On Monday, September 30, 2013 2:15:22 PM UTC-4, [email protected] wrote:
>
> Yeah. I think I can disable the onboard HDMI framer and enable my own LCD
> display through the cape manager at runtime or set it in the Env.txt to do
> it at boot process( as I have read from here
> http://learn.adafruit.com/introduction-to-the-beaglebone-black-device-tree/exporting-and-unexporting-an-overlay
> ).
>
It would be easiest to disable the onboard HDMI framer at boot time, and
then you can test enabling and disabling the LCD display via the cape
manager.
IE modify the DTS. Don't even worry about touchscreen for now, just focus
on graphics.
Modify and compile the DTS, place the compiled mods into the /firmware
directory and then send the file name to the cape manager, ie
echo yourfilename >/sys/devices/bone_capemgr.*/slots
The file is fairly self explanatory and as long as your sticking with 16
data lines your in good shape.
>From the BB-BONE-LCD4-01 file you would delete the following sections:
tsadc - this is for the touchscreen, just remove it for now to avoid errors
while loading it
gpio-leds-cape-lcd4 - this is for some status led's on the lcd. While
they should not cause any problems, if you remove the section then you
won't have any problems
The panel section is the important one:
panel {
compatible = "tilcdc,panel";
...
This tells Linux that it should load the tilcdc panel driver and gives the
configuration information. Normally, the tilcdc driver would be loaded
upon bootup and when a new device was found[either from the hdmi connection
or from an i2c connection] it would auto configure based on the data.
Since your just using a raw LCD panel, you have to manually load it. Make
sure to adjust the panel-info and display-timings section to match your LCD
configuration.
One of the really cool things with the device tree is how you should be
able to configure/adjust settings for all sorts of drivers automatically.
Pre-device tree tended to require a seperately compiled "driver" for every
variation. Browsing through older video drivers, I find large numbers of C
files that only exist to define panel timings for different models of
LCD's. These files are duplicated in lots of different video display
drivers to add the panel definitions there.
Wheras with the device tree and TI's addition of support for fragments, you
can place the timing information in one DTS fragment, and then include
those fragments in the DTS file on a driver by driver basis.
--
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