Embedded Systems Programming, Networking for embedded systems, Prof. Shankar (16), Study notes of Embedded Systems Programming

Download Embedded Systems Programming, Networking for embedded systems, Prof. Shankar (16) and more Study notes Embedded Systems Programming in PDF only on Docsity!

Networking for Embedded

Systems

 Why we use networks.

 Network abstractions.

 Example networks.

Network elements

PE

PE

PE

network

communication link

distributed computing platform:

PEs may be CPUs or ASICs.

Why distributed?

 Higher performance at lower cost.

 Physically distributed activities---time

constants may not allow transmission

to central site.

 Improved debugging---use one CPU in

network to debug others.

 May buy subsystems that have

embedded processors.

Network abstractions

 International Standards Organization

(ISO) developed the Open Systems

Interconnection (OSI) model to

describe networks:

 7-layer model.

 Provides a standard way to classify

network components and operations.

OSI layers

 Physical: connectors, bit formats, etc.

 Data link: error detection and control

across a single link (single hop).

 Network: end-to-end multi-hop data

communication.

 Transport: provides connections; may

optimize network resources.

OSI layers, cont’d.

 Session: services for end-user

applications: data grouping,

checkpointing, etc.

 Presentation: data formats,

transformation services.

 Application: interface between

network and end-user programs.

Point-to-point networks

 One source, one or more

destinations, no data switching

(serial port):

PE 1 PE 2 PE 3

link 1 (^) link 2

Bus networks

 Common physical connection:

PE 1 PE 2 PE 3 PE 4

header address data ECC packet format

Crossbar

• in1 in2 in3 in - out - out
  • out
  • out

Crossbar characteristics

 Non-blocking.

 Can handle arbitrary multi-cast

combinations.

 Size proportional to n^2.

Message-based programming

 Transport layer provides message-

based programming interface:

send_msg(adrs,data1);

 Data must be broken into packets at

source, reassembled at destination.

 Data-push programming: make things

happen in network based on data

transfers.

I^2 C bus

 Designed for low-cost, medium data

rate applications.

 Characteristics:

 serial;

 multiple-master;

 fixed-priority arbitration.

 Several microcontrollers come with

built-in I^2 C controllers.

I^2 C data format

SCL

SDL

start MSB

ack

I^2 C electrical interface

SDL

 Open collector interface: +

SCL