ECE 3551 Microcomputer Systems 1 Final Project Morse Code Reader Instructor: Dr. Veton Kepuska Term: Fall 2006 By: Erik Lindman & Rong Li

The Goal Of the Project User enter Morse code letters using three PF buttons on the board According to the input, the board plays back the corresponding letter

Problems To Be Solved Convert the recorded audio file into data that can be included into the code Design a proper user interface and interpretation logic Regenerate the voice from the board

Initial Approach The recorded wave file is interpreted using Matlab and covered into a series of coefficients By employing several data organizing methods, the coefficients are stored in a.h file as an array declaration

Initial Approach cont. The LED lights are used to assist the users’ code input and display the result in light pattern Intended to use Timer interrupt to regenerate the voice, by calculating the time interval between samples and increment the coefficient array index accordingly

Major Difficulty The coefficient arrays generated are enormous compare to the board’s memory, as one single letter would have 3.5k coefficients and the board could not load even one of such arrays. The sample rate of the recorder, on the other hand, can not be changed The idea of using Timer interrupt doesn’t work as it is the SPORT interrupt that had the control on the board’s sampling rate. A way needs to be found so we can adjust the sampling rate in our favor

Solution In order to reduce the array size, we drop as many samples as we could, taking only every Nth sample. After multiple tests, we decide that N=10 is the highest we can do while maintaining a recognizable voice pattern. However, even after reducing around 90% of the samples, we could only include letters from A to K

Solution cont. After many different attempts and research, we still could not find a direct way to change the sampling rate of the SPORT interrupt, so we came up with a indirect approach:  ratio++;  if (ratio>39)  ratio=0;  if (ratio%20==0 && index <1000)  index++;

Error Prevention To prevent invalid inputs, the code is made so that the board only takes five values, and if the full Morse code table could be loaded into the board, then there will not be a invalid input. Since there is a corresponding letter/number for each combination of the inputs.

Credit Erik Lindman (50%):  Voice coefficient generation and compression  Importing technique for sampled data into C code  Audio data handling Rong Li (50%):  User interface design  Morse code interpretation  Audio replay techniques

Acknowledgement Special THANKS to :  Dr. Kepuska, for his lecture and constant support  Mr. Hua, for his ever-present advice Thanks to all the great buddies who spent hours and hours with us in the lab