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An all-Fortran implementation of Q65 source encoding, CRC calculation, and LDPC coding, for reference.
This commit is contained in:
Steven Franke
parent
f289bb06bb
commit
79140b4430
235
lib/qra/q65/q65code.f90
Normal file
235
lib/qra/q65/q65code.f90
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@ -0,0 +1,235 @@
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module gf64math
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! add and subtract in GF(2^6) based on primitive polynomial x^6+x+1
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implicit none
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integer, private :: gf64log(0:63)
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integer, private :: gf64antilog(0:62)
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! table of the logarithms of the elements of GF(M) (log(0) never used)
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data gf64log/ &
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-1, 0, 1, 6, 2, 12, 7, 26, 3, 32, &
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13, 35, 8, 48, 27, 18, 4, 24, 33, 16, &
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14, 52, 36, 54, 9, 45, 49, 38, 28, 41, &
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19, 56, 5, 62, 25, 11, 34, 31, 17, 47, &
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15, 23, 53, 51, 37, 44, 55, 40, 10, 61, &
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46, 30, 50, 22, 39, 43, 29, 60, 42, 21, &
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20, 59, 57, 58/
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! table of GF(M) elements given their logarithm
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data gf64antilog/ &
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1, 2, 4, 8, 16, 32, 3, 6, 12, 24, &
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48, 35, 5, 10, 20, 40, 19, 38, 15, 30, &
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60, 59, 53, 41, 17, 34, 7, 14, 28, 56, &
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51, 37, 9, 18, 36, 11, 22, 44, 27, 54, &
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47, 29, 58, 55, 45, 25, 50, 39, 13, 26, &
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52, 43, 21, 42, 23, 46, 31, 62, 63, 61, &
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57, 49, 33/
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contains
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integer function gf64_add(i1,i2)
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implicit none
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integer::i1
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integer::i2
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gf64_add=iand(ieor(i1,i2),63)
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end function gf64_add
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integer function gf64_mult(i1,i2)
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implicit none
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integer::i1
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integer::i2
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integer::j
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if(i1.eq.0 .or. i2.eq.0) then
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gf64_mult=0
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elseif(i1.eq.1) then
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gf64_mult=i2
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elseif(i2.eq.1) then
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gf64_mult=i1
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else
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j=mod(gf64log(i1)+gf64log(i2),63)
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gf64_mult=gf64antilog(j)
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endif
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end function gf64_mult
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end module gf64math
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module q65_generator
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integer generator(15,50)
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data generator/ &
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, &
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0,20, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, &
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0,20, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, &
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0,20, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, &
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0,20, 0, 1, 1, 0, 0, 0,10, 0, 0, 0, 0, 1, 0, &
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0,20, 0, 1, 1, 0, 0, 0,10, 0, 0, 0,44, 1, 0, &
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0,20, 0, 1, 1, 0, 0, 0,10, 1, 0, 0,44, 1, 0, &
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0,20, 0, 1, 1, 0, 0, 0,10, 1, 0, 0,44, 1,14, &
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0,20, 0, 1, 1, 0, 0, 0,10, 1,31, 0,44, 1,14, &
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0,20, 0, 1, 1,33, 0, 0,10, 1,31, 0,44, 1,14, &
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56,20, 0, 1, 1,33, 0, 0,10, 1,31, 0,44, 1,14, &
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56,20, 0, 1, 1,33, 0, 1,10, 1,31, 0,44, 1,14, &
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56, 1, 0, 1, 1,33, 0, 1,10, 1,31, 0,44, 1,14, &
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56, 1, 0, 1, 1,33, 0, 1,10, 1,31,36,44, 1,14, &
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56, 1, 0, 1, 1,33, 0, 1,43, 1,31,36,44, 1,14, &
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56, 1, 0, 1, 1,33, 0, 1,43,17,31,36,44, 1,14, &
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56, 1, 0, 1, 1,33, 0, 1,43,17,31,36,36, 1,14, &
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56, 1, 0, 1, 1,33,53, 1,43,17,31,36,36, 1,14, &
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56, 1, 0,35, 1,33,53, 1,43,17,31,36,36, 1,14, &
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56, 1, 0,35, 1,33,53, 1,43,17,30,36,36, 1,14, &
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56, 1, 0,35, 1,33,53,52,43,17,30,36,36, 1,14, &
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56, 1, 0,35, 1,32,53,52,43,17,30,36,36, 1,14, &
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56, 1,60,35, 1,32,53,52,43,17,30,36,36, 1,14, &
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56, 1,60,35, 1,32,53,52,43,17,30,36,36,49,14, &
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56, 1,60,35, 1,32,53,52,43,17,30,36,37,49,14, &
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56, 1,60,35,54,32,53,52,43,17,30,36,37,49,14, &
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56, 1,60,35,54,32,53,52, 1,17,30,36,37,49,14, &
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1, 1,60,35,54,32,53,52, 1,17,30,36,37,49,14, &
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1, 0,60,35,54,32,53,52, 1,17,30,36,37,49,14, &
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1, 0,60,35,54,32,53,52, 1,17,30,37,37,49,14, &
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1, 0,61,35,54,32,53,52, 1,17,30,37,37,49,14, &
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1, 0,61,35,54,32,53,52, 1,48,30,37,37,49,14, &
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1, 0,61,35,54,32,53,52, 1,48,30,37,37,49,15, &
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1, 0,61,35,54, 0,53,52, 1,48,30,37,37,49,15, &
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1, 0,61,35,54, 0,52,52, 1,48,30,37,37,49,15, &
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1, 0,61,35,54, 0,52,52, 1,48,30,37,37, 0,15, &
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1, 0,61,35,54, 0,52,34, 1,48,30,37,37, 0,15, &
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1, 0,61,35,54, 0,52,34, 1,48,30,37, 0, 0,15, &
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1, 0,61,35,54, 0,52,34, 1,48,30,20, 0, 0,15, &
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1, 0, 0,35,54, 0,52,34, 1,48,30,20, 0, 0,15, &
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1, 0, 0,35,54, 0,52,34, 1, 0,30,20, 0, 0,15, &
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0, 0, 0,35,54, 0,52,34, 1, 0,30,20, 0, 0,15, &
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0, 0, 0,35,54, 0,52,34, 1, 0,38,20, 0, 0,15, &
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0, 0, 0,35, 0, 0,52,34, 1, 0,38,20, 0, 0,15, &
