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Thread: tablet to replace speedometer. auto turn on/off?

  1. #1
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    tablet to replace speedometer. auto turn on/off?

    hello forum.
    in my car, i have a diagnostic module, wich is basically an arduino, that reads all my sensors, does the neccecery calculations, and sends a string to my pc.
    so far i had use my computer as speedometer. but since it takes forever to turn on, i find its better to use a tablet instead, in the place where my old speedometer used to be.
    the tablet will be 9" (cause the only screen diamteres that fit my speedometers place are 7",9",and 12,3 " ), and i hope to receive the string from the arduino, via bluetooth comunication.

    My main concern, is how would i make the tablet, turn on and off (i mean the sleep, wake that ARM proccecors do), when the ignition is turned on and off.
    the only way i have though so far, was to hardwire the tablets button, to enother circuit that send pulses when ign is on or off, but this seems pretty risky, adn i would like a more non invesive way... something that would have to do with the tablet being charged or not maybe??

    anyone have any ideas??or, has done something like that before??
    thanks allot!

  2. #2
    Constant Bitrate eugenweij's Avatar
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    takser is an app you can use , it can be set up so your tablet wakes as soon as charging of battery begins, and to go to sleep as soon as power is cut off.
    the only thing you would have to do it get a car charger that turns on when ignition is on.
    View my worklog here

  3. #3
    Variable Bitrate
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    so simple? and i was about to hack open a brand new tablet to do it thanks allot mate! you saved me allot of time!!
    as for the charger, since the tablets charge with dc (5,9 or whatever), i was thinking to just use a DC-DC converter, that gets power directly from the ACC line!!

  4. #4
    Constant Bitrate eugenweij's Avatar
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    that can be done, or you can find a car charger for your tablet and hack that to connect it to the acc line
    View my worklog here

  5. #5
    Variable Bitrate
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    cool. thanks again mate!!

  6. #6
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    It was done before, I've seen it on another forum (Don't remember which).

    Make sure your car is on the newer CAN protocol, if your car is on the older KWP or ISO protocols the rate of updating the values will be too slow to use.

  7. #7
    Variable Bitrate
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    As I sed. The diagnostic is made by me with an arduino .. I have arledy made it work on my of. I just want to upgrade to ARM

  8. #8
    Variable Bitrate
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    well, something else. if the tablet , has just one USB port (no other DC-jack) , and it gets charged from the usb port, You cant have enything else connected, when the tablet charges??

  9. #9
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    You can if the kernel supports it. AFAIK only the Nexus 7 with Timur's rom can do that.
    settra likes this.

  10. #10
    Variable Bitrate
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    something else: i some times , have many days to use the car (5, can be very easy 7-8).. in that time, even the tablet , in sleep mode, will completely discharge.... and even after that many days, if i drive, i will drive for no more than 30minutes ... so it wont charge back up. so i was thinking, to build an "inteligent " charging system:

    meaning, i would use an arduino, to activate the tablets charger, every 3-4 days, and keep it active for like 4 hours..
    i replace the auto on/off on charge , with USB connection (since, it will have usb connection only when the car is turned on).
    the problem is, that for some stupid reason, most of the ARM'S , by DEFAULT (no tasker or anything like that), turn ON when you apply charhing... meaning that the tablet will turn on, every time the arduino decides to charge it....

    any idea how to bypass that??

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