BBB Framebuffer : Need Ideas.

Christian Mauderer christian.mauderer at
Wed Jul 10 07:10:25 UTC 2019

On 09/07/2019 21:13, Vijay Kumar Banerjee wrote:
> Hello all, 
> First the status :
> * The fbd has been ported and it's attaching with the fb0 devie. There's
>    an fb0 device entry created. 
> * In the following commit I have added mmap to libbsd. This works like a
> wrapper to the mmap in cpukit
> Blocker : 
> * After the fb0 is created and mmap is added, I don't see anything on
>   the screen. From the FreeBSD, it seemed like the VT driver is needed
> and that is responsible for turning on the screen. So I have ported a
> minimal version of the VT with only the initialization and allocate parts:
> But even after porting the VT driver which initializes well ( As the
> message during booting says). I don't see anything on the screen.
> I need some ideas on what is missing or how to debug this. 
> The app I'm using to test framebuffer is pushed here :
> Any idea regarding this is greatly appreciated.
> Thanks,
> Vijay

Hello Vijay,

did you have a look at the SPI of the HDMI framer? What is it used for
according to the data sheet? Is it necessary for the driver?

>From our chat discussions and my own tests I know that the screen is
still not receiving a signal. So I would assume some quite basic
problem. If your new mmap wouldn't work, you should still get at least a
black screen.

Best regards

embedded brains GmbH
Herr Christian Mauderer
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