DIO__GetDeviceValue (ul_pbar_dio)

 *  Synopsis:
 *    #include <ul_pbar_dio:dio.h>
 *
 *    float *DIO__GetDeviceValue( const CDIOptr devicePtr, float *deviceValue )
 *
 *  Function intent:
 *    DIO__GetDeviceUnits() returns a pointer to the DIO device value obtained
 *    in a previous call to DIO__ReadDeviceValue() for the device pointed to by
 *    devicePtr.  If parameter deviceValue is not NULL the routine places the
 *    value in memory pointed to by deviceValue and returns deviceValue.  If
 *    parameter deviceValue is NULL the routine returns a pointer to the DIO__
 *    system's copy of the value.
 *  Function parameters:
 *    CDIOptr	devicePtr	The unique DIO device I/O control pointer
 *                              returned by DIO__InitializeModule().
 *    float	*deviceValue	destination array of LEN_DEV_UNITS + 1 bytes
 *  Function return value:
 *    none