Carputer V1

ProjectsPublished February 26, 2010 at 12:00 am No Comments

This project was completed for kicks during the summer of 2007. It started out of from a want to create something useful that could handle music playback and prevent me from getting lost, as well as to help me learn more about Linux. It was marked as complete by fall of 2007. The writeup was completed as the project was ongoing, unlike many other items on the project pages where the write ups were done after the project was completed.

The system is composed of 4 main parts: a GPS receiver, a Nokia 770 internet tablet, a usb hub and a USB 2.5 inch hard drive. All of these parts were put into a 1991 BMW 318is.

By fall of 2007 the parts were removed and I had moved onto planning the second generation carputer.

background

At time that I am writing this document I am currently at the tail end of a rather full summer vacation. I still get a summer vacation because I am a still a student. I currently attend the FW Olin College of Engineering in Needham, Massachusetts and am a junior working on my ECE degree there. I am also the owner of a 1991 BMW 318is, a car that I love because of its light weight, m-tech suspension, retro looks and delightful driving dynamics.

In my current summer job, I have had the chance to work with some very basic embedded computers and have spent the hours in transit between work and home dreaming up a project that I could complete on my own that would implement the skills that I have now. Considering that I plan to drive across the country from Oregon to Massachusetts at the conclusion of this summer, I figured that a car computing project would be fitting.

Originally I had intended to make a mini-itx based system that used a low power Via-c7 processor mounted in the trunk. The display would be a 7-inch touch screen. Considering that just the processor, bare bones kit, and display would run me close to $600. I would expect the entire project cost me upwards of $750. While I could certainly afford such a project, it hardly seemed like a worthwhile cost when I all I wanted to do was to have a device that acted as a GPS and played music. Also, running wiring to the trunk and back again would not have been a pleasant task. Time was also an issue as I needed a project that could be completed in 3 hours a night over the course of a week. Thus, the idea of a simplified cheap system was born.

More than being cheap, however such a system would need to also be low power. Considering the age of my car, one can assume that the electrical system is not nearly as robust as the systems that go into new cars today. Back then the ABS computer, ECU , radio, CD changer and power door locks were the only things that needed to be powered. Also because I like the stock appearance of the car and because I want to keep everything more or less original there will be no cutting, no new radio, and the CD changer will still have to work.

To find an appropriate price target, I needed to make sure that anything I made would be substantially cheaper than anything currently on the market. A Tom Tom Go 910 does nearly everything I would want…and at a price point of just under $400 is an absolute steal for a commercially available solution. Therefore my initial pricing goal is $200, which incidentally is the cost of a bargain GPS receiver with a screen size between 3.5-4 inches. I will allow for incidental costs up to $250 which considering the capability of the system is still a relative bargain.

picking up the pieces

control unit/display

To make a project like this work, the first thing I needed to find was a control unit with all of the right characteristics. Initially my gut instinct told me to look at PDA’s, but I wanted to have at least a 4 inch screen to look at. So, most of them were not going to work; the ones that did work were at budget busting prices of at least $400. At this point I was about to head down to Fry’s and pick up a TomTom Go 910 at the bargain basement price of $389.99, when I spotted a refurbished DT375 thin client with an 8.4 inch touch screen for a meager $155.

While even this would likely blow my $200 price target, it wouldn’t blow away my $250 budget. After taking measurements I was slightly less elated. Measuring in at 8 inches by 9.5 inches, the unit was simply too big to fit nicely in my car. Along with unanswered questions about USB host capability, sunlight view-ability, and the availability of Bluetooth modules, the unit was looking like a no go. The unit also ran Windows CE…an operating system with little support and even fewer programs. So that DT375 while a hell of bargain wasn’t going to do it for me. Given more time and a car with a larger dash this might have been the ideal solution.

I was however very encouraged that thin clients were a solution that I had not thought of before, and therefore other solutions must exist as well. While frantically searching the web for a solution I stumbled upon the solution in the form of a Nokia 770 internet tablet. At $129 shipped from Buy.com (new in the retail box) this was a complete steal. With a sunlight viewable high resolution display, Bluetooth, wifi and a nice black finish, it was perfect.

