0 Replies Latest reply on Jan 6, 2011 10:03 AM by Kelv

    Apad Tear down


      With the anticipated explosion of tablet devices in 2011 at CES I thought it’s about time I purchased one and find out what its all about.


      There are a number of difference processors used in these devices some high end others are basically 5 year old PDA technology with a bit of spit and polish to make them look modern.


      Of the more interesting devices available I was drawn to the I.mx515 based clone that is currently doing the rounds of a Chinese wholesaler on a website near you.



      800Mhz Cortex A8 cpu,

      512M DDR ram ,

      4GB internal SD (in place of NAND)

      8” TFT LCD, (HL08009 C25 XY, 800x600)

      G-sensor, (Freescale mma7660)

      Wi-Fi (Atheros AR61026)


      Noticeable features missing are Bluetooth and 3g. Blue tooth is supported as a USB device and as I found so are 3g dongles, but more on that later.


      This was exactly what I was looking for; relatively cheap at around £100 - £150, a capable processor and more importantly it was running Android 2.2, which means an improved web browsing experience with flash support.


      One thing to keep in mind with these “clone” devices is they are little more than a barebones dev kit, not 100% ready for prime time.  As such there are a few interesting “Features”…


      First thing to investigate , “Jittery” input from the resistive digitiser, as usual the internet is full of helpful people posting supposition and general guess work, but there are one or two people out there that have a more logical approach, with a solid grounding in electronics development who believe it is related to EMI/RFI from the power supply.


      After disassembling the pad and running the digitizer as far away from the body as possible it becomes apparent that it is related to interference. Unfortunately I damaged the digitizer trying to position it in such a way that I could get a probe into it whilst it was running, not to worry though as replacements were available for $19, I ordered 2 just in case my clumsiness comes to the fore once again.


      However after fitting the replacement touch screen my "jitters" appeared to calm down substantially, so much so that it no loger effects the usabilty for me.


      In the meantime I backed up the SD card using the Linux ‘dd’ command to take a raw dump of the internal SD card and have started tweaking away safe in the knowledge that I can restore it to stock in no time flat.


      More to follow