Experiment 2: C programming using functions.

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Horatio Norman
5 years ago
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1 Instructions Experiment 2: C programming using functions. You are required to design, code, test and document C programs for the calculation of the transfer function below. You must prepare the pseudocode for the program (questions 1 to 7) prior to the laboratory session. Failure to prepare pseudcode before entry to the lab will result in the loss of 2 marks. - Q1 requires pseudocode for the whole program - Q2 requires pseudocode for main() and calcdb() functions only - Q3 requires pseudocode for enter_user_data() - Q4 requires pseudocode for calc_real_part() and main() functions only - Q5 requires pseudocode for the imaginary function and main() only - Q6 requires pseudocode for the phase function and main() function only - Q7 requires pseudocode for the whole program All code written must be fully documented including headers and comments. You may use the various run-time C library subroutines to help you with your designs. Information R Vin C Vout Figure 2.1: Low pass Filter The gain and phase response of a low pass filter can be found with the following equations. Gain: db=20log V out V in Phase: θ=arctan Im Re V out V in = Re 2 Im 2 1 Re= Im= wτ 1 wτ 2 1 wτ 2 where ω = 2πf τ = RC

org Experiment Aim Write code to print out the frequency response of the gain and phase for the low pass filter pictured above.

2 The low pass filter should give the following trends for the gain and the phase with chaning frequency. FREQ (Hz) GAIN (db) PHASE (degrees) Gain at Break Point: Phase at Break Point: -3 db -45 o Experiment Aim Write code to print out the frequency response of the gain and phase for the low pass filter pictured above. Frequency response is how the circuit responds to a constant input source that varies in frequency. For this program, the frequency will change linearly. The printout should be in columns with each column separated by a tab character. The headings of the columns are Frequency, Gain in db, Phase in degrees. The user should be asked to enter the range of frequencies to be swept, and the number of frequency points to be printed out. Each frequency step will be the same size. Full error checking of the data should be performed. In order to produce a program of this complexity we need to break the program into modules. Each module can then be tested separately before being integrated into the program as a whole. To introduce this concept you will find a partially completed program on the hard drive of the computer. This is to be used as a template for your program. 1. Run the program supplied and verify the operation of the magnitude function. To test this, perform a hand calculation and compare it to the computers result. Note all values in your lab book. 2. Expand the main() function and the calc_db() function so that the magnitude is printed out in db. Verify the function's operation and note the values. 3. Change the enter_user_data() function so that it allows input of R, C and a single Frequency value. Make sure that R is positive, C is positive and non-zero, and frequency is positive and non-zero. 4. Expand the calc_real_part() function so that it calculates the real part according to the equation given. Verify the function's operation and note the values in your lab book.

3 5. Write a function to calculate the imaginary part according to the equation given. Verify the function's operation and note the values in your lab book. 6. Write a function to calculate the phase. Verify the function's operation and note the values in your lab book. 7. Change the program so that a range of frequencies are used, with the start frequency, end frequency, and number of frequency points are entered by the user. The printout should be in columns with each column separated by a tab character. The headings of the columns are Frequency, Gain in db, Phase in degrees. Full error checking of the data should be perfonned. The template for experiment 2 can be found on the next page.

4 the preprocessor directives go here #include <stdio.h> #include <stdlib.h> #include <math.h> Company: Author: Changes: Function prototypes go here void enter_user_data(float *, float *) ; float magnitude(float, float) ; float calc_db(float) ; void calc_real_part(void) ; main function goes here int main(void) float re, im ; real and imaginary parts float z ; magnitude get the real and imaginary values enter_user_data(&re, &im) ; calculate the magnitude z = magnitude(re, im) ; output the results printf("real:\t%g\nimaginary:\t%g\nmagnitude:\t%g\n",re,im,z) ; Function: enter_user_data void enter_user_data(float *real, float *imag)

5 float re ; real part float im ; imaginary part prompt the user to enter the real part printf("\nenter the real part") ; scanf("%g",&re) ; prompt the user to enter the imaginary part printf("\nenter the imaginary part") ; scanf("%g",&im) ; set the real and imaginary variables in the calling modules *real = re ; *imag = im ; Function: magnitude float magnitude(float real, float imag) float magn ; the magnitude calculate the magnitude magn = sqrt( (real * real) + (imag * imag) ) ; pass the magnitude to the calling module return(magn) ; Function: float calc_db(float av) float db ; the converted value return(db) ;

6 Function: void calc_real_part(void)

GEARMOTORS AF MOTORS FOR INVERTER C-1

GEARMOTORS AF MOTORS FOR INVERTER C-1 C-1 C-2 C-3 C-4 R R C-5 C-6 C-7 1.47 14.7 584Hz 438Hz 318Hz 270Hz 234Hz 206Hz 167Hz 140Hz 121Hz 100Hz 81.4Hz 68.6Hz 59.4Hz 49.2Hz 40.2Hz 33.7Hz 28.9Hz 24.5Hz 21.2Hz 17.9Hz 15.2Hz 12.8Hz 3.11 4.15 5.70