WSJT-X/lib/genmsk144.f90

160 lines
4.6 KiB
Fortran
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subroutine genmsk144(msg0,ichk,msgsent,i4tone,itype,pchk_file)
!!!!!!!!!!!!!!!!!! Experimental small blocklength ldpc version
! s8 + 48bits + s8 + 80 bits = 144 bits (72ms message duration)
!
! Encode a JTMSK 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 packjt
use hashing
character*512 pchk_file,gen_file
character*22 msg0
character*22 message !Message to be generated
character*22 msgsent !Message as it will be received
integer*4 i4Msg6BitWords(13) !72-bit message as 6-bit words
integer*4 i4tone(144) !
integer*1, target:: i1Msg8BitBytes(10) !80 bits represented in 10 bytes
integer*1 codeword(128) !Encoded bits before re-ordering
integer*1 msgbits(80) !72-bit message + 8-bit hash
integer*1 bitseq(144) !Tone #s, data and sync (values 0-1)
integer*1 i1hash(4)
integer*1 b7(7)
integer*1 s8(8)
integer*1 b11(11)
integer*1 b13(13)
real*8 pp(12)
real*8 xi(864),xq(864),pi,twopi
data b7/1,1,1,0,0,1,0/
data s8/0,1,1,1,0,0,1,0/
data b11/1,1,1,0,0,0,1,0,0,1,0/ !Barker 11 code
data b13/1,1,1,1,1,0,0,1,1,0,1,0,1/ !Barker 13 code
equivalence (ihash,i1hash)
logical first
data first/.true./
save
i=index(pchk_file,".pchk")
gen_file=pchk_file(1:i-1)//".gen"
call init_ldpc(trim(pchk_file)//char(0),trim(gen_file)//char(0))
if( first ) then
first=.false.
nsym=128
pi=4.*atan(1.0)
twopi=8.*atan(1.0)
do i=1,12
pp(i)=sin( (i-1)*pi/12 )
enddo
endif
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=1,22
if(ichar(message(i:i)).eq.0) then
message(i:)=' '
exit
endif
enddo
do i=1,22 !Strip leading blanks
if(message(1:1).ne.' ') exit
message=message(i+1:)
enddo
if(message(1:1).eq.'<') then
call genmsk40(message,msgsent,ichk,i4tone,itype,pchk_file)
if(itype.lt.0) go to 999
i4tone(41)=-40
go to 999
endif
call packmsg(message,i4Msg6BitWords,itype) !Pack into 12 6-bit bytes
call unpackmsg(i4Msg6BitWords,msgsent) !Unpack to get msgsent
if(ichk.eq.1) go to 999
i4=0
ik=0
im=0
do i=1,12
nn=i4Msg6BitWords(i)
do j=1, 6
ik=ik+1
i4=i4+i4+iand(1,ishft(nn,j-6))
i4=iand(i4,255)
if(ik.eq.8) then
im=im+1
! if(i4.gt.127) i4=i4-256
i1Msg8BitBytes(im)=i4
ik=0
endif
enddo
enddo
ihash=nhash(c_loc(i1Msg8BitBytes),int(9,c_size_t),146)
ihash=2*iand(ihash,32767) !Generate the 8-bit hash
i1Msg8BitBytes(10)=i1hash(1) !CRC to byte 10
mbit=0
do i=1, 10
i1=i1Msg8BitBytes(i)
do ibit=1,8
mbit=mbit+1
msgbits(mbit)=iand(1,ishft(i1,ibit-8))
enddo
enddo
call ldpc_encode(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 genmsk144