aLec29_sound - 0.5s 1.0s Figure 8.5 The amplitude of a...

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Introduction to Embedded Microcomputer Systems Lecture 29.1 Jonathan W. Valvano . Recap Design a DAC Experimental method Output a sine wave Overview Use DAC to create sounds What are the fundamental limitations? Precision, Sampling rate, Memory size, Processor calculations Testing Need software to create sounds. Frequency is the pitch Humans can hear from about 25 to 20,000 Hz. Middle A is 440 Hz Other notes on a keyboard are determined o 440 * 2 N/12 o "N" is number of notes up or down from middle A. Middle C is 261.6 Hz. music contains multiple harmonics ms 0.0 1.0 2.0 3.0 4.0 5.0 V -5 -4 -3 -2 -1 0 1 2 3 4 5 23Dec2006 10:18 kHz 0.0 0.5 1.0 1.5 2.0 2.5 3.0 -50 -40 -30 -20 -10 0 10 20 23Dec2006 10:18 period Figure 8.3. A waveform shape that generates a trumpet sound. 330 Hz 523 Hz 0.5s 0.5s 1.0s 330 Hz Figure 8.4. You can control the amplitude, frequency and duration of each note (not drawn to scale). period loudness pitch = 1/period
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Introduction to Embedded Microcomputer Systems Lecture 29.2 Jonathan W. Valvano 330 Hz 330 Hz 523 Hz 0.5s
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Unformatted text preview: 0.5s 1.0s Figure 8.5. The amplitude of a plucked string drops exponentially in time. -2-1 1 2 0.005 0.01 0.015 0.02 Time (sec) Sound Amplitude Figure 8.6. A simple chord mixing the notes C and G. How much memory does it take to store a song 3 minutes Stereo channels 44 kHz 12-bit per channel How many bus cycles does it take to output one value? Fetch data from memory Decompress Filter/amplify/mix/envelop DAC speed How do we test Lab 8? Static testing Complete coverage 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15 Corner testing 0,1,2 13,14,15 Interval 0 4 8 12 Voltmeter in AC mode is measure of noise R M S = ∑ − i i V V n 2 ) ( 1 Dynamic testing Oscilloscope (voltage versus time) Spectrum analyzer (voltage versus frequency) The bottom line DAC and OC interrupts create waveforms DAC and ADC have the same two fundamental limits Sampling rate: signal has 0 to ½ fs Number of bits: Resolution = Range/Precision Static testing versus dynamic testing...
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This note was uploaded on 09/19/2010 for the course E E 16280 taught by Professor Valvano during the Fall '10 term at University of Texas.

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aLec29_sound - 0.5s 1.0s Figure 8.5 The amplitude of a...

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