Diagonal Movement

If you have always wanted a joystick for your Sinclair, but were a little intimidated about making hardware modifications, the article -“Adding a Joystick to the Timex-Sinclair 1000” by James Stephens, SYNC, Vol 3, No 4 Jul/Aug 1983, page 52 is for you. It shows a simple inexpensive way to add an atari type joystick.The only catch is that the program listed in the article provides only for up-down and left – right movement – it will not do the diagonals. The following program uses the system variable LAST K instead of the function INKEY$. LAST-K (PEEK 16421 + 256 * PEEK 16422), provides a useful value even with two or more keys simultaneously depressed, exactly what we need for diagonals. The program is a little slow as it stands, but it maybe compiled (using Bob Beach’s compiler), without changes. The resulting machine code is surprisingly fast.

The program listing:

001  SLOW
005  LET X = 20
007  LET Y = 20
010  LET A = PEEK 16422
015  LET B = PEEK 16421
020  IF A = 255 THEN GOTO 10
040  IF A <> 223 THEN GOTO 80
050  IF B <> 239 THEN GOTO 60
052  LET Y = Y - 1
056  GOTO 500
060  IF B <> 247 THEN GOTO 70
062  LET X = X - 1
066  GOTO 500
070  LET X = X - 1
072  LET Y = Y - 1
076  GOTO 500
080  IF A <> 239 THEN GOTO 100
085  LET Y = Y + 1
090  GOTO 500
100  IF A <> 247 THEN GOTO 130
110  LET X = X + 1
120  GOTO 500
130  IF A <> 207 THEN GOTO 170
140  LET X = X - 1
150  LET Y = Y + 1
160  GOTO 500
170  IF A <> 215 THEN GOTO 210
180  LET X = X + 1
190  LET Y = Y - 1
200  GOTO 500
210  IF A <> 231 THEN GOTO 290
220  LET X = X - 1
230  LET Y = Y + 1
240  GOTO 500
290  IF A <> 253 THEN GOTO 10
300  RETURN
500  IF X > 63 THEN LET X = 63
510  IF X < 0 THEN LET X = 0
520  IF Y > 43 THEN LET Y = 43
530  IF Y < 0 THEN LET Y = 0
570  PLOT X,Y
600  GOTO 10

enter the program and RUN – use the ” magic arrow ” keys, 5, 6, 7, 8 to move the dot around- try pressing two keys in combination.