22-05-2012, 03:57 PM
Networked Embedded Systems
[attachment=22748]
Importance of Networked Embedded Systems:
Computer processors are increasingly embedded into everyday objects and become invisible.
More and more objects are networked – an “Internet of things” is evolving.
Sensors serve as an important interface: they link the real world to the virtual one.
Completely new applications arise.
Maximal Data Rate
Shannon –Hartley law (1948):
a channel with a bandwidth of H Hz and random noise;
maximum bps (bits per second) is: H log2 (1+S/N)
S/N: signal power to noise power (dB: 10 log10 (S/N) )
Current coding techniques approaches the limit
To achieve higher speed:
better cables and electronics
higher bandwidth (less attenuation of higher frequencies)
lower internal noise
decrease influence of external EM radiation
light via fiber optics
Advantages: simplicity
If any one device needs response in limited time, the system may don't work.
Respond slowly
This architecture is fragile to change
Because of these shortcomings, a round-robin architecture is probably suitable only for very simple devices.
Solution: Round Robin with Interrupt Architecture?
Function-Queue-Scheduling Architecture
In this architecture, the interrupt routines add function pointers to a queue of function pointers for the main function to call.
The main routine just reads pointers from the queue and calls the functions.
It can call them based on any priority scheme that suits your purposes. Any task code functions that need quicker response can be executed earlier.
[attachment=22748]
Importance of Networked Embedded Systems:
Computer processors are increasingly embedded into everyday objects and become invisible.
More and more objects are networked – an “Internet of things” is evolving.
Sensors serve as an important interface: they link the real world to the virtual one.
Completely new applications arise.
Maximal Data Rate
Shannon –Hartley law (1948):
a channel with a bandwidth of H Hz and random noise;
maximum bps (bits per second) is: H log2 (1+S/N)
S/N: signal power to noise power (dB: 10 log10 (S/N) )
Current coding techniques approaches the limit
To achieve higher speed:
better cables and electronics
higher bandwidth (less attenuation of higher frequencies)
lower internal noise
decrease influence of external EM radiation
light via fiber optics
Advantages: simplicity
If any one device needs response in limited time, the system may don't work.
Respond slowly
This architecture is fragile to change
Because of these shortcomings, a round-robin architecture is probably suitable only for very simple devices.
Solution: Round Robin with Interrupt Architecture?
Function-Queue-Scheduling Architecture
In this architecture, the interrupt routines add function pointers to a queue of function pointers for the main function to call.
The main routine just reads pointers from the queue and calls the functions.
It can call them based on any priority scheme that suits your purposes. Any task code functions that need quicker response can be executed earlier.