Direct LCD Drive

Tabulous
Posts: 445
Joined: Fri May 03, 2013 12:02 pm
Has thanked: 1 time
Been thanked: 12 times

Direct LCD Drive

Postby Tabulous » Mon May 27, 2013 2:57 pm

Does this driver support TFT direct drive, i.e. directly driving TFT with out using a GDC ?

User avatar
Tectu
Posts: 1226
Joined: Thu May 10, 2012 9:50 am
Location: Switzerland
Contact:

Re: Direct LCD Drive

Postby Tectu » Mon May 27, 2013 3:09 pm

What do you mean by this driver? If you provide a driver to the GDISP module which is able to handle setPixel() calls, then you can use it without any problems.


~ Tectu

Tabulous
Posts: 445
Joined: Fri May 03, 2013 12:02 pm
Has thanked: 1 time
Been thanked: 12 times

Re: Direct LCD Drive

Postby Tabulous » Sat Jun 01, 2013 11:36 am

See this application note from ST, basically directly driviny a TFT without a controller chip.

http://www.st.com/st-web-ui/static/acti ... 278141.pdf

User avatar
Tectu
Posts: 1226
Joined: Thu May 10, 2012 9:50 am
Location: Switzerland
Contact:

Re: Direct LCD Drive

Postby Tectu » Sat Jun 01, 2013 2:41 pm

ChibiOS/GFX does not care about how you write to the display. If you can provide a driver which does handle this function call, it will work:

Code: Select all

void gdisp_lld_draw_pixel(coord_t x, coord_t y, color_t color);

What you'd have to do is simply manipulate the registers inside the STM32 to drive the direct LCD drive peripheral, instead of sending some SPI commands to an external controller like other drivers do.

TL;DR -> yes, it will work.


~ Tectu

mobyfab
Posts: 418
Joined: Sat Nov 19, 2011 6:47 pm
Location: Versailles, France
Has thanked: 2 times
Been thanked: 5 times

Re: Direct LCD Drive

Postby mobyfab » Sat Jun 01, 2013 5:52 pm

To drive a TFT panel directly, you have to generate 3 clocks: VSYNC, HSYNC and the pixel clock. Also you need a parrallel port to write the data.

You'd have to write a driver to work with STM32 as you will have to use the timers and DMA controller.
As long as you have an FSMC and some SRAM it's possible.

Also the new F4x9 devices have an integrated TFT driver and DDR controller, it would be much easier/cheaper to make it work and performance would be best.

To write data to the screen you just need to write to the frame buffer.

Tabulous
Posts: 445
Joined: Fri May 03, 2013 12:02 pm
Has thanked: 1 time
Been thanked: 12 times

Re: Direct LCD Drive

Postby Tabulous » Mon Jun 03, 2013 12:06 pm

mobyfab wrote:To drive a TFT panel directly, you have to generate 3 clocks: VSYNC, HSYNC and the pixel clock. Also you need a parrallel port to write the data.

You'd have to write a driver to work with STM32 as you will have to use the timers and DMA controller.
As long as you have an FSMC and some SRAM it's possible.

Also the new F4x9 devices have an integrated TFT driver and DDR controller, it would be much easier/cheaper to make it work and performance would be best.

To write data to the screen you just need to write to the frame buffer.


As per my post link to STM Appnote on Direct Driving :-)

PS F4x9 devices are not currently available, they are not released to mass market. Also this will not be the cheapest solution, i dont need 180Mhz with DSP.

Tabulous
Posts: 445
Joined: Fri May 03, 2013 12:02 pm
Has thanked: 1 time
Been thanked: 12 times

Re: Direct LCD Drive

Postby Tabulous » Mon Jun 03, 2013 12:10 pm

Tectu wrote:ChibiOS/GFX does not care about how you write to the display. If you can provide a driver which does handle this function call, it will work:

Code: Select all

void gdisp_lld_draw_pixel(coord_t x, coord_t y, color_t color);

What you'd have to do is simply manipulate the registers inside the STM32 to drive the direct LCD drive peripheral, instead of sending some SPI commands to an external controller like other drivers do.

TL;DR -> yes, it will work.


~ Tectu


Mmmmm as the direct drive implementation DMA's display buffer from SRAM to the Display, all that should be needed is to get

void gdisp_lld_draw_pixel(coord_t x, coord_t y, color_t color);

writing to the correct SRAM locations. Could be very simple this :-)

User avatar
Tectu
Posts: 1226
Joined: Thu May 10, 2012 9:50 am
Location: Switzerland
Contact:

Re: Direct LCD Drive

Postby Tectu » Mon Jun 03, 2013 12:13 pm

That's correct :)


~ Tectu


Return to “LCD Driver and Graphic Framework”

Who is online

Users browsing this forum: No registered users and 1 guest