24/7 Data Acquisition Wildcard Users Guide

<< Previous | Next>>

FORTH: Start_Conversion ( b1\u\b2\b3\b4\b5\b6 -- flag )
C: int Start_Conversion( char cal_type, uint freq_int, char gain, char pol, char res, char bo, char ch )

Starts a conversion by configuring the specified channel with the specified options. It interrupts the A/D from its current operation, reconfigures it, and commences repetitive conversions. Init_AD24 and Use_Onboard_Ref or Use_External_Ref must be called prior to this routine to initialize the 24/7 Data Acquisition Wildcard. Error checking is done for each option and an error flag is returned if an invalid parameter is used. Note that the flag validates input parameters, not calibration results. The parameters and their allowed values are provided in the following table:

data acquisition board: conversion parameters and allowed values

This routine is not re-entrant. If used in a multitasking system, ensure that only one task calls this routine or that separate tasks do not use the AD7714 at the same time. If several calibrations are performed in sequence each must be allowed to run to completion before initiating the next. Because Start_Conversion returns before the calibration is complete, to ensure that a calibration is complete before initiating the next you should call AD24_Sample, Read_FS_Cal, or Read_Zero_Cal in between as those routines wait for sample completion before returning.

This routine takes 3.08 ms to start a conversion and 5.08 ms to execute.

FORTH: Stop_Conversion ( -- )
C: void Stop_Conversion ( void )

Disconnects the 24 bit analog to digital converter from its analog field inputs including the voltage references. Called in Init_AD24 and Reset_AD24. Does not stop the AD7714 from doing repetitive conversions, but does disconnect its inputs.

FORTH: Sync ( -- ) C: void Sync ( void )

Resets the modulator and digital filter of the analog to digital converter without affecting any of the setup conditions. This allows you to start gathering samples from the analog input from a known point in time (once the routine is executed). 3 sample periods must elapse before the next valid sample is available. See pages 26 and 27 of the data sheet for more information.

FORTH: Use_External_Ref ( -- )
C: void Use_External_Ref ( void )

Connects pins 9 (FDREF+) and 11 (FDREF−) as the 24 bit analog to digital converter's reference and disconnects the on-board reference voltage. The external reference may be derived from any external source, or from the WildCard�s reference output (pins 7 for REF+ and 13 for REF−), so long as the reference voltage magnitued (REF+ − REF−) is in the range of +1V to +2.5V and lies within the common mode input range of the A/D (0-5V with the buffer off, 0-3.5V with the buffer on).

This routine must be used after Init_AD24 or Stop_Conversion and before Start_Conversion or Start_Conv_With_Valuesto restore the reference connection before a calibration is done.

FORTH: Use_Onboard_Ref ( -- ) C: void Use_Onboard_Ref ( void )

Connects the on-board 2.5 volt reference to the 24 bit analog to digital converter and disconnects the external reference voltage. Must be used after Init_AD24 or Stop_Conversion and before Start_Conversion or Start_Conv_With_Values to restore the reference connection before a calibration is done.

<< Previous | Next>>

Table of Contents

24/7 Data Acquisition Wildcard Users Guide