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Hardware Hacking Displays

Making a Color LCD Dashboard Replacement? 132

Posted by Cliff from the not-as-reliable-as-the-gauge-but-cooler dept.
DarkHand asks: "I've recently begun a project that would allow me to replace the analog gauges in my cars dash with a TFT LCD screen displaying a digital representation of the same. A number of animated analog-looking gauges would display the same information the physical gauges display, based on info from the ECU, as well as any other information the ECU has access to, such as intake air and coolant temperatures, throttle position, pop-ups for any warnings or error codes, etc. I'm looking to be able to add, remove, and customize the positions of the individual gauges, and possibly even make the background skinnable. Stability is crucial, so I'm leaning toward a Linux-based system. I have a few software friends who are willing to help on that end, but finding the proper hardware for such a project has proven difficult."
"I need something that either boots within a few seconds, or draws very little power when idle so as to remain active and run off the cars battery. A laptop or small computer boots too slowly, and draws too much power to stay on all the time. A high powered PDA with a larger screen would be perfect, but as far as I know it's not possible (or at least not easily doable, both in hardware and software) to change out to a larger display. The best option I've found so far is the venerable Gumstix board, but as far as I can tell, LCD support is still shaky. Has a similar homebrew project been done before, where I could go for wisdom? What kind of hardware would the Slashdot crowd use in such a situation?"
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Making a Color LCD Dashboard Replacement? More

Making a Color LCD Dashboard Replacement?

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  • sounds dangerous (Score:2, Insightful)

    by p373 ( 689997 )
    I suggest getting a Toyota Prius if you want to drive a space ship. Check this picture [motortrend.com] out.

  • Legal issues (Score:3, Interesting)

    by afd8856 ( 700296 ) on Saturday February 05, 2005 @10:05AM (#11582113) Homepage
    Wouldn't this kind of things have to be certified first? I mean, I can imagine a scenario where the driver would say to the police: I didn't know I was going 120 /h, look, my gauge pnly says 20 :-)
    • It's also illegal to tamper with the odometer. If you ever sold the car, you would have to somehow prove that you didn't tamper with it, which is probably a lot harder than it sounds.
      • depends. it's not illegal to replace the meters.

        what is illegal is to lie about how much the car has been driven, of course.

      • On my previous car, the odometer broke at 85000 km...the mechanic was quite surprised that I ask for the new one to be set at the same value that the old one...
      • In most places, you can sell a car with an unknown milage on it. What you can't do is misrepresent the milage. If (for example) your odometer has 'rolled over', the mileage it reads is now incorrect. But that doesn't mean you can't sell the car.

        Of course it's going to be a lot harder to sell a car with unknown milage - but that's a different matter. Selling a car which has been severely 'hacked' is likely to be tricky anyway.

      • You wouldn't have to prove anything, but rather most of the time you do have to write the actual mileage on the title - or at least what the odometer says. Furthermore, it isn't illegal for the odometer to read incorrectly, but it is illegal to tamper with an odometer. In my last car, the odometer broke at around 270,000. I sure as hell wasn't going to invest in getting that fixed - at that point in it's life, 40,000 more miles wasn't really gonna make a difference.

        Now, if it was me, I'd see if I could

    • Re:Legal issues (Score:2, Informative)

      by DarkHand ( 608301 )
      I forgot to mention in the article that this would be for an autocross/track car, so legal issues aren't a problem. Sorry about that. :)
    • If your gauge is inaccurate, it won't get you out of a ticket. It may get you an equipment violation, but trust me, having an inaccurate or non-functional speedometer won't help (having changed rear-end gears, tires, and broken speedo cables before)...

      Normal auto gauges don't hold up in court, anyway. Unless you're driving a retired police car that says "certified" under the gauge, anyway. :)
  • You may want to check the refresh rate on the LCD you choose to use, as I remember reading that LCD tachometers were not common as the numbers changed way to fast for the refresh on the screen. Of course that was 5-10 years ago, so they may be of a much? faster refresh rate now.
    • i think 60fps is plenty enough for a refresh rate on a speedo, but what could be a slight problem is latency. LCDs have approx. 20ms latency which in critical situations could cause problems... of course the advantage of all this is that the computer can log the speeds etc VERY accurately and at a high rate so if the police question you, you can say 'actually'...

