Echelon FTXL - Manual (Page 76)

64 Using the LonTalk Interface Developer Utility
Using Types
The LonTalk Interface Developer utility produces type definitions for the network
variables and configuration properties in your model file. For maximum
portability, all types defined by the utility are based on a small set of host-side
equivalents to the built-in Neuron C types. For example, the LonPlatform.h file
contains a type definition for a Neuron C signed integer equivalent type called
ncsInt. This type must be the equivalent of a Neuron C signed integer, a signed
8-bit scalar. For most target platforms, the ncsInt type is defined as signed char
type.
A network variable declared by a Neuron C built-in type does not require a host-
side type definition in the LonNvTypes.h file, but is instead declared with its
respective host-side Neuron C equivalent type as declared in LonPlatform.h.
Important: Network variables that use ordinary C types, such as int or long, are
not interoperable. For interoperability, network variables must use types defined
within the device resource files. These network variable types include standard
network variable types (SNVTs) and user-defined network variable types
(UNVTs). You can use the Resource Editor tool to define your own UNVT.
Example:
A model file contains the following declarations:
network input int nviInteger;
network output SNVT_count nvoCount;
network output SNVT_switch nvoSwitch;
• The nviInteger declaration uses a built-in Neuron-C type, so the LonTalk
Interface Developer utility uses the ncsInt type defined in LonPlatform.h.
• The nvoCount declaration uses a type that is not a built-in Neuron C
type. The utility produces the following type definition:
typedef ncuLong SNVT_count;
The ncuLong type represents the host-side equivalent of a Neuron C
unsigned long, a 16-bit unsigned scalar. It is defined in LonPlatform.h,
and typically maps to the LonWord type. LonWord is a platform-
independent definition of a 16-bit scalar in big-endian notation:
typedef struct {
LonByte msb;
LonByte lsb;
} LonWord;
To use this platform-independent type for numeric operations, you can
use the optional LON_GET_UNSIGNED_WORD or
LON_SET_UNSIGNED_WORD macros. Similar macros are provided for
signed words (16 bit), and for signed and unsigned 32-bit scalars
(DOUBLE).
Important: If a network variable or configuration property is defined
with an initializer in your device’s model file, and if you change the
default definition of multibyte scalars (such as the ncuLong type), you
must modify the initializer generated by the LonTalk Interface Developer
utility if the type is a multibyte scalar type.