1. David Gay Intel Research Berkeley
nesC 1.2
David Gay
Intel Research Berkeley
nesC is a PL for a new area, n.e.s.
nesC is the PL used to implement TinyOS, our OS for n.e.s., and its apps
nesC and TinyOS tightly intertwined; designed together to address 1! challenges of this area
I’ll start by introducing n.e.s, typical apps and the resulting challenges
I will then show how nesC and TinyOS address these challenges

2. Introduction nesC 1.2 is a major revision to the nesC language Goals
“external” types (with Kevin Chang, UCLA)
generic components
binary components
attributes
Goals
simplify TinyOS programming
make it easier to define new abstractions and services

3. External Types: Why? Current message formats defined as C structures
machine-dependent representation
different padding
different endianness
Until recently, not a problem:
homogeneous networks, with platform-specific radios
mig tool decodes structures for PCs
Now: on telos, micaz, imote2
want interoperability!

4. Standard Solutions Marshalling/unmarshalling:
needs extra RAM
protocol stack built by wiring components, so no obvious central place to do marshalling/unmarshalling
Unix-style htons, htonl, etc calls
programmer-unfriendly
only addresses endiannness
gcc’s “packed” attribute
only addresses padding

5. External Types
nesC 1.2 introduces “external types”, which have a platform-independent representation:
OLD NEW
struct TOSMsg { nx_struct TOSMsg {
uint16_t addr; nx_uint16_t addr;
uint8_t group; nx_uint8_t group;
… …
nx_structs have no padding
nx_uint16_t, etc are big-endian on all platforms
these types can be used like any C types (some minor restrictions)
Very easy to convert TinyOS code to use external types

6. Generic Components
Components with numeric and type arguments, that can be instantiated at compile-time
Interfaces can also have type arguments
Uses:
utility components: filters, adapters, queues, buffers, etc
wiring patterns: see OSKI
generic module QueueC(typedef t, int n) {
provides interface Queue<t>;
} implementation {
t q[n]; … }
configuration App { }
implementation {
components AppM,
new QueueC(TOSMsg, 10) as MyQ;
AppM.MsgQ -> MyQ; }

7. Other Changes (in brief)
Attributes (inspired by Java 1.5)
programmers can add custom annotations to nesC programs
external tools can extract program information
uses: wiring checks, network management attributes, etc
Binary components
compile nesC “app” to .o file with specified entry, exit points
uses:
build, use, distribute components in binary form
encapsulate set of components as C library

8. Status All features implemented
Alpha release at
Being used for TinyOS 2.x development work
Will be released with TinyOS 2.0

9. Backup

10. Generic Configurations
generic configuration SomeAssembly() {
provides interface X;
} implementation {
components new SomeAssemblyM() as SA,
new QueueC(TOSMsg, 10) as SomeQ;
X = SA.X;
SA.Queue -> SomeQ; }
Every instantiation of SomeAssembly will create new instances of SomeAssemblyM and IntQueueC

11. Generic Interfaces
Many interfaces similar, except for result, argument types
Generic interfaces support this by allowing interfaces to take type parameters
Two generic interfaces are connectable iff they have the same type arguments
Generic components with type arguments can use generic interfaces to:
Provide functionality dependent on that type
Express requirements of operations on that type

12. configuration MyApp { }
implementation {
components MyCode,
new QueueC(int, 10) as
MyQ;
MyCode.Queue -> MyQ; }
interface Queue<t> {
command void push(t x);
command t pop(); }
generic module QueueC
(typedef t, int n) {
provides interface Queue<t> as Q;
} implementation {
t q[n];
int p1, p2;
command void Q.push(t x) {
q[p1++] = x;
if (p1 == n) p1 = 0;
} …

13. Another example interface Compare<t> {
command bool lessthan(t x1, t x2); }
generic module Sort(typedef t) {
uses interface Compare<t> as C;
} implementation {
void f() {
t x1, x2; …
if (call C.lessthan(x1, x2)) …

14. Binary Components
component ExternalInterface {
provides interface StdControl;
uses interface Timer; }
entry points (of program including ExternalInterface):
ExternalInterface.Timer.fired
exit points:
ExternalInterface.StdControl.{init, start, stop}
ExternalInterface.Timer.{start, stop}

15. Attributes Information on attributes, etc output in XML
{ };
{ int key; }; …
provides interface
provides interface
Information on attributes, etc output in XML
Java-based parser for this XML schema
Sample “wiring check” demo app