    • Re:Refresh rate.. (Score:3, Insightful)

      by Jerf ( 17166 )
      I think for that, I'd use a linear guage like a progress bar, which you can update as often as you like and let the LCD take care of blurring it "in hardware" (when life hands you lemons, make lemonade :-) ). The number can be a running average of the last second or so to stabalize the number, and with only slightly more cleverness you can ensure that if that number is flopping between two close numbers like "74" and "75" that you'll suppress that.

      (You may even be able to kill two birds with one stone here
      • Life critical information? Gauges are a luxury, at best. If my gauges broke tomorrow, I wouldn't stop driving. I would hope that most people can estimate their speed based on the sound of their engine. This is a lot easier, of course, to do when you have a manual transmission, as you always know what gear you're in. Still, for any driver, you should be able to at least ballpark it, especially when others are on the road.
        • Ah, a perfect illustration of what I mean.

          It's not just the literal information the guages are carrying. If you write something that is inadvertantly hard to read, and it takes you a second to puzzle it out, that's a second you're not looking at the road, which I'm sure you'll agree is a life critical issue. Certainly nobody can drive with their eyes on the road literally 100% of the time, but every moment you aren't looking at the road better have a direct and important payoff, and "puzzling out the meani
          • This is no different than how people react to the information on stock gauge clusters. "Why is that light blinking?" "What does the circle with two arcs around it it mean?" In fact, you have an opportunity to present the data in a better matter, something you know you'll understand. In the world of hand held cell phones, newspapers, cup holders, vanity mirrors, and in dash navigation systems with text displays, I hardly think the situation can be made any worse.
        • I think you're being a bit short-sighted. There are gauges on the dash that, while not life/death critical, are very important. What if the system crashed and you ran out of gas in the middle of nowhere? What if you weren't able to see that you had an oil leak and you ruined your engine.

          Also, you'd have to take a lot of non-obvious considerations when attempting a project like this. For instance, one huge advantage to physical gauges is their ability to be seen in any lighting condition with a simple o
          • Knowing some plane theory, I agree with the oil point. Also, a needle or progress bar (as stated on other message) would be better than the number, because you don't need to look directly at it to get an estimation. If you tried digital depth meters in a boat, you'll realize that the jumping number is harder to read than an analog representation.

    • Re:Refresh rate.. (Score:5, Informative)

      by WebCrapper ( 667046 ) on Saturday February 05, 2005 @04:14PM (#11584703)
      Actually, LCD's don't really have issues like that at the moment. Check out the Pioneer AVIC-N1. Its a DVD player that hooks into the vehicle and will display the gauges, just like the story parent wants. Its possible, just a matter of making it work from scratch.
    • Why use an LCD tach at all? It seems to me a better idea would be a row of LEDs along the top of the dash, shrouded from outside light - one for every 500 RPM would probably be sufficient for an automatic, or maybe one per 200 RPM for a manual. This would not only provide a solution with very low latency, but would also mean one less thing to display on the main screen, freeing up a goodly amount of space for the various things mentioned in the article.
      • That is what the original article I read has suggested..
        They'd had requests to publish plans for a kit LCD tacho, but instead used a line of ugly yellow, green and red leds..
        Now though, we could have a dizzying array of bright blue, green, white etc. Just enough to blind the driver! :)

  • Linux is NOT what you want (Score:5, Insightful)

    by nullset ( 39850 ) on Saturday February 05, 2005 @10:13AM (#11582156)
    what you want is an RTOS. Look around at various embedded sites, such as www.circuitcellar.com or www.embedded.com to find similar projects that us an RTOS or no OS at all.

    Do not for the love of God make your speedometer be a PC.

    --buddy
    • his not going to rely on _controlling_ the car on linux, just showing some variables.

      standard speedometers already suck by default, they are not that fast to respond, nor very reliable, and wouldn't really be that dangerous to be shown by a pc. they're already shown by a computer built on a shoestring budget anyhow(seperate from the systems that actually control things like abs brakes and stuff that _really_ matters).

      you can always stop you know if those meters stopped functioning, if you couldn't then yo

    • Free RTOS (Score:3, Informative)

      by EtherAlchemist ( 789180 )

      Free RTOS [freertos.org] has an open source RT kernel as well as some handy dandy how-tos and technical resources.

