Remote-processing RPC-30 Manual de usuario descargar pdf (Pagina 23)

CHAPTER 6 DIGITAL AND OPTO PORTS

RPC-30 Page 21

The program below takes 1,000 samples and stores it in

an array. The time to read and store 1,000 samples is 2

seconds, or 2 ms per sample.

10 DIM F(1000)

20 FOR X = 0 TO 999

30 F(X) = AIN(1)

40 NEXT

Some applications require that measurements be made at

fixed intervals. T he ON TICK construct can be used to

take samples at timed intervals. The program below

reads 2 channels every second and stores it into an array.

When the array fills, the tick timer stops.

10 DIM F(800,2)

20 ON TICK 1 GOSUB 100

30 ..This is a dummy loop

40 GOTO 30

100 F(I,0) = AIN(0)

110 F(I,1) = AIN(1)

120 INC I

130 IF I = 800 THEN ON TICK 1 GOSUB

140 RETURN

The AOT statement outputs to a module. T he number is

in the range of 0 to 4095. The value of the output from

the G5 module is in proportion to the number.

To output to a G5 module, execute the following

command:

1000 AOT slot,value

slot ranges from 100 to 123 and corr esponds to the

number on an external opto rack. value ranges fr om 0 to

4095. The inter nal opto rack cannot be used for output.

Converting analog measureme nts

Input readings can be converted to usable units of

measurement by performing scaling calculations in the

program. The AIN function retur ns values fr om 0 to

511. To change these reading to other units, use the

following calculation:

variable = K * AIN(slot)

K is a scaling constant. It is obtained by diving the

highest measurement unit number by 511.

Example:

You want to measure a 0 to 200 PSI pressure

transducer with a 0 to + 5 volt output. Divide 200

by 511 to obtain the value of K.

K = 200 / 511

K = .3913894

To obtain the final value for the equation in PSI:

V = .3913894 * AIN (n)

DIGITAL I/O PORT

Digital I/O lines on the RPC-30 is supplied by an 82C55

chip. The chip' s lines go to connector J3.

Add 100 to CAM BASIC LINE and OP TO state ments to

access an individual port. For example, line 3 on the

STB boar d is accessed a s LIN E 103, ON. Opto module

position M7 is accessed as OPTO(107).

The lines on J3 are divided into 3 eight bit gr oups. Ports

A and B can be configured as all inputs or outputs. Port

C can be progr amed a s one group of 8 inputs or outputs

or as two groups of four lines (upper and lower C ). The

four lines in upper and lower C can each be programmed

as all inputs or outputs.

When a line is configured as an output, it can sink a

maximum of 2.5 ma at 0.4V and 15 ma at 1.0V.

The address for port A is 0, B is 1, and C is 2. The

CONFIG PIO statement is used to configure the 8255

lines. Use an address of 0.

Port B is connected to a high current sink through U1.

See "High current output" later in this chapter.

Pull up / down resistors

Digital I/O lines at J3 m ay be pulled up to + 5 volts or to

ground through a 10K resistor pack using jumper W6.

Jumper W6 for pull up or down configuration is as

follows:

[1-2] Pull up

[2-3] Pull down

Setting W6 for pull up makes interfacing to switches and

"open collector" TTL devices easy . See "Inter facing to

Switches and other devices" below.

1 2 ... 18 19 20 21 22 23 24 25 26 27 28 ... 37 38

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