Hello.
Consider we have a VersatilePB board (QEMU emulated) with a screen.
The question is: how to put a pixel(or something more interesting) to the screen, using C or ARM assembly?
I`ve searched for a long time, but didn`t find anything useful
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| ARM framebuffer https://forum.osdev.org/viewtopic.php?f=1&t=23990 |
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| Author: | bazhenovc [ Sun Aug 14, 2011 12:24 pm ] |
| Post subject: | ARM framebuffer |
Hello. Consider we have a VersatilePB board (QEMU emulated) with a screen. The question is: how to put a pixel(or something more interesting) to the screen, using C or ARM assembly? I`ve searched for a long time, but didn`t find anything useful
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| Author: | jnc100 [ Sun Aug 14, 2011 1:55 pm ] |
| Post subject: | Re: ARM framebuffer |
I believe its an ARM PL-110: http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0161e/index.html although it has been changed to be modelled as a PL-111 in the latest qemu repository as of the end of July. Regards, John. |
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| Author: | diodesign [ Sun Aug 14, 2011 2:04 pm ] |
| Post subject: | Re: ARM framebuffer |
bazhenovc wrote: Hello. Consider we have a VersatilePB board (QEMU emulated) with a screen. The question is: how to put a pixel(or something more interesting) to the screen, using C or ARM assembly? I`ve searched for a long time, but didn`t find anything useful Read up on VersatilePB and ARM CLCDC PL110 documentation from ARM, it's all in there and just a google search away. The CLCD controller's registers start from 0x10120000. You need to program the following registers (one of which is a SoC clock control register)... SYS_OSCCLK4 at 0x1000001C CLCD_TIM0 at 0x10120000 CLCD_TIM1 at 0x10120004 CLCD_TIM2 at 0x10120008 CLCD frame buffer physical base address at 0x10120010 CLCD control bits at 0x10120018 This table has some useful numbers for you: http://infocenter.arm.com/help/index.js ... hedgd.html Let's say you want a SVGA (800x600) display. Look up the resolution you want in the table above and the magic numbers needed for the hardware, and check the manuals. This is the C code you'll end up with: *(volatile unsigned int *)(0x1000001C) = 0x2CAC; /* timing magic for SVGA 800x600 */ *(volatile unsigned int *)(0x10120000) = 0x1313A4C4; *(volatile unsigned int *)(0x10120004) = 0x0505F657; *(volatile unsigned int *)(0x10120008) = 0x071F1800; *(volatile unsigned int *)(0x10120010) = (1 * 1024 * 1024); /* base addr of frame buffer */ *(volatile unsigned int *)(0x10120018) = 0x82b; /* control bits */ From the LCD controller datasheet, you'll discover exactly how to control the hardware - I just lifted the above code from some really old crappy test I wrote to make sure the LCD controller was working on QEmu's VersatilePB support. It's horrible. After that, it's a case of writing pixel data to the frame buffer (I believe the default format is 0x00BBGGRR) CLCD controller information: http://infocenter.arm.com/help/index.js ... 13915.html VersatilePB programmer's guide: http://infocenter.arm.com/help/index.js ... haagj.html Hope this points you in the right direction. |
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| Author: | bazhenovc [ Sun Aug 14, 2011 2:36 pm ] |
| Post subject: | Re: ARM framebuffer |
jnc100, thank you, this is it. diodesign, thank you so much! You saved my day 
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