  • Comment removed based on user account deletion
    • You know that most F1 team budges are in the hundreds of millions, and sometimes a billion, dollars a year, right?

      They spend big money on that telemetry system!

      -psy
    • The steering wheel in a Formula 1 car is worth about $50K USD. That's just food for thought.

  • Safety Issues (Score:3, Funny)

    by TinheadNed ( 142620 ) on Saturday February 05, 2005 @10:53AM (#11582343) Homepage
    I don't think your car would be road-legal with a software speedometer. What you might be able to do is use an FPGA as that does not strictly count as software (sometimes). Use an FPGA and an LVDS driver chip and not much else, and you might be able to get away with it.

    If you don't know how to do that I would *seriously* reconsider your idea of replacing a piece of hardware that you trust with your LIFE.

    Let's be honest, you don't want your eulogy to be "Well, he wanted his car to play the Back To The Future music when he got to 88 mph."
    • just about every speedometer from 1996 (in the US at least) has been software controlled. they're not the old cable-attached-to-the-transmission type anymore. it's all speed sensors that go to the ecu that output a voltage to the speedometer. so there's nothing realy different with what the original poster wants to do. i don't see how it couldn't be legal.
      • There is a difference between software running on dedicated hardware such as a microcontroller, or an FPGA, and running a whole multi-tasking operating system.

        For one thing, the first method is designed for its job, whereas the OS is totally extraneous.

        Also, any software/firmware in the ECU of a vehicle will have undergone quite a lot of quality checking, code standardisation, and testing on dedicated hardware. I don't see many easy ways of testing the proposed modification to the car.

        I would have thoug
        • You can replace your engine management system with whatever you want. You can replace your gauges with whatever you want. You don't even need gauges to be road-legal, but you'll probably get busted for speeding more quickly if you don't have feedback on how fast you're going. The law requires a working odometer, but just so you don't misprepresent the mileage when selling. Once you go over 100K, odometer readings are ignored anyway.

          Aside from the speedometer, what gauges do you think mean jack squat to

          • You can replace your engine management system with whatever you want. You can replace your gauges with whatever you want. You don't even need gauges to be road-legal, but you'll probably get busted for speeding more quickly if you don't have feedback on how fast you're going. The law requires a working odometer, but just so you don't misprepresent the mileage when selling. Once you go over 100K, odometer readings are ignored anyway.

            Note that this might be true in the poster's area, but may vary. Right he

            • Re:Safety Issues (Score:3, Interesting)

              by cloudmaster ( 10662 )
              I drove a truck for about 1 year with no speedometer (because it broke). I didn't get pulled over once in that time frame - probably because I knew about what a safe speed was. I know people who've disconented their speedo for a while when they're planning to trade a car, so the odometer doesn't keep going up. :)

              I've been puilled over and tried to get out of it with a "I just put in new rear-end gears" (which was true - going from a 2.73:1 to 3.46:1 is a big jump), but I got the same ticket I would've go
              • I spent about a month back in the mid-90's with no speedo in my Fiero. I made a mistake removing the vehicle speed sensor. I thought the VSS unscrewed. It doesn't.
      • cough... 2000 ford taurus has a "mechanical" speedometer...
    • Software speedometers are used now in expensive cars like cadilacs.

      I think your confused on how all this works.

      I had a friend who had a broken cable speedometer for over two years. That to me seems more dangerous then a software speedometer.
    • Meh, the legality of it is moot. Things with a lot less testing are very much road legal. There are hundreds of unique kit car designs out there that get registered all over. The monkeys at the DMV probably wouldn't even care when they inspect it.
    • If you don't know how to do that I would *seriously* reconsider your idea of replacing a piece of hardware that you trust with your LIFE.

      I put more trust in my CB radio than my speedometer. The CB radio tells me when there's traffic suddenly slamming to a stop on the freeway ahead, I've yet to find a speedometer that'll do anything more than tell me how fast I'm going to hit whatever's stationary ahead of me.

