Smaller than a Paperback

In this article, we'll focus on experimenting with Embedded Linux. We'll step through setting up EMJ's White Dwarf Linux on a Jumptec DIMM-PC system. The entire OS and applications will live on the DIMM-PC's onboard flash disk.

The DIMM-PC is a full-featured 486SX with 16MB of built-in IDE-compatible flash and 16MB of RAM, all smaller than a credit card. Also available are DIMM-IO modules that are the same size as the DIMM-PC but offer I/O capabilities such as Ethernet and VGA. We'll be using the DIMM-PC Combo module that provides I/O capabilities for Ethernet, VGA and two serial ports.

Figure 1. Jumptec's DIMM-PC and I/O Modules

I'll describe how to install a fully functional Linux system, complete with web server, on the DIMM-PC's onboard flash. We'll have a fully operational Linux system the size of a paperback, with VGA, Ethernet and no moving parts!

The DIMM-PC is tiny. However, the raw form has limited usefulness. You can't plug things like Ethernet, VGA and so on into the high-density cardedge of the DIMM-PC. You need a carrier board to expand the DIMM-PC's cardedge into useful real-world connectors like keyboard, mouse, IDE, VGA and so forth.

To get your DIMM-PC up and running easily, you will need the following items:

Observe proper Electrostatic Device (ESD) handling precautions with these sensitive components.

You will also need:

First, you will need a boot diskette and a root diskette. Images are available for download from the White Dwarf Linux page (see Resources).

Next, plug the DIMM-PC and the DIMM-PC Combo I/O modules into the proper slots on the evaluation board. Also plug in a keyboard, monitor, floppy drive and your Ethernet connection to the Internet. Plug power into the evaluation board and the floppy drive and power up.

When the system boots, the first thing you need to do is enter the BIOS setup and set the date and time. Without the proper date and time, some system functions and utilities may behave erratically. You need to do this every time the DIMM-PC is removed from its housing, as the battery needed for storing the BIOS settings is on the carrier board and not on the DIMM-PC itself. That means each time the DIMM-PC card is removed from the carrier board, the BIOS loses its settings.

Once the BIOS date and time are set and saved, place the boot disk into the floppy drive and reboot. You will see something like this in the messages that go by:

RAM disk driver initialized:
16 RAM disks of 8192K size
hda: SunDisk SDTB-128, ATA DISK drive
ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
hda: SunDisk SDTB-128, 15MB w/1kB Cache, CHS=490/2/32

You will then be prompted for the root disk. Once the root disk loads, the installer for White Dwarf Linux will run. Follow the onscreen instructions for setting up White Dwarf Linux and installing any optional packages, including a stripped-down Apache web server. Installing all available packages can take up to 50MB, so be choosy in what you select, since there are only 16MB of flash. You can add more software later.

Detailed information about the White Dwarf Linux installer and the specific packages is available at the EMT web site (see Resources).

When the installation is complete, remove the floppy disk from the drive and press the reset button. Your DIMM-PC should boot up. Log in and take a look around to make sure everything is working to your satisfaction.

You can leave the DIMM-PC as is at this point, but more likely, you'll want to transplant the DIMM-PC modules to something a little smaller than the large evaluation board. This is what the Mite PC-S board is for.

Figure 2.The Mite PC-S Carrier Board

The Mite PC-S carrier board holds the DIMM-PC, the DIMM-PC I/O module and provides connectors for everything except a floppy drive. This is why we need the main evaluation board--to boot from floppy to install White Dwarf Linux on the onboard flash disk. The DIMM-PC must be able to boot on its own before moving to the smaller Mite PC-S carrier board.

If the installation of White Dwarf Linux has gone well, shut down the system (use shutdown -h now) and power off. Then, remove the DIMM-PC and the DIMM-PC I/O cards from the evaluation board and insert them into the proper slots on the Mite PC-S board. Also plug in a monitor and keyboard and your Ethernet connection. You may also wish to add nylon standoffs to the Mite PC-S board or perhaps purchase the plastic enclosure specially made for the Mite PC-S (see Resources).