Essentially, the Magic Morse algorithm assigns a weight to dits and dahs as the stream is received. When a word space or longer is encountered, the algorithm instantly has a calculated pointer into an array stored in eeprom and the decoded character is returned. Magic Morse is a copyrighted algorithm but the Arduino code is Open Source and it is hoped you have lots of fun with this implementation.
The algorithm will generate a number between 1 and 255 for every Morse Code combination decoded. For every DAH identified in the stream, a binary weight is applied based upon the position of the DAH... that is, first, second, third, fourth, or fifth element. DITs are not weighted but are counted with DAHs to achieve a total element count of DITs + DAHs in the character. The DAH-weights are bits 3-7 in a calculated index and the elements number make up bits 0-2.
E = "DIT" Therefore, there are no DAHs and only one element. The pointer is %00000001 Index = 1
F = "DIT DIT DAH DIT" and the DAH is in the third position (bit 5 set) Pointer = %00100100 Index = 36
Readers wishing to learn more about the algorithm implementation can refer to:
// defines associated specifically with Nokia 5110 LCD ScrnFuncts #define PIN_SCE 7 #define PIN_RESET 6 #define PIN_DC 5 #define PIN_SDIN 4 #define PIN_SCLK 3 #define LCD_C LOW #define LCD_D HIGH #define LCD_X 84 #define LCD_Y 48 /* ************************************************ Notes & Changes*********************************************** CHANGES: 20130515: Minor change moving functions between modules, created UtilFuncts.ino Implemented Verbose Pin#9 Tightened setspeed() values and added console echo during verbose 20130512: Combined separate IF logic into more complex single statement in MagicMorse decode 20130510: Corrected maximum Elements to scan to correct Prosigns. Added MaxElement constant 20130508: Implemented LCDCurrentLine() to identify the current LCD active line Implemented PARIS() 20130507: Implemented sub-screen to show WPM and allow changes before program starts main loop Implemented 10K potentiometer CT on pin A0 to control WPM from 5 to 40 Moved Morse Key to Analog Pin A3 in prep for reading Analog signal 20130505: Clean-up & module restructioning & migrating character arrays to PROGMEM decode() changed to char MagicMorse to return char and checked in main loop 20130501: Major change: Speed Pin D9 is now inverted to create Normally Low behavior NOTES: MiniPRO Pins: #__ Function_________________________________ A0 Center Tap of 10K pot to control WPM at bootup A1 n/a A2 n/a A3 Morse Key (other side of Key to Gnd) A4 n/a A5 n/a A6 n/a A7 n/a RESET Reset Tx 0 n/a (dedicated Serial Input) Rx 1 Diag Output RS232-TTL 9600 BAUD Async used for diagnostics: VT100 PIN 2 n/a PIN 3-7 Nokia Display (specifics below) PIN 8 Activate changes to NOKIA contrast B0 --> BF PIN 9 Activate Verbose Diagnostics by pulling LOW PIN 10 Force PARIS replay: tone & LCD, not diagnostic PIN 11 Tone Out --> approx 750Hz @5V to Piezo PIN 12 Green LED indicate DASH PIN 13 Red LED indicate DIT Nokia 5110 Graphic LCD Pinout: _______ Mini Pro____ _______ Nokia GLCD___ _____ test board cabling ___ #define PIN_SCE 7 LCD CE .... Pin 2 Yellow #define PIN_RESET 6 LCD RST .... Pin 1 Blue #define PIN_DC 5 LCD Dat/Com. Pin 3 (DC) Orange #define PIN_SDIN 4 LCD SPIDat . Pin 4 (DIN) White #define PIN_SCLK 3 LCD SPIClk . Pin 5 Brown // LCD Gnd .... Pin 2 Black // LCD Vcc .... Pin 8 Red 3.3V // LCD Vled ... Pin 7 Green (100 Ohms to Gnd) */ /* (c) Mickey R. Burnette, AKA: M. Ray Burne, author and software engineer: various blogs, Instructables, etc. Liquid Crystal library reference: http://arduino.cc/en/Reference/LiquidCrystal?from=Tutorial.LCDLibrary Timing semantics for Arduino published by Raron: http://raronoff.wordpress.com/2010/12/16/morse-endecoder/ Magic Morse Algorithm Copyright (c) 2011, 2012, 2013 by mrburnette and published at: http://code.google.com/p/morse-endecoder/wiki/Usage http://www.instructables.com/id/Morse-Code-Magic-An-Algorithm/ http://www.youtube.com/watch?v=9kZOqdeUl2w&feature=youtube_gdata http://www.picaxeforum.co.uk/showthread.php?19088-Morse-Code-Decoder-for-Cheap-using-a-20X2&p=177912#post177912 Contact Ray Burne: magic.morse @ gmail.com - All commercial rights reserved worldwide >>> Publically published articles with source grants end-use one (1) personal use license ONLY <<< Target compiles: ATmega328P - profile Mini w/328P @ 16MHz ☺ 20130525 - Version 8a Implemented Auto-setup for WPM and storing in EEPROM ☺ 20130525 - Version 8 Merged Nokia base routines with 2x16 LCD ☺ 20130523 - Version 6 Configured LCD on Bareboard to be same pinout as on MiniPro, same codebase ☺ 20130421 - Version 4. Board-duio version with LCD and variable resistor for speed timing ☺ 20121001 - Version .20 rewrite to eliminate object oriented code for faster inline ☺ 20120922 - Version .10 with WPM changes based on D0 ☺ 20120919 - Edited MM + code to allow some prosigns as in PICAXE code ☺ - Works from 25WPM to 40WPM using ARRL test files (w/ WPM = 30) ☺ 20120918 - Magic Morse Interface MM array implemented ClipperDigital ☺ - Works from 5WPM to 35WPM using ARRL test files (w/ WPM = 20) ☺ 20120917 - Initial code structual build from raron timing strutures // Interfacing requirements for use of digital I/O (NPN audio clipper circuit) 2.2K / 0.1uF (0.2) and input resistance 110 Ohms to 50 Ohms // Compile options: (commercial = UNO) MiniPro backpack 328P Board-duino lcd(7, 6, 2, 3, 4, 5) <ditto> * LCD RS pin to digital pin 7 " * LCD Enable pin to digital pin 6 " * LCD D7 pin to digital pin 5 " * LCD D6 pin to digital pin 4 " * LCD D5 pin to digital pin 3 " * LCD D4 pin to digital pin 2 " * LCD R/W pin to ground * 10K variable resistor (contrast): * ends to +5V and ground * wiper to LCD VO pin (pin 3) elements WPM tElements mS / element 50 5 250 240 50 10 500 120 50 15 750 80 50 20 1000 60 50 25 1250 48 50 30 1500 40 50 35 1750 34 50 40 2000 30 50 45 2250 27 50 50 2500 24 +-\/-+ Reset PC6 1| |28 PC5 (AI 5) Rx (D 0) PD0 2| |27 PC4 (AI 4) Tx (D 1) PD1 3| |26 PC3 (AI 3) Contact (non-Gnd) end of Morse Key LCD D4 (D 2) PD2 4| |25 PC2 (AI 2) LCD D5 PWM+ (D 3) PD3 5| |24 PC1 (AI 1) LCD D6 (D 4) PD4 6| |23 PC0 (AI 0) +5 VCC 7| |22 GND GND GND 8| |21 AREF XTL1 PB6 9| |20 AVCC XTL2 PB7 10| |19 PB5 (D 13) Green LED - DAH LCD D7 PWM+ (D 5) PD5 11| |18 PB4 (D 12) Red LED - DIT LCD E PWM+ (D 6) PD6 12| |17 PB3 (D 11) PWM (PWM 750Hz) to Piezo LCD RS (D 7) PD7 13| |16 PB2 (D 10) PWM Force PARIS (momentary Gnd) (D 8) PB0 14| |15 PB1 (D 9) PWM Verbose console option - Debug +----+ */