WSJT-X/lib/genmsk_128_90.f90

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Fortran
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subroutine genmsk_128_90(msg0,ichk,msgsent,i4tone,itype)
! s8 + 48bits + s8 + 80 bits = 144 bits (72ms message duration)
!
! Encode an MSK144 message
! Input:
! - msg0 requested message to be transmitted
! - ichk if ichk=1, return only msgsent
! if ichk.ge.10000, set imsg=ichk-10000 for short msg
! - msgsent message as it will be decoded
! - i4tone array of audio tone values, 0 or 1
! - itype message type
! 1 = standard message "Call_1 Call_2 Grid/Rpt"
! 2 = type 1 prefix
! 3 = type 1 suffix
! 4 = type 2 prefix
! 5 = type 2 suffix
! 6 = free text (up to 13 characters)
! 7 = short message "<Call_1 Call2> Rpt"
use iso_c_binding, only: c_loc,c_size_t
use packjt77
character*37 msg0
character*37 message !Message to be generated
character*37 msgsent !Message as it will be received
character*77 c77
integer*4 i4tone(144)
integer*1 codeword(128)
integer*1 msgbits(77)
integer*1 bitseq(144) !Tone #s, data and sync (values 0-1)
integer*1 s8(8)
real*8 pp(12)
real*8 xi(864),xq(864),pi,twopi
data s8/0,1,1,1,0,0,1,0/
equivalence (ihash,i1hash)
logical first,unpk77_success
data first/.true./
save
if(first) then
first=.false.
nsym=128
pi=4.0*atan(1.0)
twopi=8.*atan(1.0)
do i=1,12
pp(i)=sin((i-1)*pi/12)
enddo
endif
message(1:37)=' '
itype=1
if(msg0(1:1).eq.'@') then !Generate a fixed tone
read(msg0(2:5),*,end=1,err=1) nfreq !at specified frequency
go to 2
1 nfreq=1000
2 i4tone(1)=nfreq
else
message=msg0
do i=1, 37
if(ichar(message(i:i)).eq.0) then
message(i:37)=' '
exit
endif
enddo
do i=1,37 !Strip leading blanks
if(message(1:1).ne.' ') exit
message=message(i+1:)
enddo
if(message(1:1).eq.'<') then
i2=index(message,'>')
i1=0
if(i2.gt.0) i1=index(message(1:i2),' ')
if(i1.gt.0) then
call genmsk40(message,msgsent,ichk,i4tone,itype)
if(itype.lt.0) go to 999
i4tone(41)=-40
go to 999
endif
endif
i3=-1
n3=-1
call pack77(message,i3,n3,c77)
call unpack77(c77,msgsent,unpk77_success) !Unpack to get msgsent
if(ichk.eq.1) go to 999
read(c77,"(77i1)") msgbits
call encode_128_90(msgbits,codeword)
!Create 144-bit channel vector:
!8-bit sync word + 48 bits + 8-bit sync word + 80 bits
bitseq=0
bitseq(1:8)=s8
bitseq(9:56)=codeword(1:48)
bitseq(57:64)=s8
bitseq(65:144)=codeword(49:128)
bitseq=2*bitseq-1
xq(1:6)=bitseq(1)*pp(7:12) !first bit is mapped to 1st half-symbol on q
do i=1,71
is=(i-1)*12+7
xq(is:is+11)=bitseq(2*i+1)*pp
enddo
xq(864-5:864)=bitseq(1)*pp(1:6) !last half symbol
do i=1,72
is=(i-1)*12+1
xi(is:is+11)=bitseq(2*i)*pp
enddo
! Map I and Q to tones.
i4tone=0
do i=1,72
i4tone(2*i-1)=(bitseq(2*i)*bitseq(2*i-1)+1)/2;
i4tone(2*i)=-(bitseq(2*i)*bitseq(mod(2*i,144)+1)-1)/2;
enddo
endif
! Flip polarity
i4tone=-i4tone+1
999 return
end subroutine genmsk_128_90