Definitions and background

Peripheral components:

• DMA controller
• fopur 10-bit ADC inputs
• serial ports (RS232, SPI, I2C, SIO)
• 42 multiplexed general purpose I/O pins

The communication subsystem is connected to the processing subsystem through a SPI interface

• The communication subsystem is connected to the processing subsystem through a SPI interface

• CC2420 RF transceiver
• when an RF message has been successfully received, the SPI interface enables the radio to wake up a sleeping processor
• the processor subsystem controls the communication subsystem by either turning it off or putting it in sleep mode

Designed for a specific application, namely, to monitor pig production

• Designed for a specific application, namely, to monitor pig production

• Motivation:

• monitors movements of a sow to predict onset of estrus
• so that appropriate care can be given for pregnant sows
• detecting cough or limping to monitor illness

The processing subsystems consists of :

• The processing subsystems consists of :

• microcontroller
• performs less complex, less energy intensive tasks
• initializes the FPGA and functions as an external timer and an ADC converter to it
• Field Programmable Gate Array
• executes the sow monitoring application
• coordinates the functions of the sensor node

There are a number of interfaces supported by the processing subsystem, including

• There are a number of interfaces supported by the processing subsystem, including

• the I2C interface for the sensing subsystem
• the SPI interface for the communication subsystem
• the JTAG interface for in-system programmability and debugging
• the serial (RS232) interface for interaction with a PC

Functional Aspects

• Functional Aspects

• Data Types
• Scheduling
• Stacks
• System Calls
• Handling Interrupts
• Multithreading
• Thread-based vs. Event-based Programming
• Memory Allocation

• Non-Functional Aspects

• Separation of Concern
• System Overhead
• Portability
• Dynamic Reprogramming

• Prototypes

• TinyOS
• SOS
• Contiki
• LiteOS

• Evaluation

An operating System is

• An operating System is

• a thin software layer
• resides between the hardware and the application layer
• provides basic programming abstractions to application developers

• Its main task is to enable applications to interact with hardware resources

Operating systems are classified as: single-task/multitasking and single-user/multiuser operating systems

• Operating systems are classified as: single-task/multitasking and single-user/multiuser operating systems

• multi-tasking OS - the overhead of concurrent processing because of the limited resources
• single task OS - tasks should have a short duration

• The choice of a particular OS depends on several factors; typically functional and non-functional aspects

Functional Aspects

• Functional Aspects

• Data Types
• Scheduling
• Stacks
• System Calls
• Handling Interrupts
• Multithreading
• Thread-based vs. Event-based Programming
• Memory Allocation

• Non-Functional Aspects

• Separation of Concern
• System Overhead
• Portability
• Dynamic Reprogramming

• Prototypes

• TinyOS
• SOS
• Contiki
• LiteOS

• Evaluation

Interactions between the different subsystems take place through:

• Interactions between the different subsystems take place through:

• well-formulated protocols
• data types

• Complex data types have strong expression power but consume resources - struct and enum

• Simple data types are resource efficient but have limited expression capability - C programming language

Two scheduling mechanisms:

• Two scheduling mechanisms:

• queuing-based scheduling
• FIFO - the simplest and has minimum system overhead, but treats tasks unfairly
• sorted queue - e.g., shortest job first (SJF) - incurs system overhead (to estimate execution duration)
• round-robin scheduling
• a time sharing scheduling technique
• several tasks can be processed concurrently

Regardless of how tasks are executed, a scheduler can be either

•