titus-larsen-titus-1981-apple-interfacing

tion. Write a program that will perform the conversion to volta
You may add the steps to the program already in use.
We used the following steps which simply perform a mathemat·
conversion of the decimal value 0 to 255 to a corresponding volt
0 to +5 volts.
10 POKE 49319,0
20 FOR T = 0 TO 100: NEXT T
30 PRINT (PEEK(49319)*5/255)
40 GOTO 10
Try our program, or your own. Does it work
It should. You will see that the computer prints many decimal digi
probably too many, since the converter is only accurate to a ma
mum of one part in 256, or about 0.25%. Unfortunately, roundi
is not a trivial task in the Apple. You can perform either a math
matical rounding, or you can use a string operation to print only
selected number of digits after the decimal point. You can use t
following if you wish:
30 A$ = STR$(PEEK(49319)*5/255)
40 PRINT LEFT$ (A$,4)
50 GOTO 10
Remember that this routine simply limits the displayed value to fou
decimal digits. It does not perform any rounding.
Step 7
Try to write a routine that will use the high-resolution graphic
capability of the Apple computer, so that the program will plot th
voltage values with respect to time. The measurements should b
taken at a regular time (time-delay program) , and a continuou
line-plot should be drawn. If you are not familiar with the high
resolution graphics formats and commands, use the program provided
below:
100 HRG: HCOLOR = 3: Yl = O
110 FOR X = 0 TO 249
120 POKE 49319,0
158