  • OBD II (Score:4, Informative)

    by planetjay ( 630434 ) on Saturday February 05, 2005 @10:58AM (#11582360) Homepage
    I googled 'OBD II' a while back and found these:

    http://www.obd-2.com/ [obd-2.com]
    http://www.ghg.net/dharrison/obdscan.html [ghg.net]
    http://www.obdii.com/ubb/Forum1/HTML/000359.html [obdii.com]
    http://www.andywhittaker.com/ecu/obdii_software.ht m [andywhittaker.com]
    http://www.elmelectronics.com/obdindex.html [elmelectronics.com]
    http://www.dynahud.com/default.asp [dynahud.com]

    They should get you started...

  • Cold weather okay? (Score:5, Informative)

    by nsasch ( 827844 ) on Saturday February 05, 2005 @10:59AM (#11582368)
    Leaving a computer in the cold weather might also be a problem, and LCD's have a noticably slower refresh rate in the cold.
    • Leaving a computer in the cold weather might also be a problem, and LCD's have a noticably slower refresh rate in the cold.

      It's not JUST cold weather you have to watch out for... I've seen LCD's go completely black when they overheated... like from sitting out in the sun. Since car temps can easily get well over 100 F when left in the sun, this could be a real problem. Then there's the matter that the electronics you use need to be able to operate at those temps, too. You need to make sure you have a la

      • I'm in NE USA right now, and just this week the temperatures have been swinging quite a bit(cold still, but swinging) When LCD's go completely black, is it permanant, or just while still heated or for a short time(a day or less) after the condition?
        • Had that happen to my cell phone once when I forgot it in a car. It went black indeed, and the display was unreadable. It did go back to normal when it cooled down (took a few minutes) though.

          It only happened to me once though, so maybe the damage accumulates, or it'd have got permanently damaged if I left it there long enough
      • My old discman used to do this all the time, pretty much every day after school in the summer. I haven't seen one do it recently though, is it possible that newer lcds have a higher temperature tolerance? Or maybe a colored lcd doesn't because of different construction.

        Back to the point, in my case it was only temporary and would go away within a minute or so of the temperature dropping when I rolled down the windows. I guess it would depend on where he lives, color of his car etc.

      • I've seen LCD's go completely black when they overheated

        You can apparently get ones that have wider temp. ranges. Both of my vehicles have at least one LCD display and here in central MN, typical temperature variation is from the -20F we had last month, to the >95F we'll have in early August. Farther north, -50F is seen a few times each year. I'm guessing someone makes automotive temp. range spec'd LCD displays.

        When I first noticed that the odometer was an LCD display, I was concerned about it, but

  • Some of these (Score:5, Informative)

    by Apreche ( 239272 ) on Saturday February 05, 2005 @11:00AM (#11582370) Homepage Journal
    http://www.arcom.com/pc104-xscale-viper.htm

    Some of those thingies running embedded Linux might do the trick. Just attach it to the car's computer via USB or serial cable. It has its own LCD controller and can run embedded X windows even. Then writing the software is relatively simple.

  • Your question: (Score:3, Interesting)

    by BrokenHalo ( 565198 ) on Saturday February 05, 2005 @11:27AM (#11582513)
    where I could go for wisdom?

    Well, it strikes me that the obviously wisest choice here is to leave well enough alone. Mechanical components are so much more reliable, there's no comparison.

    Plus, I'm not sure what the regulations are in your country/state, but here in in Australia it is an offence to reset an odometer unless an engine has been replaced (in which case the vehicle has to pass an inspection by agents for the authorities). I'm pretty sure that kind of modification, where the gadget could be easily reset without trace would be illegal.

    I'm sure there must be more useful avenues to apply geeky talents.

    • Re:Your question: (Score:2, Interesting)

      by Tabor_Kelly ( 849807 )
      Plus, I'm not sure what the regulations are in your country/state, but here in in Australia it is an offence to reset an odometer unless an engine has been replaced (in which case the vehicle has to pass an inspection by agents for the authorities).

      And what if the odometer breaks? Thier are a ton of (German) cars on the road with 80's vintage VDO odometers that have stopped working. The only factory/VDO aproved way to fix them is to replace the whole speedometer unit. Where I live in the United States, th

    • For what it's worth most (well nearly all, actually) cars these days have electronic instruments. They are far from the mechanical linkages of of yesteryear. Even though they are analog guages, they are driven by a PWM signal on a wire.. The faster you go, the faster it pulses, the more voltage goes to the speedo.