Sporting a 4.3 inch touch-screen that seems bigger than the measurement indicates (due to a high res screen) and a compact form factor, the Nokia 770 also met the physical requirements. With a large community to support this product as a result of its open source OS (it runs a variant of Linux) mapping applications and media software is readily available. It is also a very low power product, meeting another one of my requirements. Sporting a dual core 252mhz TI 1710 OMAP processor, the internet tablet lacks a little bit of muscle but not enough to dissuade me from making it the center of my project. Furthermore as a contingency in the case that the project didn’t work out, I had an excellent new toy that I could use to access my other computers because of the fact that it has a built in VNC client.

gps unit

Well once the control unit was decided upon, it was time to buy a GPS receiver. Keeping budget in mind and wanting one of the latest SIRF III receivers I opted to purchase an OnCourse 3 Bluetooth receiver. It has WAAS and EGNOS integration and is pretty nice and small. Its rubberized black exterior also lacks the tacky looking silver plastic and super bright multicolor LCDs that other GPS receivers have.

At $49.00 shipped from buygpsnow.com, it was the cheapest option available. Unfortunately for me, I didn’t think this purchase through as well as I should have (considering the Nokia 770 find was still making my head spin) as this GPS receiver requires power (not solar) and doesn’t have the auto on feature that other receivers have, but it does have auto off. The irritating result is that I have to push the power button on the GPS unit to turn it on. Also if I didn’t plan on also using the GPS unit with my Moto Q as well, it would have been prudent to use a USB mouse style GPS as it would have always been powered when the system is on since the USB GPS receivers are bus powered. If I can find a USB GPS for cheap, somewhere in the future, I will make sure to be pick it up as it is more suited to a car system than a Bluetooth GPS receiver (a USB gps would have also saved me about $10 at the cost of not being able to use my phone as a GPS unit).

usb hub

If I had been willing to hack apart my Nokia 770 internet tablet, this would not have been necessary, but as they are, the Nokia internet tablets don’t support USB host capability out of the box. With a little parameter change in the OS and 5v dc supplied to the USB port they can do just fine. Alternatively you can hack in a power jumper between the power port and the USB (this also allows charging over USB) and then power devices without a hub. Since I am planning to run a fairly power hungry 60gb 2.5 inch hard drive off in this system, I figure getting a hub was well worth it. The trick was finding one that was easy to hack so that it provided 5v on the upstream line, something that is in violation of the USB spec. Wonderfully, enough no hacking is required if you buy a powered hub that violates USB spec out of the box. A little bit of searching allowed me to score the perfect hub on Newegg.com for a bargain basement price. The Anyware UH-204D usb hub has a nice aluminum enclosure. It also takes in 5v power and leaks that power on the upstream line. Again, there were ways that allowed me not to use the hub, but I figured with so many devices that use 5v dc to charge, it could be a power terminal as well as a feature that adds scalability to my project. Perfect!

data storage

I want music. Lots of music. For that reason, I needed at hard drive. Considering that I have a 67gb of music and a 30gb Ipod that was barely big enough for me to fit my favorite music on…I needed to have some serious data storage in my car. Since I was able to pick up a 60 GB hard drive for free since I already had it and a scored an enclosure off Newegg.com for 5.99+shipping (a Link Depot ENWB-25B-SS), it isn’t the best enclosure out there but it does the job.

wiring

Note that the GPS and the Phone will communicate data to the Nokia internet tablet via Bluetooth so they won’t need to be connected to power when their batteries are charged. Separate power will be used for the hub and for the internet tablet, because the charger on the internet tablet is a “smart” 5v charger that sends pulses up the line and also includes an IC to protect the battery from overcharging.

