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System Architecture Overview

The Mobile Development Platform

This topic describes the two major components of the Mobile Development Platform: the BlackDog device, and the host PC. This information is intended to help you better understand the Mobile Development Platform so you can better design applications to optimally run on or against it.

Major Components

The Mobile Development Platform consists of two major components:

• BlackDog Device. A mobile computer, smaller than a cell phone, that users plug into the USB port of a host PC computer (running Windows XP or Linux) to develop and run applications using the host's peripherals. Developers can create applications that run directly on the device or that access applications over the host computer's network or Internet connection.
• Host PC. Users insert the BlackDog into the USB port of any host PC running Windows XP SP2 or Linux (Debian, RedHat, or SUSE.) The BlackDog projects X11-based applications on the host PC's display. Users communicate with applications running on the BlackDog using the host PC's monitor, keyboard and mouse; developers can also communicate with the device via ssh (assuming the host has an ssh server.) The BlackDog uses the host's TCP/IP connection to establish communications with external networks.

BlackDog

The BlackDog is a mobile, platform-independent, USB-powered computing device that fits in the palm of your hand. Users plug the BlackDog into a computer USB port to run applications directly on the device, or to access remote applications and services anywhere there is a network connection.  The BlackDog consists of an embedded Debian-based Linux operating system with up to 64MB of RAM, a PowerPC processor, and from 256MB to 1GB of flash. The BlackDog also includes a fingerprint scanner, accessible to users through the BlackDog casework. See BlackDog Specifications for detailed hardware and software information.

Note: The fingerprint scanner and authentication screens are provided only as sample applications for which developers can create an actual implementation.

The primary functions of the BlackDog are to:

• Store the user's personal computing environment, including data, preferences and personal applications, and development projects.
• Run applications, either directly on the device, or remotely using a client or browser.
• Allow a user to transport and run applications between different host PCs.

Characteristics of the BlackDog include:

• Remote GUI. Although capable of running local and remote applications, the BlackDog device has no application display window. Instead, it uses X11 windowing on the host PC to project the UI for sample BlackDog applications (and your own). Developers and end users interact with the BlackDog X applications using the monitor, keyboard, and mouse attached to the host PC.
• Host-to-BlackDog Communications. If the host PC has an ssh server, developers can communicate with the BlackDog via ssh. To facilitate application development, this connection is completely unsecure (allowing root access without a password).
• BlackDog-to-Host Communications. The BlackDog communicates with the host PC via the USB connection (TCP/IP network). To create a secure infrastructure, the only direct network connection from the BlackDog is to the host PC. Using network drivers, the BlackDog alternately presents itself to the host PC as either a:
  • CD-ROM device, to load bootstrap and host management software
  • Network device, to communicate directly to the host PC
• External Communications through Host PC. All BlackDog network communications are routed through the host PC, which uses Network Address Translation (NAT) to communicate with external networks in behalf of the BlackDog. The BlackDog never communicates directly with external networks.
• Power. The BlackDog draws power from the USB port on the host PC. A 3.6 volt battery on the BlackDog device supplies power for a real-time clock, and for a clean shutdown when the BlackDog is removed from the host PC.

Host PC

The host PC can be a computer running Windows XP with Service Pack 2, or many Intel X86 Linux operating systems, with a USB port, monitor, keyboard and mouse.

The host PC provides the following for the BlackDog:

• USB Power. The host USB port supplies 5 volts of power to the BlackDog device when it is docked on the host.
• X11 Projected GUI. Using X11 windowing on the host PC, the host monitor displays applications that are running locally on the BlackDog device or remotely. BlackDog users employ the host PC's monitor, keyboard, and mouse to interact with these applications. Out of the box, the BlackDog includes an application launcher that displays when users insert the device into a host PC and includes several sample applications (such as Xterm, games and so forth).
• Internet Connection. The host PC provides a TCP/IP Internet connection that the BlackDog can utilize.
• BlackDog-Host-External Network Communications. The BlackDog can communicate over all external networks available to the host PC. The host PC uses Network Address Translation (NAT) to translate all external requests originating from the BlackDog into the host PC's IP address before it forwards them to an external network.

Summary

With a BlackDog and access to a host PC, developers have a complete Linux development platform that allows them to carry, access and run applications from any location.

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