The Design And Implementation Of A Digital Oscilloscope Based On The AVR Single Chip Microcomputer

Digital oscilloscope is an electronic instrucment used for observing, measuring,analysing, and recording various dynamic signal and displaying graphically therelationship between the various dynamic and time. On the market the price ofoscilloscope is generally expensive, so a design scheme of low cost digitaloscilloscope is put forward.The main content of this thesis is divided into two parts:the design of hardwareand software for the digital oscilloscope. The hardware contains the circuits ofprocessing signal, sampling, FIFO buffer memory, DDS clock, TFT displays andthe keys. The design of system software includes controlling and driving thedevices of microcontroller peripheral circuit, as well as analysising and processingthe datas of the collected waveform.The AVR single microcomputer of the company of ATMEL is used as thecontrol core in this digital oscilloscope, the AVR single microcomputer is areduced instruction set computer, it is many times faster than the conventionalcomplex instruction set computer in term of instructions and data thoughput. In thecircuits of Signal Conditioning, a structure is applied consist of a variable gainoperational amplifier and a high precision DAC. The magnification is controlled bythe voltage from the DAC output. This structure can reduce the power of the circuit,also, the magnification can be adjusted to that we require by the software, whichwould be more convinent for us to control. The converter of ADS830E is applied inthe sampling circuit, the maximum frequency of the ADS830E is achieved to60MHZ,that is far higher than the operating frequency of the microcontroller, while,the operating frequency of general oscilloscope CPU is higner than the operatingfrequency of AD converter, in order to keep the same speed with the AD converter,the high-speed FIFO buffer memory is joined behind the AD converter. DDS circuitis used for creating clock signals for the AD converter, DDS is direct digitalfrequency synthesizer. The circuit of DDS is simple without external components. The output of frequency and phase are controlled by the program and is easy toadjust, however,the multi-level gate is applied to master clock oscillator intraditional oscilloscope for the sampling clock that required.its circuit is not onlycomplex structure but also power consumption. Compared with gate divider,DDS isvantaggio.Finally the digital oscilloscope operates normally, its bandwidth is1MHz andits input signal range is5mVto160V.And it can be used for sampling, displayingwaveform, measuring the parameters of frequency and peak, and FFT spectrumanalysis.