User guide

13.3.1 Community development model

It should be stressed that the IP04 is a community effort, with many people contributing. In no

particular order: the Astfin

& BlackfinOne teams, uClinux

, Analog Devices Blackfin team, the

Asterisk community, and Atcom.

13.4 IP04 Design

This section provides technical details of how the IP04

hardware and software works.

When power is applied, the Blackfin boot ROM starts

reading from the 256k SPI flash chip. The program it

loads is called u-boot, a powerful boot loader that has

been ported to the Blackfin by the Analog Devices

Blackfin team. U-boot has a command line interface

that lets you load other programs from flash or via

Ethernet. In normal operation it automatically loads

and executes the uClinux kernel.

A 256M NAND flash chips is used as the main storage

for the IP04. NAND flash has the advantage of high

density and low cost. It's the same hardware that is

used in your MP3 player, so prices have plummeted

over recent years. However the Blackfin boot ROM

can't read the NAND flash directly, which is why we

need the SPI flash chip and u-boot to support the start

up process. Compared to many embedded Linux systems, the IP04 requires quite a lot of flash storage

(around 16M minimum) to store the Asterisk executable and audio prompts.

After booting the kernel runs out of SDRAM, and the NAND flash is mapped to the root filesystem. We

also use a portion of the SDRAM for temporary files, e.g. /tmp.

The IP04 runs Asterisk and the uClinux operating system. Asterisk was relatively easy to port to the

Blackfin, thanks to the similarities of uClinux to the Linux operating system, and the maturity of the

Blackfin gcc toolchain. The Astfin

build system is used - a system of nested Makefiles and patches

that simplifies the complex build process required for the IP04.

56. Astfin http://astfin.org

57. uClinux http://blackfin.uclinux.org

58. Astfin, http://astfin.org/

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