WSJT-X/lib/ft4/genft4.f90
2019-01-30 11:20:29 -05:00

77 lines
1.7 KiB
Fortran

subroutine genft4(msg0,ichk,msgsent,i4tone)
! Encode an FT4 message
! Input:
! - msg0 requested message to be transmitted
! - ichk if ichk=1, return only msgsent
! - msgsent message as it will be decoded
! - i4tone array of audio tone values, {0,1,2,3}
! Frame structure:
! s16 + 87symbols + 2 ramp up/down = 105 total channel symbols
! r1 + s4 + d29 + s4 + d29 + s4 + d29 + s4 + r1
! Message duration: TxT = 105*512/12000 = 4.48 s
! use iso_c_binding, only: c_loc,c_size_t
use packjt77
include 'ft4_params.f90'
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(NN),itmp(ND)
integer*1 codeword(2*ND)
integer*1 msgbits(77)
integer icos4(4)
logical unpk77_success
data icos4/0,1,3,2/
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
i3=-1
n3=-1
call pack77(message,i3,n3,c77)
call unpack77(c77,0,msgsent,unpk77_success) !Unpack to get msgsent
if(ichk.eq.1) go to 999
read(c77,"(77i1)") msgbits
call encode174_91(msgbits,codeword)
! Grayscale mapping:
! bits tone
! 00 0
! 01 1
! 11 2
! 10 3
do i=1,ND
is=codeword(2*i)+2*codeword(2*i-1)
if(is.le.1) itmp(i)=is
if(is.eq.2) itmp(i)=3
if(is.eq.3) itmp(i)=2
enddo
i4tone(1:4)=icos4
i4tone(5:33)=itmp(1:29)
i4tone(34:37)=icos4
i4tone(38:66)=itmp(30:58)
i4tone(67:70)=icos4
i4tone(71:99)=itmp(59:87)
i4tone(100:103)=icos4
999 return
end subroutine genft4