      It would be pretty easy to read the values with a microcontroller and then feed them to a PC or directly drive an LCD/VFD text-type display via serial, but I agree with you -- what's the real poin
    • The engine controller also records the speed, and the mileage. It's not *just* recorded on the odometer (which is also digital on many cars).

      Plus, there haven't been any mechanical gauges in most cars for a decade.

      I'm sure there must be a more useful forum for you to post your misinformed opinions.

  • LCD? (Score:4, Interesting)

    by Cyclone66 ( 217347 ) on Saturday February 05, 2005 @11:39AM (#11582592) Homepage Journal
    You won't be able to see it in the sun, this is a bad idea...
    • "You won't be able to see it in the sun, this is a bad idea..."

      If that were so, then the screens used in airliners, fastjets, and helicopters wouldn't work either, and I seem to remember they spend a lot of their time above the cloud where it's always sunny.

      There must be some easy solution, just because aircraft seem to have worked-through the problems.

      • The LCDs used in aircraft [honeywellaes.com] are special units, with high contrast and much more powerful backlights than consumer LCDs. The conumer ones are mainly geared toward compactness, light weight, and low power consumption. The aviation displays end up being much bulkier and power-hungry (though still lighter than CRTs.)

        If you could acquire such a panel, then you might be on to something.
  • that sounds like a fun project. you're probably right that an lcd (while hard to read in the sun) is probably the most versitile way to display all the gauges and dtc's and everything, you might also want to consider going analog. i'm in the middle of a project on my old '89 toyota which predated obd-ii. but i still can get a bunch of information from the outputs of the ecu. i don't have the cool obd-ii plug that you'll have access to, so i need to splice in the actual wires coming out of the ecu, but t

  • Paperback-sized computer (Score:3, Informative)

    by RyMon ( 547040 ) on Saturday February 05, 2005 @12:05PM (#11582762) Homepage
    You might consider one of these [norhtec.com]

    From the site:
    SIS 55x processor (x86 compatible)
    3 USB ports
    2 Serial (RS-232) / 1 Parallel port
    Built in AC97 audio - Audio in/out
    2 VGA out ports
    ATA-33/66/100 support
    1 or 2 RJ45 for 10/100 MBit Lan
    PS/2 Keyboard/Mouse connector

    Single 5 Volts DC @ 1.8 A support

    128 MB RAM
    20 GB 2.5" hard disk

    1 NTSC or PAL video in (frame grabber)
    1 NTSC or PAL TV out
    Support for two VGA displays

    I've been looking at doing a project like this for a while now, so I'd be interested to see how you go about some things.
  • Like in John Carmack Testarossa, why don't you just manage to wire a plug on the dashboard to connect your laptop when you are bored ? Then you can have all the information you want, without making your car too illegal at first look. On the top side, you could change motor management "on the fly", when you want performance or economy, etc...A friend of mine is modifying previous models for export to Iran, where the fuel is of low quality, and test-drives the car this way. With certain settings he can outacc
  • There would be legal and safety issues with modifying your car by ripping out the dash. And while you probably have a workable design in mind, your mention of "popup warnings" brings back scary reminders of Bonzi Buddy.

    Instead, "extend" your dashboard display by using a pocket PC or Sharp Zaurus to the side, displaying you what you want. This should be completely legal - people who use GPS maps do the same thing.

    Perhaps... perhaps the PDA could even be mounted above a non-essential display guage - say, t
    • What isn't legal about replacing parts in your own vehicle?

  • Speedometer precision not critical. (Score:4, Interesting)

    by sbaker ( 47485 ) * on Saturday February 05, 2005 @01:40PM (#11583505) Homepage
    Most manufacturers deliberately have their speedometers read high by several miles per hour (my MINI Cooper reads about 3mph high at low speeds - going up to 5mph high at 80 to 100mph).

    They do this for liability reasons. If for some reason the gauge is off by a little bit and you get a speeding ticket (or worse, you get into a wreck) - then they don't want you to sue them claiming that the speedometer was reading too low. By making them read a little high - then even if they get mis-calibrated (eg due to tyre wear, higher-then-recommended tyre pressures, etc) they still won't be reading *LOW*.

