148 lines
4.2 KiB
Plaintext
148 lines
4.2 KiB
Plaintext
subroutine genmsk144(msg0,mygrid,ichk,bcontest,msgsent,i4tone,itype)
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! s8 + 48bits + s8 + 80 bits = 144 bits (72ms message duration)
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!
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! Encode an MSK144 message
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! Input:
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! - msg0 requested message to be transmitted
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! - ichk if ichk=1, return only msgsent
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! if ichk.ge.10000, set imsg=ichk-10000 for short msg
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! - msgsent message as it will be decoded
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! - i4tone array of audio tone values, 0 or 1
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! - itype message type
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! 1 = standard message "Call_1 Call_2 Grid/Rpt"
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! 2 = type 1 prefix
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! 3 = type 1 suffix
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! 4 = type 2 prefix
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! 5 = type 2 suffix
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! 6 = free text (up to 13 characters)
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! 7 = short message "<Call_1 Call2> Rpt"
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use iso_c_binding, only: c_loc,c_size_t
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use packjt
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use hashing
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character*22 msg0
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character*22 message !Message to be generated
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character*22 msgsent !Message as it will be received
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character*6 mygrid
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integer*4 i4Msg6BitWords(13) !72-bit message as 6-bit words
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integer*4 i4tone(144) !
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integer*1, target:: i1Msg8BitBytes(10) !80 bits represented in 10 bytes
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integer*1 codeword(128) !Encoded bits before re-ordering
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integer*1 msgbits(80) !72-bit message + 8-bit hash
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integer*1 bitseq(144) !Tone #s, data and sync (values 0-1)
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integer*1 i1hash(4)
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integer*1 s8(8)
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logical bcontest
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real*8 pp(12)
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real*8 xi(864),xq(864),pi,twopi
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data s8/0,1,1,1,0,0,1,0/
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equivalence (ihash,i1hash)
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logical first
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data first/.true./
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save
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if(first) then
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first=.false.
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nsym=128
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pi=4.0*atan(1.0)
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twopi=8.*atan(1.0)
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do i=1,12
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pp(i)=sin((i-1)*pi/12)
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enddo
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endif
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if(msg0(1:1).eq.'@') then !Generate a fixed tone
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read(msg0(2:5),*,end=1,err=1) nfreq !at specified frequency
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go to 2
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1 nfreq=1000
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2 i4tone(1)=nfreq
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else
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message=msg0
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do i=1,22
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if(ichar(message(i:i)).eq.0) then
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message(i:)=' '
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exit
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endif
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enddo
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do i=1,22 !Strip leading blanks
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if(message(1:1).ne.' ') exit
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message=message(i+1:)
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enddo
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if(message(1:1).eq.'<') then
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call genmsk40(message,msgsent,ichk,i4tone,itype)
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if(itype.lt.0) go to 999
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i4tone(41)=-40
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go to 999
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endif
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call packmsg(message,i4Msg6BitWords,itype,bcontest) !Pack into 12 6-bit bytes
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call unpackmsg(i4Msg6BitWords,msgsent,bcontest,mygrid) !Unpack to get msgsent
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if(ichk.eq.1) go to 999
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i4=0
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ik=0
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im=0
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do i=1,12
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nn=i4Msg6BitWords(i)
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do j=1, 6
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ik=ik+1
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i4=i4+i4+iand(1,ishft(nn,j-6))
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i4=iand(i4,255)
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if(ik.eq.8) then
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im=im+1
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i1Msg8BitBytes(im)=i4
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ik=0
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endif
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enddo
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enddo
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ihash=nhash(c_loc(i1Msg8BitBytes),int(9,c_size_t),146)
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ihash=2*iand(ihash,32767) !Generate the 8-bit hash
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i1Msg8BitBytes(10)=i1hash(1) !Hash code to byte 10
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mbit=0
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do i=1, 10
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i1=i1Msg8BitBytes(i)
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do ibit=1,8
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mbit=mbit+1
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msgbits(mbit)=iand(1,ishft(i1,ibit-8))
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enddo
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enddo
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call encode_msk144(msgbits,codeword)
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!Create 144-bit channel vector:
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!8-bit sync word + 48 bits + 8-bit sync word + 80 bits
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bitseq=0
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bitseq(1:8)=s8
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bitseq(9:56)=codeword(1:48)
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bitseq(57:64)=s8
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bitseq(65:144)=codeword(49:128)
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bitseq=2*bitseq-1
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xq(1:6)=bitseq(1)*pp(7:12) !first bit is mapped to 1st half-symbol on q
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do i=1,71
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is=(i-1)*12+7
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xq(is:is+11)=bitseq(2*i+1)*pp
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enddo
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xq(864-5:864)=bitseq(1)*pp(1:6) !last half symbol
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do i=1,72
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is=(i-1)*12+1
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xi(is:is+11)=bitseq(2*i)*pp
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enddo
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! Map I and Q to tones.
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i4tone=0
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do i=1,72
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i4tone(2*i-1)=(bitseq(2*i)*bitseq(2*i-1)+1)/2;
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i4tone(2*i)=-(bitseq(2*i)*bitseq(mod(2*i,144)+1)-1)/2;
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enddo
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endif
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! Flip polarity
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i4tone=-i4tone+1
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999 return
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end subroutine genmsk144
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