If you have an interest in decoding Morse code here are some Procedures() snipped from some code I wrote.
I've also added a simple exerciser to show how it works. Compile it in Debug mode.
The tree based decoder has some advantages:
1 - There is no need to carry out a linear search when an end-of-character space is detected.
2 - It lends itself to decoding multiple input streams.
In a real-time decoder the characters would not all come in at the same time
In a multi channel application the variable *P would be one of an array from Dim *P(NumOfChans) and the channel number at any time probably derived from an FFT bin number, or group thereof.
73
RichardL (G8CDD)
Code: Select all
; This snip illustrates a method of decoding incoming morse code as symbols
; (Dits and Dahs) are received.
; (C)Richard Leman 2013
; Free to use at your own risk.
;{ Useful docs
; http://www.giangrandi.ch/electronics/radio/morse/morse.html
; http://www.learnmorsecode.com/
;}
Procedure Morse_BuildTree() ; Make a tree structured morse character table
; Each node has the address' of the nodes at the next level down and the character
; if this happens to be the last symbol.
; Returns the address of the entry node for use by decoders.
Protected *Table,CharCount,m,n,*P, AddMorse$,AddChar$
;{- Morse code table
DataSection
CodeList:
Data.s "a", ".-"
Data.s "b", "-..."
Data.s "c", "-.-."
Data.s "d", "-.."
Data.s "e", "."
Data.s "f", "..-."
Data.s "g", "--."
Data.s "h", "...."
Data.s "i", ".."
Data.s "j", ".---"
Data.s "k", "-.-"
Data.s "l", ".-.."
Data.s "m", "--"
Data.s "n", "-."
Data.s "o", "---"
Data.s "p", ".--."
Data.s "q", "--.-"
Data.s "r", ".-."
Data.s "s", "..."
Data.s "t", "-"
Data.s "u", "..-"
Data.s "v", "...-"
Data.s "w", ".--"
Data.s "x", "-..-"
Data.s "y", "-.--"
Data.s "z", "--.."
Data.s "0", "-----"
Data.s "1", ".----"
Data.s "2", "..---"
Data.s "3", "...--"
Data.s "4", "....-"
Data.s "5", "....."
Data.s "6", "-...."
Data.s "7", "--..."
Data.s "8", "---.."
Data.s "9", "----."
Data.s ".", ".-.-.-"
Data.s ",", "--..--"
Data.s "?", "..--.."
Data.s "'", ".----."
Data.s "!", "-.-.--"
Data.s "/", "-..-."
Data.s "(", "-.--."
Data.s ")", "-.--.-"
Data.s "&", ".-..."
Data.s ":", "---..."
Data.s ";", "-.-.-."
Data.s "=", "-...-"
Data.s "+", ".-.-."
Data.s "-", "-....-"
Data.s "_", "..--.-"
Data.s #DQUOTE$,".-..-."
Data.s "$", "...-..-"
Data.s "@", ".--.-."
EndDataSection
Debug "Number of characters = 54"
CharCount = 54
;}
Structure MORSE_NODE
DitBranch.i
DahBranch.i
NormLen.i
Char.s
EndStructure
Debug "Size of MORSE_NODE = " + Str(SizeOf(MORSE_NODE))
;- Memory for tree table
*Table = AllocateMemory((CharCount+12) * SizeOf(MORSE_NODE))
;- Create start node and first pair of sub-nodes
*MorseDat.MORSE_NODE = *Table
*MorseDat\DitBranch = *Table + SizeOf(MORSE_NODE)
*MorseDat\DahBranch = *Table + (2*SizeOf(MORSE_NODE))
*Empty = *Table + (3*SizeOf(MORSE_NODE)); Pointer to space for remaining nodes
;- Build tree
Restore CodeList
For m = 1 To CharCount
Read.s AddChar$ : Read.s AddMorse$
Debug ""
Debug Str(m)+" " + AddChar$+" "+AddMorse$+" ("+Str(Len(AddMorse$))+ " Symbols)"
*P = *Table ; Entry point to table
For n = 1 To Len(AddMorse$)
*MorseDat.MORSE_NODE = *P
With *MorseDat
Select Mid(AddMorse$,n,1)
Case "-" ; Got a DAH...
If \DahBranch = 0 ; If no DAH branch...
\DahBranch = *Empty ; use an Empty node...
*Empty + SizeOf(MORSE_NODE) ; make a new empty node for later
EndIf
*P = \DahBranch
Debug "DAH "+Str(*P-*Table)
Case "." ; Got a DIT...
If \DitBranch = 0
\DitBranch = *Empty
*Empty + SizeOf(MORSE_NODE)
EndIf
*P = \DitBranch
Debug "DIT "+Str(*P-*Table)
EndSelect
EndWith
Next
*MorseDat.MORSE_NODE = *P
*MorseDat\Char = AddChar$
Next
ProcedureReturn *Table
EndProcedure
Procedure Morse_GotDit(*K) ; A DIT has been received, move down the tree from current tree position
*MorseDat.MORSE_NODE = *K
*K = *MorseDat\DitBranch
ProcedureReturn *K
EndProcedure
Procedure Morse_GotDah(*K) ; A DAH has been received, move down the tree from current tree position
*MorseDat.MORSE_NODE = *K
*K = *MorseDat\DahBranch
ProcedureReturn *K
EndProcedure
Procedure.s Morse_GetChar(*K) ; An end of char space was detected, get the character at the current tree position
*MorseDat.MORSE_NODE = *K
ProcedureReturn *MorseDat\Char
EndProcedure
; Demo
*MorseTable = Morse_BuildTree() ; Build table
*P = *MorseTable ; Init pointer
Repeat
k$ = InputRequester("Morse entry","Type a string of Dits and Dahs ('.' and '-')","")
If k$ = "" : Break : EndIf
For n = 1 To Len(k$) ; For each symbol...
Select Mid(k$,n,1)
Case "." : *P=Morse_GotDit(*P) ; It is a '.' so move down the table.
Case "-" : *P=Morse_GotDah(*P) ; It is a '-' so move down teh table.
Default : *P = 0 : Break ; Typo in input.
EndSelect
Next
If *P
Debug Morse_GetChar(*P)
EndIf
*P = *MorseTable ; Re-init pointer ready for next symbol/char
ForEver
