Capacitive Touch with A20

[dave-at-axon]

My first stage of adding a capacitive touch 7" LCD to the A20 is working. I still have to add the touch drivers but the LCD manufacturer supplies a Linux driver which I have compiled into the Android Linux kernel. I need to add an interrupt for it. There was no changes to the LCD timing and this works with the Olimex 7 settings even though there is no HSYNC or VSYNC for this display.

The display is much brighter than the Olimex 7" due to the higher brightness LED backlight and the fact that capacitive touch does not reduce the light transfer as much as resistive.

All the code for this will appear on my blog once it's all working. I may around the same time offer the PCB interface for this but at this time I don't have a costing for this yet.

Here's an image of the LCD in action. I am using the Fusion F07A-0102 LCD and it comes with the touch panel already bonded to the LCD. I have a custom made PCB that fits to the rear of the LCD panel and this has the standard 40 way header that matches with the Olimex LCD connector. There is an additional UEXT connector for the touch as the Olimex 40 way does not have the required I2C interface for the touch.

[martinayotte]

Congratulations, Dave !

I'm happy that some capacitive LCDs will now works with Olimex boards.

I presume, if I need to go to capacitive way in a future, that your work should be compatible with the bigger Fusion F10A-0102 from the same company, Touch Revolution ?

[dave-at-axon]

It should work but I need to check the larger LCD's LED backlight to make sure that it can driver it.

The rest is down to timing settings in the software for the LCD itself and configuration for the touch driver in the fex file.

It looks like the touch driver will work out of the box after some configuration changes. Allwinner provide an interface to cap touch and it looks like just a configuration issue. Fingers crossed but still waiting for the 6 pin connector for the touch interface. Damn thing was on 6 weeks delivery! Next week I should know.

[dave-at-axon]

I just checked the datasheet. The 10" panel is actually LVDS so will require a different driver and PCB for it. No big issue as the A20 can be configured for LVDS as some have already done with it.