Signal Processing Application - Morse Code

   This was a Group Experiment performed by Aishwarya Bannore, Varad Choudhari, Gauri Joijode, Amisha Khimani and Apoorva Laharia. We choose "Morse Code Generator from a given Analog Signal" as an application.

Problem Definition :
1) Accept Analogy input and convert it into Digital Signal(Binary).
2) Covert Binary to Morse and implement the dots and dashes as 0 and 1 respectively.
    (Dots = 1 = LED ON, Dash = 0 = LED OFF)

Patent Review :International Morse Code Number GeneratorPatent Number :- US4292624
Inventors :- Serp William K.
Publication Date :- 09/29/1981
Application Number :- 05/517813

Summary :- 
Morse code is a code in which letters are represented by combinations of long and short light or sound signals.It transmits text as a series of on-off tones,lights or clicks. The code which is to be transmitted is loaded into preset-able counters.Switch mean is used to connect the  binary level to a specific memory location.The counter thereby sends data sequentially generating Morse Code.It sends one digit at a time.The next lesser significant digit to the address and binary counter are recycled. Switching means are used for the generation of leading zeros and for selectively abbreviating the international Morse code of certain digit comprising the numbers.

Applications:-
It allows physically handicapped person to communicate by the means of tap or blink.
In aviation, pilots use the Morse code to ensure whether the stations are servicable or not by transmitting a short set of identification numbers.

Patent's Link :- International Morse Code Generator

IEEE Paper Review:
Automatic Morse Code recognition with adaptive variable ratio threshold prediciton for physically handicapped persons.Authors :- Ching-Hsing Luo
                 Ming-Che Hsien
Publisher :- IEEE
Published in :- Engineering in Medicine and Biology,1999. 21st annual conference and the 1999 annual fall meeting of biomedical engineering society.
Date of Conference :- 1999

Summary:-
Morse code helps physically impaired persons to communicate easily. However they have difficulties in maintaining a stable type. Hence the threshold and prediction method is in demand. In threshold prediction, the Morse code time series with unit time period and ratio are used.Two least mean square predictors are applied to trace the dash and the dot interval and the dot-dash difference and a predicted threshold based on a variable ratio decision rule is used to distinguish between dashes and dots. The same method is applied to identify the character space.

Paper's Link :- Predictive threshold Morse Code

The link to the IEEE paper on our application and its plagiarism report is mentioned below:-
Plagiarism
Morse Code Generator

DSP processor (TMS320F28375)

This was a demonstration experiment where our seniors showed us how to operate a DSP processor by showing a project. The output of the project was verified with the help of a microphone and the noise present in the output was negligible. Our seniors showed us various instructions and their syntax. We performed arithmetic, logical and shift operations and observed the input and output before and after execution.

Frequency Sampling Method

In this experiment a digital FIR filter is designed using Frequency sampling method.In FSM we subsitute w=2(pi)k/n.5 parameters namely, Attenuation in both pass and stop bands in dB, pass band and stop band frequencies in Hertz and Sampling frequency in Hertz are taken from user. Once we obtain the desired frequency response, Hd[w], we can directly convert them into the frequency domain  using the conventional Discrete Fourier Transform algorithm, H[k]. The final output sequence, h[n] can be obtained by performing the  Inverse Discrete Fourier Transform algorithm. The final output sequence, h[n] is always symmetric about the point of symmetry i.e. N/2 . Discontinuity is observed in phase plot between lobes and also when the spectrum goes out of the range that is from -pi to +pi. 
Link:- FSM

Window Function

In this experiment we used a particular windowing function based upon the attenuation in stop band.There are  different types of windowing functions Rectangular ,Bartlett ,Hamming ,Hanning, and Blackman.The specifications of As,Ap, stop band frequency, passband frequency and sampling frequency are taken from the user.It is observed that as the order of the filter increases the number of lobes in frequency response increase.The attenuation depends upon the type of window used. 
Link:- Window function

Chebyshev IIR filter

The Chebyshev IIR filter was designed in scilab, chebyshev filter contains ripples in pass band and stop band in its magnitude spectrum. The order of the chebyshev filter is equal to the number of ripples .LPF and HPF were designed according to the input specifications and then were compared with the values obtained from the graph. We observed that the number of poles in butterworth filter is more than chebyshev filter.
Link:- Chebyshev

Butterworth Filter

This experiment was done using scilab. In this experiment a digital filter was designed using analog filter. Digital butterworth filter can be designed using two methods impluse invariant method and BLT method. For HPF and LPF,all poles lie in the unit circle.Hence filters are stable. But  the value of Ap in HPF and As in LPF are not completely verified, so we need to increase the order of the filter.
Link:- Butterworth

Overlap add and Overlap save method

Overlap add and Overlap save method are algorithms for decreasing the delay and hence it is used for large input signals.In these methods the decomposed length is specified of the input as well as the output signal.It therefore filters long data sequence and reduces the complication.In OAM zeros are added as per the length of the decomposed signal and is divided into N number of short length signals. In OSM the decomposed signal of the first short length consists of zero, since the second signal consists the first signal as well, it saves the data.

Link:-

OSM

OAM