Do you have the manual for the printer? I haven't
done this in many years, but I remember finding
everything I needed to know in the printer manual.
Maybe they don't make manuals as helpful as they
used to.
If you don't have the manual, see if you can find an
old Epson dot matrix printer manual. Fascinating
reading - really!
Here is function for graphics printing on Epson LX-300 fo 8051:
PrintVideo:
mov A,#27 ;set height of the string 1/8" 20/180"
lcall PrintByte
mov A,#48 ;
lcall PrintByte
mov DPTR,#PrintRAM ;
mov R7,#NumStr ;number of strings to print
PVCycle1: mov R6,#StrWide ;begin new string
mov A,#10 ;LF
lcall PrintByte
mov A,#13 ;CR
lcall PrintByte
mov A,#9 ;TAB
lcall PrintByte
mov A,#27 ;960 points per line
lcall PrintByte
mov A,#76
lcall PrintByte
mov A,#Low(StrWide*2) ;length of the string
lcall PrintByte
mov A,#High(StrWide*2)
lcall PrintByte