal generation, thus proved the correctness of the algorithm and valued the accuracy of the system. The errors analysis focuses on the analog circuit discussion and digital calculation and then improved that the system maked it.The digital signal processing method designed for the piano tuning instrument in this thesis can measure the basic frequency of the piano string with high accuracy, and provide an objective evidence for piano tuner, it also presents a new way for the piano tuner design in the future.