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91 lines
2.2 KiB
Fortran
91 lines
2.2 KiB
Fortran
subroutine genft4(msg0,ichk,msgsent,msgbits,i4tone)
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! Encode an FT4 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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! - msgsent message as it will be decoded
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! - i4tone array of audio tone values, {0,1,2,3}
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! Frame structure:
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! s16 + 87symbols + 2 ramp up/down = 105 total channel symbols
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! r1 + s4 + d29 + s4 + d29 + s4 + d29 + s4 + r1
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! Message duration: TxT = 105*576/12000 = 5.04 s
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! use iso_c_binding, only: c_loc,c_size_t
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use packjt77
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include 'ft4_params.f90'
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character*37 msg0
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character*37 message !Message to be generated
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character*37 msgsent !Message as it will be received
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character*77 c77
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integer*4 i4tone(NN),itmp(ND)
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integer*1 codeword(2*ND)
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integer*1 msgbits(77),rvec(77)
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integer icos4a(4),icos4b(4),icos4c(4),icos4d(4)
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logical unpk77_success
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data icos4a/0,1,3,2/
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data icos4b/1,0,2,3/
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data icos4c/2,3,1,0/
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data icos4d/3,2,0,1/
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data rvec/0,1,0,0,1,0,1,0,0,1,0,1,1,1,1,0,1,0,0,0,1,0,0,1,1,0,1,1,0, &
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1,0,0,1,0,1,1,0,0,0,0,1,0,0,0,1,0,1,0,0,1,1,1,1,0,0,1,0,1, &
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0,1,0,1,0,1,1,0,1,1,1,1,1,0,0,0,1,0,1/
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message=msg0
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do i=1, 37
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if(ichar(message(i:i)).eq.0) then
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message(i:37)=' '
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exit
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endif
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enddo
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do i=1,37 !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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i3=-1
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n3=-1
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call pack77(message,i3,n3,c77)
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call unpack77(c77,0,msgsent,unpk77_success) !Unpack to get msgsent
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if(ichk.eq.1) go to 999
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read(c77,'(77i1)',err=1) msgbits
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if(unpk77_success) go to 2
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1 msgbits=0
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itone=0
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msgsent='*** bad message *** '
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go to 999
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entry get_ft4_tones_from_77bits(msgbits,i4tone)
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2 msgbits=mod(msgbits+rvec,2)
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call encode174_91(msgbits,codeword)
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! Grayscale mapping:
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! bits tone
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! 00 0
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! 01 1
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! 11 2
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! 10 3
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do i=1,ND
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is=codeword(2*i)+2*codeword(2*i-1)
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if(is.le.1) itmp(i)=is
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if(is.eq.2) itmp(i)=3
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if(is.eq.3) itmp(i)=2
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enddo
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i4tone(1:4)=icos4a
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i4tone(5:33)=itmp(1:29)
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i4tone(34:37)=icos4b
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i4tone(38:66)=itmp(30:58)
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i4tone(67:70)=icos4c
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i4tone(71:99)=itmp(59:87)
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i4tone(100:103)=icos4d
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999 return
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end subroutine genft4
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