comprehensive parts list

Quanitity	Part	Source
1	Nokia 770 Internet Tablet	Nokia 770 Internet Tablet Purchase
1	OnCourse3 GPS Unit	Oncourse 3 GPS Unit Purchase
2	12v DC to 5v DC car charger	1 in Nokia 770 box, 1 in OnCourse 3   box
4	Mini USB link cable	various packages
1	USB Female to Female A	Fry’s
4	Male Terminal Disconnects	hardware store
4	Female Insulated Disconnects	hardware store
4	Crimp Connectors	hardware store
2	Insulated fuse holders	hardware store
1	Spool of 18 AWG Black wire	Radio Shack
1	Spool of 18 AWG Red wire	Radio Shack

system cost

Quantity	Part	Vendor	Price	Shipping	Cost
1	Nokia 770 Internet Tablet	buy.com	129.99	0	129.99
1	OnCourse 3 GPS	buygpsnow.com	49.99	0	49.99
1	USB hard drive enclosure	newegg.com	5.99	4.99	10.98
1	USB 2.0 powered hub	newegg.com	8.99	1.7	10.69
2	misc USB fittings	fry’s electronics	3.99	0	3.99
1	2.5 inch HD 60gb IDE	Overstock.com	24.99	0	24.99
Totals(USD)			223.94	6.69	230.63

The above price projection is for all of the parts needed to build my system. The cost of materials needed for installation doesnt count as part of my pricing goal because they would be needed even if I had bought a Tom Tom Go 910 and wanted to wire its power directly into my stereos wiring harness and not use the cigarette lighter for my system. Likewise, if I had elected to use the cigarette lighter for power, the additional parts would not have been needed.

total cost breakdown

Below is the cost to build and install same system that I built.

Quantity	Part	Vendor	Price	Shipping	Cost	Cost to  Me
1	Nokia 770 Internet Tablet	buy.com	129.99	0	129.99	129.99
1	OnCourse 3 GPS	buygpsnow.com	49.99	0	49.99	49.99
1	USB hard drive enclosure	newegg.com	5.99	4.99	10.98	10.98
1	USB 2.0 powered hub	newegg.com	8.99	1.7	10.69	10.69
2	misc USB fittings	fry’s electronics	3.99	0	3.99	3.99
1	10 Pack Male Disconnects		1.95	0	1.95	0
1	10 Pack Female  Disconnects		1.95	0	1.95	0
1	10 Pack Crimp Connectors		1.95	0	1.95	1.95
1	Wire (Red, Green, Black)		5.99	0	5.99	5.99
	Fuse Holders		0	0	0	0
1	2.5 inch HD 60gb IDE	Overstock.com	24.99	0	24.99	0
Totals(USD)			235.78	6.69	242.47	213.58

If there is an item that is marked as not having a cost to me, it means I had it on hand and thus did not count against my budget. The cost is the amount of money it would cost to replicate the system from scratch.

configuring the os and the software

Darkness and a lonely night made for a perfect time to play with my new little Linux machine. Certainly since this is not an out of the box solution, I need to change some settings and install a little bit of software.

the operating system

The Nokia 770 internet Tablet uses a build variant of the Debian distribution called Internet OS 2006 (or 2005 or 2007) which even though it was built in-house by Nokia was left as an open source OS. Nokia also offered it support to the independent developers that wanted to create applications for the internet tablets that they have made (N700, N770, N800). They called their software development platform Maemo. The open source nature of the SDKs for the internet tablets means that there is a dearth of applications available for this platform. It also means that this OS out of the box is a good option. I don’t need to install another OS. I don’t need to worry about Gentoo, XP Embedded, or Windows Mobile. Because of the nature of the community that is developing for this platform, many of the applications that I will be running are open source and thus are free (though donations are encouraged).

installing x-term

In order to make the OS more hack friendly I needed to install terminal, since no terminal was included to make the 770 internet tablet at least a slightly difficult to break the OS. The Maemo suggested X-Term emulator was downloaded and the packages installed. The installation files can be found here:

http://770.fs-security.com/xterm/

To use the internet tablet to its full potential, we need to be able to log in as root. Since there really is no easy way to do this in Internet Tablet OS 2006, I downloaded an application that forces root access on the 770. Called BecomeRoot, it is part of the OSSO-Xterm installation package. Just type in “sudo gainroot” to get root access.

