Q Solutions

Embedded Internet

Overview

The Tcp/ip stack is implemented in the ansi C language. It uses macros to abstract the physical environment from the logical operations. This allows the code to be efficient yet customisable to a diverse range of hardware. It compiles with a large range of commercial and open source compilers.

Core Features

Protocols

• Arp
• Icmp
• Ip
• Udp
• Tcp
• ppp

Protocol Modules

• bootp
• dhcp
• dns
• http
• ftp
• telnet
• ssl/tls

Api

The user software communicates with the stack via the BSD standard calls. This allows the software to be developed largely on any compatible system and then transferred and tested on the embedded system without modification.

Api Calls implemented are:

• socket
• bind
• connect
• accept
• listen
• recv
• send
• sendto
• recvfrom
• getpeername

The following are dependant on the target operating system:

• open
• close
• read
• write
• select

The following are dependant on having libc integration:

• fread
• fwrite
• fprintf
• fscanf

Statistics

The stack keeps statistics on the network interface as well as upper protocols so that interactive debugging can be done on the stack in real time.

Network Interface

The stack can be interfaced to most standard ethernet controller chips. Data is transferred by either DMA, IRQ, or polled in an event loop.

All handling of the NIC is done inside the stack so that the application programmer never needs to interact with the hardware interface at any time.

OS host interface

The host can either call the stack in a loop and as such the stack does not require and operating system to function, the host software must provide routines to facilitate the following:

• Timer Tick.
  The tcp stack needs to know how long has elapsed since the last call.
• Memory allocation
  If configured for dynamic memory allocation, the host os must have the interface routines malloc and free

When advanced operation is required , some or all of the following features need to be provided to the stack

• Interrupt
  In most cases the OS must provide an interrupt handler callback in C for the Network interface chip.
• DMA Transfer
  The stack does not interface directly with the CPU resources to prevent a conflict with the application programs. The OS must provide a routine that starts DMA transfer on behalf of the stack.
• Semaphore
  In a multithreading environment the stack requires that tasks can be request sole access to the stack data structures for short periods of time.