National Instruments Welding System 321645c-01 Manual De Usuario

Chapter 2

Function Reference — GPCTR_Change_Parameter

NI-DAQ FRM for PC Compatibles

2-202

National Instruments Corporation

Synchronization on default Source and Up/Down pins is enabled when you call

GPCTR_Change_Parameter

with paramID =

ND_INPUT_CONDITIONING

and

paramValue as any of the quadrature modes or the two-pulse counting mode.

You can enable Z-Index pulse for quadrature encoders by making a

GPCTR_Change_Parameter

call with paramID =

ND_INDEX_PULSE

and

paramValue =

ND_YES

. The Z-Index signal should be connected to default gate for the

counter that is being used. The value to which the count should reset in the event of a Z-Index
pulse can be specified by making a

GPCTR_Change_Parameter

call with paramID =

ND_COUNT_1.

Note

By default, the counter will start counting from 0. You can alter this by calling

GPCTR_Change_Parameter

with a paramID set to

ND_INITIAL_COUNT

. A good

technique for setting the initial value would be to set it in an invalid range. When
the counter receives a Z-Index, the value of the counter will be placed in a valid
range. This technique will allow you to detect the initial Z-Index.

An example use of this paramID is shown below:

Create u32 variable gpctrNum;

Create u32 variable counterValue;

gpctrNum = ND_COUNTER_0

GPCTR_Control (deviceNumber, gpctrNum, ND_RESET)

GPCTR_Control (deviceNumber, gpctrNum, ND_SIMPLE_CNT)

GPCTR_Change_Parameter (deviceNumber, gpctrNum,

ND_INPUT_CONDITIONING,ND_QUADRATURE_ENCODER_X1)

/*specify that the counter reloads to value of 1000 every time a

Z-Index pulse occurs*/

GPCTR_Change_Parameter (deviceNumber, gpctrNum, ND_Z_INDEX_PULSE,

1000)

/*load the counter initially with a bogus value for Z-Index

detection*/

GPCTR_Change_Parameter (deviceNumber, gpctrNum, ND_COUNT_1, –10000)

GPCTR_Control (deviceNumber, gpctrNum, ND_PROGRAM)

Repeat as long as required by your application

{

/*you can check for a valid value for counterValue here*/

GPCTR_Watch (deviceNumber, gpctrNum, ND_COUNT, counterValue)