Screen ok but touch swaped l/r?

Discussion in 'Chit Chat' started by KMatle, May 20, 2015.

  1. KMatle

    KMatle Expert Licensed User

    I've bought a car Android DVD system.

    Starting the motor

    a) it boots when it was turned on before


    b) you have to press the on knob, then it boots

    ONLY in case a) the touch events behave like the screen has been rotated arround the y axes, so if you touch it most left will cause a touch event most right. Touching it most right will cause a touch most left. Like a mirror. Vertical touches are ok and - except of the l/r mirroring - the touch coordinates are ok.

    Seems to be a problem due to high power comsumption while starting the motor.

    Any ideas how this works? How does Android "mirror" the touch events? (The screen displayed correct).
  2. Troberg

    Troberg Well-Known Member Licensed User

    I would guess that it's something wrong with the screen orientation. Have you tried turning the car upside down, then back again, to force an update (this is a very Microsoft inspired suggestion, I know)?

    Or, possibly, set screen orientation in code, so that you lock it down to the correct orientation.
  3. Cableguy

    Cableguy Expert Licensed User

    Have you tried stepping out of the car and back in again (again M$ inspired). But now seriously... Try to put a current limiter and a voltage regulator just before the radio... Most car radio shops have these in a single easy to connect box. The current surge to the motor makes the voltage go down for a few secs... Maybe that's the problem.
    KMatle likes this.
  4. KMatle

    KMatle Expert Licensed User

    I've completely removed the motor after turning the car upside down. The radio boots correct now. Yessss!!!! :D:D:D
    But now the battery does not charge. Any ideas? Microsoft refused to help me here because some of the drivers (I thought I was the only one) are not are not digitally signed. Hm.


    Yep. I think it's a voltage-down problem, too. When I switch it off before shutting down the motor (so it won't boot directly), it's ok...
  5. Troberg

    Troberg Well-Known Member Licensed User

    A good idea is to put a large (the larger the better) capacitor on the incoming power. Just put it between + and - (make sure you get the polarity right, large capacitors usually require that).

    It will have several good effects:

    * The capacitor acts like a reservoir, which can store a little power, enough to smooth out small dips.
    * The capacitor acts like a filter. When starting and stopping the engine, you can get power spikes. These can potentially damage electronics. However, these are very short, in other words, high frequence. High frequence signals pass straight through a capacitor, so they are harmlessly led back to the battery, without reaching the device.
    * As it filters the power, it also reduces hum that might occur from interference from other systems.

    A very cheap insurance against problems. Costs next to nothing, and, if you are cheap, you can probably salvage one from an old computer power supply.
  6. Cableguy

    Cableguy Expert Licensed User

    By large he means about 4700microfarads/50v electrolyte cap, usually round things! LoL
  7. ac9ts

    ac9ts Active Member Licensed User

    I might add: Add a diode between the battery+ and the cap. You'll need a relatively large diode depending on the current draw of the Android DVD system. Get a diode rated at least as 2X large as the fuse.

    The diode voltage drop from the battery shouldn't affect the use of the DVD and, with the cap on the DVD side, will help isolate/stabilize the voltage. With the large current draw (and voltage drop) of the starter motor, just adding a cap won't do much good as the voltage on the cap will drop with the battery voltage.
  8. Toley

    Toley Active Member Licensed User

    Hi KMatle, I don't have any problem with mine which seems to be a similar model. So I would also guess on a power issue.
  9. Cableguy

    Cableguy Expert Licensed User

    Get a DC/DC converter... Input 7~18 output 13.8(this is the typical car batery output) and add that final cap in parallel to it DVD side
  10. Cableguy

    Cableguy Expert Licensed User

    You could also get a delay circuit, which would only provide vcc to the DVD a few secs after power on... This as an optional extra...
  11. RandomCoder

    RandomCoder Well-Known Member Licensed User

    It maybe stating the obvious but how old is the car battery? My wife's battery on her Ford C-Max would start the car fine normally but on very cold mornings it tended to struggle a little and occasionally the indicator lamps would flash whilst starting. New battery fitted and it now starts up incredibly easy all weather's and no more lights flashing when they shouldn't. You can normally get a battery check free of charge at most car part shops.
    Cableguy likes this.
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