Taming the Lapdock 100 (for a Raspberry Pi)

You can pick up a Lapdock 100 for around £50 – which for a mouse, keyboard, screen and battery combination is hard to beat.  Naturally as its not a solution specifically for the Pi its not just plug and play.  The Lapdock connectors consist of a HDMI micro plug and micro USB plug, so you’ll need to buy some adaptors and for best results be prepared to do some soldering.  There are guides for building a Y cable all over the place many of varying quality from mediocre to poor (I did loose one that was really good – if I find it I’ll edit it in here!)

Apparently with later models of the Pi its a moot point but I found that any USB plugged into the (non power) USB sockets of the Pi would light the power led but not boot the Pi.  Basically your Y cable should pass data +/- and GND to a usb DATA port and just GND and +5v to the Pi’s usb micro socket.

I found a great deal of conflicting information about the Lapdock 100 some people seemingly with the belief it simply could not be used with the Pi.

While there are some caveats I have found it to work just fine.

Make sure the config.txt is set correctly to make the HDMI active all the time.

You are better powering down without the mains lead in and in fact to get the Lapdock into a state where it will boot your Pi with the screen active (or at all) you must disconnect the Pi’s power connector and also the Lapdocks power.

Assuming both are disconnected or you were just running from battery (with the Pi’s power disconnected),  you need to wait for the LED in on the Lapdocks “power button” to flash.   If you’ve forgotten to unplug the power lead before shutting down (do it now) it could take 30 seconds or more after everything is disconnected.  Running with just the battery when unplugging the Pi’s power it usually only takes 5 or 6 seconds to flash the LED (but sometimes longer)

Now the Lapdock is in the “post LED flash” condition one of two things will make the Lapdock power up the Pi and its display, either press the Lapdocks power button or plug in the Lapdocks power lead.

I’ll be adding a switch to the power side of the Y cable and be looking for a shorter HDMI cable – then with the addition of some velcro I should have quite a nice Pi Laptop.

As for the Lapdock itself the screen is really nice very clear and steady, the mouse is okay with the exception of the right mouse button (but I might have just got unlucky) – the keyboard itself is not the worlds best, especially the space bar which is quite poor sometimes registering two hits and sometimes none.  Generally the feedback from the keys is not great, but it works!

So if its a dodgy low res LCD from Hong Kong or the Lapdock, I’d have to say the Lapdock has it.

2 thoughts on “Taming the Lapdock 100 (for a Raspberry Pi)”

  1. We have 2 Lapdock 100’s to try with Raspberry Pis .. and its a very different situation to the Atrix model! We have had ‘success’ with both a Model B V2 and a B+…
    We have found that the ‘critical’ aspect is the timing of connecting the HDMI connector between the units ‘to catch the HDMI dialogue’ at the ‘right time’??? it seems.

    As with the Atrix Version, it also has to be remembered that; if connected, the Lapdock will try to power the Pi, at all times, and that this is interrupted, for some reason, during part of the lid-opening.

    With Raspiam Linux running, we have started the Pi, and then ‘opened the lid’ of the Lapdock 100 … after about 5 seconds the screen will come on … THIS IS THE TIME to connect the HDMI connector – and the screen then remains on for as long as required (assuming the lid is not partly closed to look at the rear connectors 😎 )
    The external power can be connected, if not previously.
    AN IMPORTANT NOTE – for no ‘known reason’: once the 100 has ‘powered up its screen and then shut it down (presumably to save battery power to charge the Motorola phone) … you must wait several minutes, with the Lid CLOSED and HDMI disconnected before trying the sequence again.
    We have done this with both external power adapter, and Pre-charged Lapdock100 to power the RPi (a switched USB to Micro power connector), AND with and without a Network connection (which affects start up time particularly in some RISCOS images)
    WE HAVE NOT YET HAD RELIABLE SUCCESS when starting up in RISCOS … and we susupect it is some of the Screen Modes (640×480 for example) appearing during the start up sequence that is having a detrimental effect on the HDMI dialogue:
    This dialogue, and how to intercept it needs some more investigation. in the meantime we will use the Atrix for RISCOS and the 100 for Raspian Linux.
    I have short HDMI-HDMI mocros leads on order to avoid the stresses of heavy adapters on fragile-mounting micro connectors!!

    1. Sounds like you’re making hard work of it! try this
      next time you shutdown…

      1 unplug AC adaptor before shutting down
      2 when Pi shuts down (10 rapid flashes on OK LED) unplug Pi’s power conector (micro usb connector)
      3 wait for LED on Lapdock 100 to flash briefly (this could take 30+ seconds sometimes)
      4 you can plug the Pi’s power back in now its not powered (leave the hdmi cable alone!)

      If closed down in this manner you will not experience the joys of 5-20 seconds of power then a reset.

      to start
      1 with lid OPEN, leave AC adaptor disconnected, leave HDMI cable can be plugged in all the time
      2 either press dock’s “battery check button” or plug in AC adaptor

      NB if you want to charge the battery leave the Pi disconnected and the AC adaptor plugged in BUT before you next boot you MUST disconnect the AC adaptor and WAIT for the LED flash on the docks power button.

      The is 100% reliable, providing you have shutdown properly following the above, also note it is important that usb part of the lapdocks cable is drawing power (and possibly needs to be connected to a usb host too, but not verified), use it to power Pi as well as provide keyboard/mouse with a Y cable…

      I have not verified with many HDMI cables but some cables do NOT properly ground the detection signal, if these instructions don’t work for you DO try another cable (and another…. etc)

      With a simple switch to interrupt the Pi’s power you should be able to leave all the cables in place.

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