Alternatively the guide below gives the same information with more help on how to install the packages in Linux.

http://examplified.net/guide/Nokia_770/Install_XTerm_and_Root_Access/

enabling usb host mode

To enable USB host mode not a whole lot needs be done. All that was done was to enter the following command into X-Term:

echo host > /sys/devices/platform/tahvo-usb/otg_mode

To turn the 770 internet tablet back to peripheral mode:

echo peripheral > /sys/devices/platform/tahvo-usb/otg_mode

That’s it.

maemo mapper

Installing this software is a breeze. It displays maps without any difficulty as long as there is an internet connection. This software worked wonders while my phone had high speed internet access even at 60 mph it had no problems pulling maps for me to use.

Once I got into low speed areas (anywhere outside major interstates and metro areas) it becomes unusable. Also the directions and voice features really do not stack up to the quality of the offerings available through a regular GPS. This software’s lack of features would be the major downfall for this system.

canola

While Canola was still in beta it was the best media player option available for my use since it was the only one out that is currently designed to be used without a stylus. I didn’t want to have to deal with using a stylus while in the car if I could help it so I went ahead and installed this very glitzy media player.

connecting the devices

bluetooth gps

This one is really easy. All you have to do is pair the device via Bluetooth and the Nokia 770 can just use it. Just like that.

usb hard disk

Once the hub was prepared and host mode enabled, all I had to do was to plug the drive in.

moto q smartphone

This is also really easy. Simple pair the phone as a Bluetooth device. The phone needs to have data access enabled as well as web access enabled. From there we can all surf the web with no issues. That is all the work that is needed.

improving the workability of the system

To make a better system, the powered USB hub would have to go. Also the Bluetooth devices would likewise have to go. Everything would be liked over USB and through an unpowered hub. Power would be supplied though a single 5v adapter. The GPS and the HD will always shut off when the GPS does and the 5v DC power converter would be removed from the system. This rework is fraught with risks. To make devices be able to run off of an unpowered hub, there would have had to jumper the power and the 5v on the USB (not an easy solder), also there could possibly be more than the 900mA of current getting pulled through the device. That high of a current pull that could either damage the device or the battery even though both should be able to withstand such a drain I am unwilling to risk my device (even though it was cheap) until I get a higher paying job or the internet tablet is out of warranty.

Perhaps in the summer of 2008 I will rework the system so I can have one integrated power bus. Such a change will lengthen the build but also help me get the cost of my homebrewed system under the $200 bar.

hitting the $200 price goal

Quantity Part Vendor Price Shipping Cost
1            Nokia 770 Internet Tablet  buy.com        129.99    0            129.99
1            USB GPS                          geeks.com     28.00     0            28.00
1            USB hard drive enclosure   newegg.com    5.99      4.99       10.98
1            USB 2.0 hub-unpowered    newegg.com    1.49      0.97        2.36
0            misc USB fittings               fry’s               0          0            0
1            2.5 inch HD 60gb IDE        overstock.com 24.99    0            24.99
Totals(USD)                                                        190.46  5.96        196.32

This pricing chart also reflects the changes specified in the “improving the workability of the system” section. That’s right…a cheaper and better version is possible, though at this point it’s all theoretical and I put none of it to practice.

the eplilogue

At the end of the project, Maemo Mapper simply isn’t good enough. I tried the Nokia Maps application and was likewise disappointed. It is worth noting that the Nokia Maps application didn’t work out because it was slow. So slow and system intensive on the 770 that you simply could not use both it and Canola at the same time.

Canola also had problems. It takes forever to index 60gbs of music. And it basically locks up the tablet while it is parsing. I would not recommend more than 4gbs of music for this reason. The sound quality out of the 770 is better than anything you can get out of an ipod but certainly not as good as you can get out of a high end Sony Walkman (in fact not even close).

In the end I abandoned this project and elected to build a regular car PC using a Mini ITX board running Windows XP. See the Carputer 2.0 page for more information and a similarly detailed write-up.