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0, 0, 0,35, 0, 0,52, 0, 1, 0,38,20, 0, 0,15, &
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0, 0, 0,35, 0, 0,52, 0, 1, 0,38,20, 0, 0, 0, &
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0, 0, 0,35, 0, 0,52, 0, 0, 0,38,20, 0, 0, 0, &
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0, 0, 0,35, 0, 0,52, 0, 0, 0,38, 0, 0, 0, 0, &
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0, 0, 0, 0, 0, 0,52, 0, 0, 0,38, 0, 0, 0, 0, &
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0,38, 0, 0, 0, 0/
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end module q65_generator
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subroutine q65_encode(message,codeword)
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use gf64math
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use q65_generator
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integer message(15)
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integer codeword(65)
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integer i,j
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codeword=0
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codeword(1:15)=message
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do i=1,15
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do j=16,65
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codeword(j)=gf64_add(codeword(j),gf64_mult(message(i),generator(i,j-15)))
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enddo
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enddo
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return
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end
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subroutine get_q65crc12(mc2,ncrc1,ncrc2)
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!
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character c12*12,c6*6
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integer*1 mc(90),mc2(90),tmp(6)
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integer*1 r(13),p(13)
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integer ncrc,nnn
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! polynomial for 12-bit CRC 0xF01
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data p/1,1,0,0,0,0,0,0,0,1,1,1,1/
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! flip bit order of each 6-bit symbol for consistency with Nico's calculation
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do i=0,12
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tmp=mc2(i*6+1:i*6+6)
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mc(i*6+1:i*6+6)=tmp(6:1:-1)
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enddo
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! divide by polynomial
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r=mc(1:13)
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do i=0,77
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r(13)=mc(i+13)
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r=mod(r+r(1)*p,2)
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r=cshift(r,1)
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enddo
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write(c6,'(6b1)') r(6:1:-1)
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read(c6,'(b6.6)') ncrc1
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read(c6,'(6b1)') mc2(79:84)
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write(c6,'(6b1)') r(12:7:-1)
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read(c6,'(b6.6)') ncrc2
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read(c6,'(6b1)') mc2(85:90)
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end subroutine get_q65crc12
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program q65code
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use packjt77
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implicit none
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character msg*37,msgsent*27,arg*12,c12*12,c6*6
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integer message(15)
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integer codeword(65), shortcodeword(63)
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integer isync(22)
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integer itone(85)
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integer i,j,k
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integer nargs,ncrc1,ncrc2,ncrc
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integer i3,n3
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integer*1 mbits(90)
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integer msymbols(15)
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character*77 c77
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data isync/1,9,12,13,15,22,23,26,27,33,35,38,46,50,55,60,62,66,69,74,76,85/
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nargs=iargc()
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if(nargs .ne. 1) then
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print*,'Usage: q65sf "msg"'
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goto 999
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endif
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call getarg(1,msg)
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i3=-1
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n3=-1
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call pack77(msg,i3,n3,c77)
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mbits=0
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read(c77,'(77i1)') mbits(1:77)
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! Message is 77 bits long. Add a 0 bit to create a 78-bit message and pad with
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! 12 zeros to create 90-bit mbit array for CRC calculation.
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call get_q65crc12(mbits,ncrc1,ncrc2)
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! Now have message in bits 1:78 and CRC in bits 79:90.
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! Group message bits into 15 6-bit symbols:
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do i=0,14
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write(c6,'(6i1)') mbits( (i*6+1):(i*6+6) )
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read(c6,'(b6.6)') message(i+1)
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enddo
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! Encode to create a 65-symbol codeword
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call q65_encode(message,codeword)
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write(*,*) 'Generated message plus CRC (90 bits)'
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write(*,'(a8,15i4)') '6 bit : ',message
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write(*,'(a8,90i1)') 'binary: ',mbits
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write(*,*) ' '
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write(*,*) 'Codeword with CRC symbols (65 symbols)'
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write(*,'(20i3)') codeword
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!Shorten the codeword by omitting the CRC symbols (symbols 14 and 15)
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shortcodeword(1:13)=codeword(1:13)
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shortcodeword(14:63)=codeword(16:65)
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!Insert sync symbols to create array of channel symbols
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j=1
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k=0
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do i=1,85
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if(i.eq.isync(j)) then
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j=j+1
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itone(i)=0
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else
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k=k+1
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itone(i)=shortcodeword(k)+1
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endif
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enddo
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write(*,*) ' '
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write(*,*) 'Channel symbols (85 total)'
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write(*,'(20i3)') itone
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999 end program q65code
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