    So - if your LCD speedometer is off by a bit, you won't really be that much
    worse off than with the stock speedo.

    As someone previously suggested, you might want to look at the OBD-II specification. All cars sold in the USA in the last 10 or so years have a port located down under the steering wheel somewhere which delivers a wealth of interesting information in a more or less standard format. You can certainly read RPM for your tachometer - along with the rotational speed of each wheel independently and a bunch of other fun stuff. You could probably interpret the error code readouts it gives you to light up warning lights in a meaningful way.

    • I think it depends on your needs. I know the protocol for my car (ISO) is way to slow (for my tastes) for a real time tach and speedo. I think VPW is much faster but with ISO I get 3 or 4 samples a second. RPMs can change alot in 1/3 of a second.

      I don't think wheelspeed sensors are a standard OBDII sensor output. My car doesn't have mine available under OBDII. You can read them with the dealer tool though.
    • my MINI Cooper reads about 3mph high at low speeds - going up to 5mph high at 80 to 100mph

      How did you clock that? Whenever I've gone by one of those "please slow down" roadside radar speed indicator thingies, it's always been pretty much spot on. Around here they're usually on roads with 45 or 55 mph limits.
      • Those roadside gadgets also read high - for the same reason that speedometers do.

        I used a GPS to measure speed. It reads exactly right. But BMW don't make a secret over their deliberate high-reading speedometers.

        • Civilian GPS is only guaranteed within a few percent - which at 50MPH is 1-2 MPH (or more). Stick your car on a chassis dyno or have a friendly cop with radar verify your speedo. The chassis dyno time could be amusing anyway.

          Speaking of using GPS to monitor speed, though, have you seen the new Stewart-Warner speedometers that do just that? Pretty cool (until wartime comes and the GPS system for civvies goes to "pretty close, but not really accurate" mode)... I'm running an Autometer electronic speedo t
    • OBD wouldn't make a great choice for this; the update speed is much to slow for a really meaningful speedo or tach. You'd be better off reading the coil drive and Vss sensor directly.

  • I'm doing this too (Score:3, Informative)

    by dozer ( 30790 ) on Saturday February 05, 2005 @01:57PM (#11583635)
    I've chosen to install analog speedo, tach, H2O temp and oil pressure. This allows the LCD screen to be less expensive and less important so I don't mind as much when it's unreadable (say, a cold start at 0 degrees).

    Even with a good (transflective or super-bright backlit) screen, you'll need to ensure that it is shaded well against light from an oblique angle. Depending on your dashboard, that might be easy or it might be hideous.

    Right now I'm thinking I'll gut an IPAQ H3950 [ebay.com] running Linux to supply the display and controller. Apparently it has a good screen, and I'm sure it's rugged enough for automotive use. The battery will help a lot too. The one drawback that I can see is the screen is only 320x240. I yearn for 640x480, but I've been unable to find aything daylight readable in that resolution for less than a few thousand dollars.

    How to interface to it? Wifi! :)

  • Ken Thompson has an automobile which he helped design. Unlike most automobiles, it has neither speedometer, nor gas gauge, nor any of the other numerous idiot lights which plague the modern driver. Rather, if the driver makes a mistake, a giant "?" lights up in the center of the dashboard. "The experienced driver," says Thompson, "will usually know what's wrong."

    --Anonymous (from The Unix-Haters Handbook)

    • Sounds like the Microsoft car. "This car has preformed an illegal operation and will be shut down".. and if a reboot doesn't fix it, you have to reinstall the engine.

  • www.mp3car.com (Score:2, Informative)

    by hillg3 ( 656728 )
    Be sure to check out mp3car.com [mp3car.com]. I'm currently installing a PC in my car that will have an OBD-II interface. The forums there will probably be able to help you with your hardware and software selections.

  • Some details of my digital dash (Score:4, Informative)

    by shotgunefx ( 239460 ) on Saturday February 05, 2005 @04:22PM (#11584749) Journal
    I'm doing this myself now. I'm still in the early stages but have most of the parts. Just need to pick the computer itself and the power supply. (Probably go Opus with a ITPS)

    It's definitely going to be linux. I think I'm going to just put a half tower in the trunk as I'm going to need a lot of expansion cards.

