Delta 36-R31 User Manual download pdf (Page 34)

ACC-36E Manual

USing acc-36E with power umac 34

Accessing ADCs from C Environment (For C Programmers)

Reading:

The GetPmacVar() function below allows one to read the ACC-36E structures in C. It is defined as

int GetPmacVar (char *pinstr, double *pdata), where:

- The first argument is a string containing the name of the variable to query.

- The second argument is a double containing the address of the ADC result (low or high).

Writing:

The SetPmacVar() function below allows writing to the ACC-36E structures in C. It is defined as:

int SetPmacVar (char *pinstr, double data), where:

- The first argument is a string containing the name of the variable to which to write.

- The second argument is a double containing the value to write.

WARNING

When using C routines, failure to release control of the loop

waiting for the ADC conversions to finish may cause PMAC to

lock up, possibly creating a runaway condition. Thus, one of the

following functions, WaitForADC(), has precautions in order to

release control of the wait loop in the event that the ADC

conversion bits never become 1.

Example: Unipolar Manual ADC Read in a CPLC

Configuring one ACC-36E with unipolar inputs at base offset $A00000.

#include <gplib.h>

#include <stdio.h>

#include <dlfcn.h>

// Definition(s)

#define FirstCardNumber 0 // At Base Offset $A00000

// Prototype(s)

int WaitForADC(unsigned int Card_Index);

void user_plcc() {

unsigned int ADC_Result_Unipolar[16],index;

int waitResult = 0;

char buffer[32]="";

double temp = 0,ConvertCode = 0;

// Access ADC results one by one in a for loop

for(index = 0; index < 8; index++) {

// Prepare string

sprintf(buffer,"ACC36E[%d].ConvertCode",FirstCardNumber);

ConvertCode = index; // Compute convert code

// Write Unipolar convert code to Channel Select structure

SetPmacVar(buffer,ConvertCode);

// Poll conversion complete bits until the conversions are finished

waitResult = WaitForADC(FirstCardNumber);

if(waitResult < 0)

{

return; // Conversion was not successful

}

// Prepare string

sprintf(buffer,"ACC36E[%d].ADCuLow",FirstCardNumber);

GetPmacVar(buffer,&temp); // Read the structure

// Cast and store low unipolar (unsigned) ADC Result in array element

ADC_Result_Unipolar[index] = (unsigned int)temp;

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