APPENDIX E:
LX
200
PERSONAL COMPUTER CONTROL
Remote operation of a computerized telescope has been only a
dream for most amateur astronomers. The realization of fully
controlling a telescope through a personal computer has been
expensive and has required expert knowledge of software and
hardware.
The LX200’s internal software supports the RS-232 interface,
requiring only a serial communication program, such as
Procomm. With a serial communication program, you can use
the individual commands from the LX200 command set to
simulate keypad control functions of the LX200. A simple RS-232
connection to virtually any computer makes all LX200 commands
and modes available. You can use a PC to explore the object
library, adjust slewing speeds, or adjust focus with the optional
#1206 Electric Focuser.
If you are not a professional programmer, but wish to explore
remote operation of the LX200 with your computer, there are
after-market software programs available specifically for the
LX200, including AstroSearch from Meade Instruments Corp.
This appendix provides the following:
Schematic for constructing your own RS-232 cable
LX200 TEST program to test the RS-232 communication line
LX200 command set
LX200 DEMO, which is a program that you can enter into your
computer to access the object library, slew to the object, and
center the image
RS-232 Cable
The input hardware uses a standard six-line telephone jack
connector, pre-attached to a six-conductor flat line telephone-
style cable (of any length, up to 100-feet and perhaps even more,
depending on the gauge of the cable). You also need either a
nine-pin or 25-pin RS-232 connector, whichever your computer
uses for the serial port. All the above items are available at most
electronics hardware stores.
Fig. 18 shows the LX200 pinouts for the six-line telephone
connector. The table below shows standard IBM-compatible DB-
9 and DB-25 serial port pinouts, and how to connect them to the
LX200 six-line modular connector.
NOTE:Only 3 wires are required.
LX200 TEST Program
Once you have the RS-232 cable constructed, test it with the
following program (LX200 TEST). This program is written in GW
Basic programming language; it will work with virtually any IBM-
compatible computer. LX200 TEST is an effective program for
fully checking RS-232 line communications from your PC to the
LX200. It lets you concentrate on debugging your RS-232 cable.
Fig.18: LX200 modular connector.
LX200 RS-232 CONNECTOR PIN OUT CODE LEGEND
6 WIRE MODULAR
DESCRIPTION
TO DB-9 CONNECTOR
TO DB-25
CONNECTOR
PIN#
CONNECTOR PIN#
#1
+12 VOLTS DC
NOT USED
NOT USED
#2
MISC. SERIALOUT
NOT USED
NOT USED
#3
PC TRANSMIT DATA
#3
#2
#4
GROUND
#5
#7
#5
PC RECEIVE DATA
#2
#3
#6
MISC. SERIALIN
NOT USED
NOT USED
10 CLS
20 DEFINTA-X
30 OPEN "COM1:9600,N,8,1,CD0,CS0,DS0,RS," FOR
RANDOM AS #1
50 key1$ = INKEY$: IF key1$ = "" THEN GO TO 50
60 REM KEY1S
70 IF key1$ = CHR$(119) THEN GOSUB 200: REM "w" key
80 IF key1$ = CHR$(101) THEN GOSUB 200: REM "e" key
90 IF key1$ = CHR$(110) THEN GOSUB 200: REM "n" key
100 IF key1$ = CHR$(115) THEN GOSUB 200: REM "s" key
105 IF key1$ = "x" THEN END: REM To exit test.
110 GO TO 50
120 END
200 REM directions
210 REM west
220 IF key1$ = "w" THEN a$ = "#:Mw#": PRINT #1, a$: REM GO
west
230 REM east
240 IF key1$ = "e" THEN a$ = "#:Me#": PRINT #1, a$: REM GO
east
250 REM north
260 IF key1$ = "n" THEN a$ = "#:Mn#": PRINT #1, a$: REM GO
north
270 REM south:
280 IF key1$ = "s" THEN a$ = "#:Ms#": PRINT #1, a$: REM GO
south
290 key1$ = INKEY$:
300 IF key1$ = CHR$(32) THEN GO TO 400 ELSE GO TO 200
400 REM This stops motion (by hitting SPACE bar).
410 B$ = "#:Qe#": PRINT #1, B$
420 B$ = "#:Qw#": PRINT #1, B$
430 B$ = "#:Qn#": PRINT#1, B$
440 B$ = "#:Qs#": PRINT #1, B$
450 RETURN
460 END
- 51 -
Telescope
Panel
Connector
6
3
5
2
4
1
