Saturday, 7 February 2015

Focaltech touchscreen oops / Leagoo customer service


I've been playing around with the Leagoo Lead 3 for some time now. Initially I chose this due to price and the fact that it was not just another "counterfeit samsung" like many others. Apart from it having a fairly low spec (but still great for £50!) I really like this in terms of build quality, official ROM update availablility, and as I've just found out, Leagoo customer service is great too!

Nice packaging

It's an unbrickable device - even a full eMMC wipe can be recovered from as the SoC has an internal bootrom that will emulate a low speed uart over usb, which you can then flash the preloader back and go from there.

There is however one more "secret" flash storage area that unfortunately can be erased. It turns out that Focaltech CTPMs have an 8051-based controller with... firmware stored in its own flash memory. A couple of days ago I (somehow) managed to wipe the contents of one, rendering the touchscreen completely useless. The device that you need the part number from is this:


I tried a bunch of random firmwares with (obviously) no luck. They're each tailored to a specific screen. In a last ditch attempt before microwaving the brick* I contacted Leagoo customer services to see if they would send me the firmware. A few emails later... I got it :)

Working touchscreen again

The strange device-to-host i2c comms of this thing still confuse me, but it should be possible to write a kernel module to dump a backup of the firmware which could come in handy when dealing with phones from companies with useless (or nonexistent) customer service *cough* Cubot, Axgio, Landvo *cough*



*and of course a closer look at the mainboard - if anyone has a broken Lead 3 they want to send me for that purpose then I will do!

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