Detecting DTMF Tones with MATLAB Function
Introduction to DTMF Detection
Steps to Detect DTMF Tones
1. Define the Function: Begin by defining the MATLAB function "DTMFDetector" with x, N, sampleRate, and duration as inputs.
2. Calculate Number of Samples: Determine the total number of samples, "numSamples," using the sampleRate and duration parameters.
3. Create Empty Vector: Initialize an empty vector, "number," to store the detected digits and characters.
4. Iterate Over Signal: Use a for loop to iterate over the input signal, x, in blocks of length N.
5. Apply Discrete Fourier Transform (DFT): Utilize the "fft" function to apply the DFT to each block of the signal.
6. Compute Magnitude Squared: Calculate the squared magnitude of the DFT coefficients, |X[k]|^2, using abs() and ^2 operations.
7. Identify Maximum Magnitude: Determine the maximum magnitude squared value for each DTMF tone frequency (697 Hz, 770 Hz, 852 Hz, 941 Hz, 1209 Hz, 1336 Hz, 1477 Hz).
8. Determine Detected Tone: Based on the identified tone frequencies, determine the corresponding digit or character.
9. Append Detected Digit: Add the detected digit or character to the "number" vector.
10. Return Output: Finally, return the "number" vector as the output of the function.