Chapter 13: Digital to Analog Conversion and Sound

Embedded Systems - Shape The World
Jonathan Valvano and Ramesh Yerraballi

As part of the edX online class, we made some interactive web pages to illustrate fundamental concepts


Interactive web pages: Table of Contents

2. Fundamental Concepts Number conversions
5. Introduction to C Flowcharts, C vs assembly
6. Microcontroller Ports Input/output, direction register
7. Design and Development Successive refinement, if-then, loops
10. Finite State Machines Vending machine and stepper motor
11. UART Serial Interface Blind, busy-wait, interrupt, serial port
12. Interrupts Mail box, context switch
13. DAC and Sound Sampling rate, precision, how a DAC works
14. ADC and Data Acquisition    How an ADC works, Nyquist Theorem

 

Interactive Tool 13.1

Discover the Nyquist Theorem. A Continuous waveform like Figure 13.1 is shown, V = 1.5 + 1*sin(2pi50t)+0.5*cos(2pi 200t). You may select the sampling rate and the precision (in bits) to see the signal captured. Notice that at sampling rates above 100 Hz you capture the essence of the 50Hz periodic wave, and above 400 Hz you capture the essence of both the 50 and 200 Hz waves. To “capture the essence” means the analog and digital signal go up and down at the same rate.

sampling frequency = Hz
Number of ADC bits = bit(s)

 

Interactive Tool 13.2

Learn about DAC precision using this tool. The analog output is fixed in the range 0 to 3.3V. You may adjust the number of bits from 1 to 10 to see how close the fit is to the straight line.

1 10 Number of DAC bits = 0

 

Interactive Tool 13.3

Shows how to compute Vout for the two scenarios bit1=0;bit0=1 and bit1=1;bit0=0. Using superposition, the scenario bit1=1;bit0=1 is simply the sum of the two cases: bit1=0;bit0=1 and bit1=1;bit0=0.

bit 0: bit 1:

 

Reprinted with approval from Embedded Systems: Introduction to ARM Cortex-M Microcontrollers, 2016, ISBN: 978-1477508992, http://users.ece.utexas.edu/~valvano/arm/outline1.htm

and from Embedded Systems: Real-Time Interfacing to ARM® Cortex™-M Microcontrollers, 2016, ISBN: 978-1463590154, http://users.ece.utexas.edu/~valvano/arm/outline.htm

Creative Commons License
Embedded Systems - Shape the World by Jonathan Valvano and Ramesh Yerraballi is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
Based on a work at http://users.ece.utexas.edu/~valvano/arm/outline1.htm.