I'm hoping someone will figure this out too.
I wish I had the expertise to figure it out myself, but I am a civil engineer (that wishes he went into electrical engineering).
I was searching the web and found a site where someone was looking to do the same thing. They may even be one of our members.
Anyway, below is the info he had on the website. It probably says exactly what Jaak said previously in this post, but in simpler terms. :32:
How to replace a not so slick 7 segment LED display in one's Murano with a slick navigation computer.
Ok, I'm still not convinced it's going to be possible. Well, OK, anything is possible, but I'm still tackling the biggest issues which are below.
Questions
· How does one keep the existing display? I have a Sat kit installed, and I want to see what's playing. It would also be nice to see the maintenance notes and such.
· What type of computer is best for this job?
· If I install a computer in my car, then what other fun things can it do besides show me maps?
Features
· GPS navigation. What good would it be not to do this?
· Bluetooth handsfree. How cool would it be to have the display pop up caller id info and have a big old button to push to answer your phone? This one is trickier for me though, as I don't think I'll get all the fun bits like a mute function or playback through the speakers. Maybe, but I haven't thought that far ahead yet.
· MP3 player. Again, because I have a sat installed, I can't get one of the really cool PAC kits. There are other ways to do this though.
· Get online using a GPRS phone while driving. This is mostly for things like a weather update as you're traveling, or traffic maps. That sort of thing. No web surfing while the car is moving!
Those are some of the questions and interesting features (there will be more features). Below are some answers and details. Think of this page as a design and detail page. Software and images will be on other pages.
First, can I get keep the existing display? Well, it turns out that's a really tough question to answer. There are three data pathways going to the existing display. One is known, it's a CAN bus which is a generic network used in the auto industry because it's versatile, and good at having many dissimilar nodes that just relay info about themselves. I'm not too sure what information comes over the CAN bus at this time, but I suspect not knowing this won't keep me from doing the job. I'm assuming it's everything but climate control and radio data. A second bus seems to be an RS422 serial bus, but I'm still working on that. This bus comes off the climate control interface and supplies the all of the climate control details you see on the bottom of the display. Finally, the third bus kinda looks like a simple RS232 serial connection (but could be some offshoot of an I2C bus or somesuch). This is what provides the radio information to the display. Time is kept by the display itself, so I don't really care (you can get really accurate time from a GPS receiver). Making sure I have the radio and CC display is the big challenge. Without that, I lose a big portion of what I like about having the display. That, and I want to say I did it I guess. Nothing beats a good challenge. I'm getting a lot of useful advice about this from a couple of smart hardware guys too, so it's definitely feasible.
Hardware
Ok, lets say I get all that figured out. Then what? Well, time to hook up a computer. What kind? I've thought a lot about this, and have come to the conclusion that a big old carputer that you see on a bunch of different websites is overkill. I'm an embedded engineer by trade, and I like to keep things in perspective. This unit won't be playing games, movies, or doing any number crunching, so a CPU is really simple. It's gotta be low power and cool. Passive cooling only. The computer itself has to work in a very wide temp range. For these reasons, I've decided to use a single board computer (an SBC) designed to be embedded in more extreme environments. You can get these fairly cheap with a bunch of USB and serial ports for the variety of attachements one would need. They also run quite well off of 12V DC and usually require less than 10 A fully loaded. Plus, I get the ability to put the unit to sleep so it would then consume less than 200 milliwatts of power, hence not killing the battery. That's a big plus because you don't have to worry about booting it everytime. Instant on unless you disconnect from the battery. I've also decided not to use a real hard disk drive. Mostly because they require more power, and in a car, they are a very real potential source of failure. Instead, I'll drive this whole thing from a 1Gig compact flash card. Well, I hope, the maps may change that to a 2gig card, but I'm still working on the platform parts. The music can then come from a USB flash drive. Easy to change day to day, and those things can store a gig. Who is going to need more than a gig for a car trip?. When I finally settle on the specific board, I'll post it here, but the specs I'm working towards are the following.
· Ultra low voltage or low voltage pentium chip in the 400 to 700 Mhz range
· 256 Mb RAM
· 4 USB ports
· 4 serial ports (if I do have an RS422 bus in the car, then one of those ports has to do RS422)
· Compact flash slot
· PC/104 compatibility. This wold be for a CAN upgrade to listen to the CAN bus in the car
· Watchdog capability. If the system hangs, it would be tough to reboot. A watchdog can reset the system for you.
· Some sort of usable display capabilities (LVDS would be best). Several of the boards I'm looking at have an AGP bus.
· Roughly 6x4 inches big
The display will be chosen to replace the existing unit without dash modification (if possible) the existing 7 segment display. This is proving to be difficult. Most of the LCD displays out there are just a little too big height wise. I did find the perfect unit in terms of size, and it's resolution can't be beat (1024 x 600), and it turns out it's not too expensive, but I'm concerned about how it will look when the sun's shining on it. If anyone knows what display the NAV enabled Murano's use, then let me know, I can shop for that. Basically, I want this to look OEM if possible. It's also got to be a touchscreen obviously, as I have exactly no idea how to get at the little joystick in the console. When I finally choose the display, I'll post that here as well. Note that the exisinting display size is 177mm x 110mm. There is a little bit of room above and below, but almost none on the sides, so it's possible I could use one of the 6.4in displays which are roughly the same width, but about 15mm taller. That detail still needs working out.
Software
The platform will run Linux and QT embedded if I can get it to build. Since it's x86, I'm using slackware 10.1 as a base, and will trim it down quite a bit. I want to use QTE because it's slick, and I've got lots of QT programming experience for embedded platforms. But it's very hard to build the way I want it, so I'm having issues. XWindows takes too much resource wise, so that's really not an option. Microwindows (I think it's actually Nanowin now?) is a distinct possibility, and it's easy enough to build and get going, but I'm not sure about how to write for it, so that's really plan B. Because of how this is all setup, I don't have any swap on purpose, so memory usage is pretty crucial (hence not using X). Actually, plan A.5 might be Microwin with QT (no KDE, again, too bloated). We'll see, more to come on that later. GPS maps will come from one of the many map programs out there already. Just need to port it. The bluetooth handsfree hasn't been done yet that I'm aware of, but it shouldn't be too tough. I have a caller id app that lets you get messages from the phone, and I know people have gotten audio off the phone, so it's a matter of putting some pieces together. And how cool would it be if an SMS popped up on the screen without touching your phone? An MP3 player will be super simple with the 10,000 existing projects I can mooch off of. Nice thing here is that I can make it play any audio code I want to, so Ogg, FLAC, mp3, wav, whatever will work.
