I have completed my construction of a general-purpose 12-volt computer to use as a navigation computer in my RV (I intend to use Garmin Mobile PC) and also for amateur radio field use. In building the computer, I had to address a range of issues, and posting those here might help others who will be doing the same searches I did.
Enclosure
I'm using a Morex 3777 enclosure. I have replaced the power supply (see below). The enclosure did not come with enough screws for everything, and I had to dig around to find what I needed, particularly the tiny screws used on the slim CD drive tray. The drive tray will hold either a 3.5" HDD or a 2.5" notebook HDD, and I used the latter. The case comes with an IDE interface cable with a single device plug, and I needed a cable with two plugs, so I had to scrounge again. The case is too tight, though, for typical aftermarket non-ribbon IDE cables, unless one cuts off the rubber boots from around the plugs. I used a ribbon cable with the usual requirements for clever origami. Note that the case has laser-cut ventilation slots in an extruded aluminum enclosure into which the chassis slides. The ventilations lots have sharp edges. IDE and power cables tend to rub on the inside of the case and need to be protected from those sharp edges.
The case included a very quiet system fan.
Operating Systems
My system provides multiple boot capabilities. I have an XP SP2 partition, an Ubuntu Linux partition, and the ability to boot as an MS-DOS box using a compact-flash adapter (see below).
Ubuntu Linux version 8.04 has a problem with the Realtek LAN adapter on the mobo, which some have resolved by turning off the LAN adapter in the BIOS setup and using an external PCI card. This was an unacceptable solution for me. Ubuntu 8.04.1 resolves this issue, along with flashing the BIOS with version 099. The new BIOS is available here:
http://downloadcenter.intel.com/filt...9&submit=Go%21
And Intel has recently acknowledged the problem and also reported the solution of moving to the newer version of Ubuntu, here:
http://www.intel.com/support/motherb.../CS-029475.htm
These two things resolved the LAN issue completely, without the need for installing new LAN drivers. The LAN adapter worked out of the box with Windows XP.
Getting Ubuntu to recognize all devices proved a bit challenging. I had to configure the IDE flash adapter as a secondary device on the IDE chain using the middle plug on the IDE cable, reserving the end plug for the CD/DVD driver, which was not configurable for master or slave with the slim-drive adapter that came with the enclosure. I have the BIOS configured to boot from CD first, then HDD, then the CF adapter, using automatic sensing. I also set the BIOS to "natural" SATA and IDE disk operation.
Windows XP had no trouble recognizing all the devices, and was much less picky about the IDE setup.
I used the "CD5.sys" driver for the AOpen CD/DVD drive for operation in MSDOS. This driver is available here:
http://oldfiles.org.uk/powerload/msdos.htm
The "CDROM.EXE" file is the one to download, and it includes five generic .sys files for various brands. CD5.sys is the one that worked with my AOpen CD/DVD drive (I have not, and don't intend to, tested DVD operation under MSDOS). CD1.sys worked with an older Mitsumi CD reader. Once I had configured the CD drive and the CD/DVD drive on the IDE chain to make Ubuntu happy, MSDOS was also happy.
I could find no easy way to get MS-DOS to interface to the SATA hard disk, but I didn't really need to do that.
I installed MSDOS using a CD iso file that I downloaded here:
http://www.bootdisk.com/bootdisk.htm
I then formatted the Lexar CF card with FAT16, using the /s parameter to install the system boot files.
I'm using the GRUB boot loader that comes with Ubuntu Linux. I modified the menu.lst file used by GRUB to allow booting from the CF card as an option. On power up, I can therefore choose between booting XP (the default) from the first partition, Ubuntu from the second partition, or MSDOS from the CF card. GRUB is a much more flexible multiple boot load than the bootloader that comes with XP. But it requires installing XP first, then Ubuntu Linux, to keep from having to fight battles that are beyond my skills.
Monitors
First, for the 800x480 issue, this has been resolved in Version 099 of the BIOS, which is available from Intel. I was able to flash the BIOS without difficulty using the resources supplied here:
http://downloadcenter.intel.com/filt...9&submit=Go%21
I am using the 10-inch touchscreen monitor provided by Gooddeals18.com. I used the drivers available from here:
http://www.touchkit.com/Drivers.htm
These drivers worked, but I also had difficulty with the drivers supplied on CD with the panel.
I am powering the panel from the computer (see below), but it does come with its own power brick. I can confirm the rated power consumption for the monitor of less than 10 watts. I'm running the monitor at the native 800x600, but 1024x760 is also readable. Changing the resolution, though, requires recalibrating the touch screen.
I was unable to figure out how to install the touchscreen drivers for Linux, but I do not need that capability in Linux so I did not pursue it very far. I'm a Linux novice, and wanted the OS only to have access to some free applications. But it means keeping a mouse handy, or using a keyboard with an integrated trackpad. I also did not attempt to make the touchscreen work with MS-DOS, though drivers are available for touchscreens that use an RS-232 interface.
Power Supply
I am using the Mini-Box M2-ATX-HV power supply. I have provided a power cord hard-wired into the enclosure that uses Anderson Powerpoles to connect to a 12-volt source (I'm a radio amateur and have standardized on these connectors for my many 12-volt applications and devices). I am not (at present) using the ignition circuit source, and am thus using the PS as a conventional PS, not as a "smart" automotive PS. Mainly, I wanted the wide input voltage range, and the M2-ATX-HV will accept input voltages from 6-32 VDC.
I have also wired the case's coaxial power connector into the incoming 12-volt bus using two paralleled 3-amp rectifier diodes. This will allow me to plug in the power brick or another battery without disconnecting the main battery source, so that I can change batteries without interruption. The PS handles the voltage drop from the diodes easily, and the diodes prevent the main battery from attempting to feed current to the additional power source. Note that this is not intended to be a tank battery, which requires a charging feature.
I am powering the monitor using a 16-gauge zip cord that is wired to an HDD molex connector inside the case. That provides a regulated 12-volt source to the monitor.
Power Consumption
Here's the final tally of system hardware:
- Intel D945GCLF Little Falls motherboard, with 1GB ram
- Samsung 120GB SATA 2.5" HDD
- Addonics IDE CF card interface, mounted in a PCI card slot (but it does not use the PCI bus) with Lexar 1GB CF card (for booting MS-DOS)
- AOpen slim CD/DVD drive
- Mini-Box M2-ATX-HV power supply
- Morex 3777 enclosure (separate 4-pin Molex cable required for the Intel mobo; separate two-device IDE cable also required). The case includes one very quiet system fan.
- Gooddeals18.com 10" touchscreen monitor, with Touchkit drivers, powered from the M2-ATX power supply
The power consumption for these devices totals 35 watts, no matter what OS is being used. The CD drive might increase that by 2 or 3 watts when spinning at full speed (I did not do a write test), but in normal operation, its consumption is less than a watt. Without the P4 power cord in place, the power consumption is less than 20 watts, so much of the power is consumed by the Intel supplemental power bus for the processor. The two fans (one for the 945 chipset and one in the enclosure) draw less than a watt each. Power consumption was measured at the 12-volt source. This met my goal of having a computer that would run for over 24 hours on a large, deep-cycle battery.
Published tests notwithstanding, the computer provides quite decent performance.
Many of the problems I ran into were solved while I was building the computer, so hopefully this summary will provide help the next person who comes along. I may still be having some issues: The mobo seems to lose its real-time clock if left unplugged for very long, and the touchscreen needed recalibration on one occasion unexpectedly. I'll know more about these issues when I put the computer in actual service.
RickD