    I'm leaving the gauges in place and putting the monitor (lilliput 8" touchscreen) in front of it and wrapping it up in custom fiberglass cowel.

    My wiring passes through the gauges into other systems, for instance the battery charger so it's easier to leave everything in place and easier to just remove screen and replace with stock cowel for inspection time. ;)

    For the harddrive, I'm using a ruggidized harddrive designed for automotive use. Slow but it's got a great temperature range and shock rating.

    The keyboard I'm using is a tiny one I found on ebay. I cut it down to fit in a 1 DIN position. It fits between the stock radio and AC controls. You don't know it's there when retracted.

    Most of the inputs will come from OBD-II (elmscan that I embedded inside floor) but it's not fast enough for the tach and speedo. (4 samples a sec at beast ISO) I'm tapping the tach, speedo and a few other input signals directly and processing them with a PIC. The PIC will then communicate with the PC via serial.

    I'm thinking later, I'll add a large commodity drive for other non essentials that will be activated via a temperature controlled relay. So if it's under 40F in the trunk, it won't power the harddrive until it is hot enough or maybe I'll just use a USB drive.

    My first advice is to buy the factory service manuals on ebay. They are invaluable. I got mine for $40 US. Three phone book size volumes with schematics as well.

    You might find the factory training books for the electrical and whatnot as well. I did. It was nice to have the whole ECU protocol detalied. (Though not planning to tap into it at this point)

    If possible, buy extras of whatever your going to mod on ebay. For most parts I'm fooling with, I have 2 or 3 extras that I've amassed over time. If your patient, you can get stuff cheap.
    For instance, in my spare room, I have a spare dashboard, gauges and most everything else on the dash. I'm using this to work on the fabrication so I don't have any downtime (or screw up my car)

    $1700 dollars worth of stuff righ there. $240 shipped in mint condition. Patience is the key.

    As far as the legality, I'm not concerned. If I had a massive failure, the only thing that I would be missing are my current speed, engine rpm, fuel and oil temperature. Nothing that would ever cause a crash. I can estimate the first 3 fairly accurately. Certainly enough to safely pull over and remove the screen and use the OEM gauges. A fuse could do the same thing to the OEM gauges (and has to me before)

    Besides the fact that I'll have more readings on my car (which will actually improve safety), In phase 2, I'm going (try) to tap the ABS wheel speed sensors. By using the four sensors, I've now added differential tire pressure monitoring to my car.

    My whole design goal is to have something integrated, yet I want it stealth. If you walked by, you'd have no idea it was anything special. You might if you were astute, notice the monitor, but you would probably just mistake it for a regular an OEM readout.

    A great site (Australian cars though) for technical car info and ideas is Autospeed.com [autospeed.com].

    There is some other stuff, but I'm not going into detail until it's done :)
  • Shouldn't be shaky -- if you get one of the breakout boards you can just solder the LCD wires right to the correct lines, then use the pxa framebuffer driver which is in the kernel. A number of people have done this, and seem to have had success with everything from eInk screens to boring-old color TFT screens. All the configuration that's needed on the software side is to plug a couple parameters into the kernel boot args.

  • Consider the following: (Score:3, Insightful)

    by Myself ( 57572 ) on Saturday February 05, 2005 @10:05PM (#11586906) Journal
    Response time has already been pointed out, but I think contrast ratio is much more important. LCD technology is not suitable for this application. Consider how bright the glowing needle of a modern gauge is, compared to the dead black of the face behind it. Or vice-versa, for the white-face gauges with thick black needles. An LCD has a continuous backlight and relies on each pixel to block light in its region. A little bit inevitably leaks through, resulting in the mottled gray that LCD makers euphemistically call "black".

    If the contrast ratio weren't bad enough, you have significant temperature and response time issues. Most affordable screens will go nearly blank in extreme hot or cold, as the controller's adjustment ratio hits its limits. Wide-thermal-range LCDs are expensive and have their own tradeoffs. At least you don't have to worry about viewing angle.

    Plasma displays would be better suited for this. By actually generating the light at each pixel, they solve the contrast problem pretty neatly. Their mechanism is also fairly temperature hardy. Interfacing color plasma displays is even more arcane than LCD though, so I wish you luck. If large OLED displays were available, I'd suggest them.

