1. A Quick Note on TinyOS Chris Merlin Group Meeting January 21st, 2009

2. Outline • TinyOS: What Is It? • TOSSIM, The TinyOS Simulator • Dynamic Memory Allocation in TinyOS • Concluding Remarks TinyOS: What is it? TOSSIM, the TinyOS Simulator Dynamic Memory Allocation in TinyOS

3. TinyOS: A Quick Reminder • A Simple and stripped down operating system for motes • nesC language • C Based • For component-based programming • Maybe a quarter million programmers in the world TinyOS: What is it? TOSSIM, the TinyOS Simulator Dynamic Memory Allocation in TinyOS

4. (…2) TinyOS: A Quick Reminder • Components: black boxes whose input and output functions are known (interfaces) • Configurations: • assemble other components together • link interfaces used by components to providers • Modules: • Provide application code • Use and provide interfaces TinyOS: What is it? TOSSIM, the TinyOS Simulator Dynamic Memory Allocation in TinyOS

5. (…3) TinyOS: A Quick Reminder • Consider a module called Application that needs to turn LEDs on and off • The Leds interface provides functions to turn on/off, initialize, toggle LEDs • Application would like to use that interface • LedsC is a component that provides Leds interface • Application.Leds -> LedsC.Leds; TinyOS: What is it? TOSSIM, the TinyOS Simulator Dynamic Memory Allocation in TinyOS

6. Outline • TinyOS: What Is It? • TOSSIM, The TinyOS Simulator • Dynamic Memory Allocation in TinyOS • Concluding Remarks TinyOS: What is it? TOSSIM, the TinyOS Simulator Dynamic Memory Allocation in TinyOS

7. TOSSIM: Generalities • Simulator: • Built with make pc • Runs with DBG=[name], build/pc/main.exe [options] • What it does: • Displays traces • Emulates mote+radio behavior • What it doesn’t do: • Model radio propagation • Model power drain / energy consumption TinyOS: What is it? TOSSIM, the TinyOS Simulator Dynamic Memory Allocation in TinyOS

8. Compiling and Running a Simulation • Execute: build/pc/main.exe [options] num_nodes -b=<sec>: time over which motes boot -l=<scale>: runs sim. at <scale> times real time -r=<radio>: radio model: simple, static, lossy -rf=<file>: input file for lossy model -t=<time>: runs sim. for <time> virtual seconds num_nodes: number of nodes TinyOS: What is it? TOSSIM, the TinyOS Simulator Dynamic Memory Allocation in TinyOS

9. The Lossy Radio Model • Input file can specify links’ bit error rates • Lossy radio model can help create multi-hop networks of nodes • <mote ID>:<mote ID>:ber 1 1 1 0 0 1 1 TinyOS: What is it? TOSSIM, the TinyOS Simulator Dynamic Memory Allocation in TinyOS

10. Outline • TinyOS: What Is It? • TOSSIM, The TinyOS Simulator • Dynamic Memory Allocation in TinyOS • Concluding Remarks TinyOS: What is it? TOSSIM, the TinyOS Simulator Dynamic Memory Allocation in TinyOS

11. Dynamic Memory Allocation • “TinyOS does not allow dynamic memory allocation” • True: malloc will occasionally crash, realloc not supported on real motes • False: malloc, realloc, free all work fine in TOSSIM. MemAlloc provides some DMA for real motes TinyOS: What is it? TOSSIM, the TinyOS Simulator Dynamic Memory Allocation in TinyOS

12. Memory Model of TinyOS • Simplicity of TinyOS allows only static mem. alloc (no management of dynamic heap) • malloc must find space of appropriate size: can be resource consuming, esp. when mem. very fragmented TinyOS: What is it? TOSSIM, the TinyOS Simulator Dynamic Memory Allocation in TinyOS

13. MemAlloc • MemAlloc is provided by TinyAlloc • Some commands are: • allocate(HandlePtr hptr, int size): allocate memory region of size • reallocate(Handle h, int size) • free(Handle h) • However, MemAlloc is split-phase • Events: • allocComplete(HandlePtr hptr, result_t outcome): indicate an allocation has completed • reallocComplete(Handle h, result_t outcome) TinyOS: What is it? TOSSIM, the TinyOS Simulator Dynamic Memory Allocation in TinyOS

14. MemAlloc Example • TinyAlloc implements managed heap: simple array of handles • Memory regions are referenced indirectly by another array • Double dereferencing is needed Handle array; call MemAlloc.allocate(&array, 2*sizeof(ArrayEntry)); ArrayEntry *entry = (ArrayEntry*)(*array+sizeof(ArrayEntry)) TinyOS: What is it? TOSSIM, the TinyOS Simulator Dynamic Memory Allocation in TinyOS

15. Outline • TinyOS: What Is It? • TOSSIM, The TinyOS Simulator • Dynamic Memory Allocation in TinyOS • Concluding Remarks TinyOS: What is it? TOSSIM, the TinyOS Simulator Dynamic Memory Allocation in TinyOS

16. Remarks • If you have suggestions, pieces of code to add, let me know • Compiled in Tutorial on WCNG website / my Academic page