    Did you say skinnable interface [google.com]? Watch out for cock-shaped soundwaves. Holy shit, as if the usability of modern vehicles wasn't already bad enough.

    Anyway, a replacement for the stock cluster sounds a bit ambitious. Try an add-on panel for now. Actually using a PDA like you suggested sounds like a good way to start. Get your software worked out, for pulling the values off the bus and drawing gauges with low latency.

    One more thing just occurred to me: Have you ever watched the display of an LED clock jump around while chewing, or walking, or anything that makes your eyes wiggle a bit? Each segment is only lit for a small fraction of each second. LCDs don't suffer as much from this problem because the crystals in each pixel are slow to respond, but you still might get shimmer or wiggle as you go over bumps in the road. The refresh cycle of your display's controller will determine how obvious this is.

    Next issue: Getting the data from the ECM. OBD-II doesn't allow high refresh rates, last I checked. It's fine for watching parameters like throttle position and temperature, but a tach might not be practical unless you're reading straight off the CANbus. Alternately, try to get the data that the computer's already sending to the gauge cluster, in whatever custom format that is. The problem here is that this high-refresh-rate data is only sending the parameters that your existing gauge cluster needs to know about.

    I don't want to sound like a killjoy, but from the questions you're asking, this project sounds a little complicated. There's no harm in trying, but don't be disappointed if you end up with a marginally useful system. Publish your findings so that others can benefit.

  • dashwerks.com (Score:4, Interesting)

    by bergeron76 ( 176351 ) * on Saturday February 05, 2005 @11:39PM (#11587467) Homepage
    We can provide you with hardware in exchange for writing the software.

    We've been in this space for quite some time now and we're very familiar with it.

    Our site: www.dashwerks.com [dashwerks.com]

    We're linux and RTOS embedded...

  • Awesome! As people have pointed out - I think built in GPS would be a great feature if it were integrated.

    I think a reverse camera linked up the LCD would be great for parking as well...

  • "Stability is crucial, so I'm leaning toward a Linux-based system"
    You should be looking at embedded operating systems, such as VxWorks [windriver.com] which is what some of the real car manufacturers actually use [windriver.com]
    I would consider the display of a car a fairly mission critical application, and you want a system that's designed for these kinds of tasks. This isn't something you can bodge up and whack on a small PC [soekris.com] with an operating environment that hasn't been designed to do such things.
    Linux is far too complex for somet
    • I'd certianly agree with you about disabling safety features, but I think most drivers have a good feel for estimating their speed and engine rev. So I can't see a failure being a major safety issue in this context.

      The main reason is I'm using linux is prior experience and the availability of the tools I want. Obviously, that could change once I get further along if I find it's not in practice workable.
  • Why not to buy some complete spare parts lcd gauge panel assembly for some existing korean/japanese car, and mod it?

  • But I wanted to use a couple of IR cameras; one to display what's directly behind me and one pointed to the right front of the car to look for hidden cop cars. A bright IR illuminator should make that reflective paint on cop cars stand out quite nicely.

    LK
  • Just a FYI; but LCDs will wash out very badly in sunlight, and you want to be able to read your gauges in the daytime. Try using a PDA on a bright day in the car and you'll see the problem.

    This is the primary reason that the old-style gauges are still the standard. You can even get "digital" analog gauges driven by servomotors.
    • Yeah, I thought about that. Xenarc has an ordering option for extra bright screens.

      For my project, I have a coupe and the amount of light coming in from the rear is not bad at all.

      So I'm going to compensate for it with the custom cowel. Due to the configuration of my interior, (my gauges are pretty far away. About 1ft behind the steering wheel, deeply recessed.) I can bring the sides around the lcd forward a good 6 or 7 inches. The back window is tinted really dark so the light that could potentially hi
  • Remember that automotive manufacturers go to a great length in research and engineering, to design user interfaces that are easy to read and provide useful information quickly and efficiently. That said, looking at a variety of cool user interfaces might provide you with interesting ways of communicating Status [GOOD] . Status [Warning] . Status [Danger] ...

    You could come up with an ALCARs type interface, of as you mentioned skins...

    One of the big problems with automotive environments is that they are
  • out of one of these [thinkgeek.com]?

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