AM335x with LCD and Flash?

Hi Ben,

The aforementioned link (taken from another post) is incorrect. Please use the pinmux tool located here: http://processors.wiki.ti.com/index.php/Pin_Mux_Utility_for_ARM_MPU_Processors 

Thanks Michael, that link works.

But it confirms that LCD and the GPMC conflict. Shame, the processor looked good for us otherwise.

Hi Ben,

Keep in mind that not all 24-bits of data line are needed for every LCD mode (the pinmux tool shows all the pins when you check a module, but it's not always required). If you use 16-bit pixel data, the pins mapped to [16:23] can be used for GPMC. You can also experiment with various GPMC modes that use less pins. Please refer to the TRM http://www.ti.com/litv/pdf/spruh73b for modes for both - it is possible to run both at the same time (note that our EVM does this, the schematic for this may also help).

Thanks for those pointers Michael, I'll look at those trade offs more closely. And check out the use on the eval board.

Have a good Christmas.

Can you please explain the Am335x EVM LCD connections?

In the LCD board schematics, LCD0-LCD15 pins from the CPU are connected like 16bpp connection and LCD16-LCD23 pins from the CPU are connected to the LSbits of the LCD RGB color input lines. Also the LCD16-LCD23 pins of the CPU are distributed among RGB inputs to the LCD.

1) Is this setup 16bpp or 24bpp?

2) What is the trick used to connect the LCD16-LCD23 bits of CPU to the LSbits of the LCD color channels?

3) Can we directly connect the LCD0-LCD23 pins from CPU to the LCD RGB inputs one-on-one?

I spent nearly two weeks to understand the AM335x LCD interface and AM335x LCD schematics. But still I am not clear. Will appreciate any help in explaining the Am335x EVM LCD interface.

The link: http://www.ti.com/litv/pdf/spruh73b does not work.

Thanks & regards

R.Sada

Jayel Systems

Sada

Please look at the device errata which explains the LCD connections and limitations. Here's the relevant extract...

  Paul

Hi Paul,

I am developing a board with the AM335x and a 7" LCD panel. I would like to know if there is a way to configure the LCD controller to use an 18bit interface. As I have read, the 2 modes are 16bit  and 24bit. I do not want to use the 24bit mode since I need to re-configure LCD-D18 to LCD-D23 to alternate functions.

Can I set the LCD controller to 24bit mode and then use only LCD-D16 & LCD-D17 pins (along with LCD-D0 to LCD-D15) to get my 18bit LCD bus ? In this configuration, can I re-program the LCD-D18 to LCD-D23 lines for an alternate function since I am not using it for the LCD interface ?

Regards,

Raj

http://www.ti.com/lit/er/sprz360/sprz360.pdf

Raj Kumar said:

Can I set the LCD controller to 24bit mode and then use only LCD-D16 & LCD-D17 pins (along with LCD-D0 to LCD-D15) to get my 18bit LCD bus ? In this configuration, can I re-program the LCD-D18 to LCD-D23 lines for an alternate function since I am not using it for the LCD interface ?

Raj

Sorry, I missed your post.

Yes, you can set the LCD controller to 24-bit mode and use only LCD_DATA[17:0] to drive the display and use the other bits for the alternate function by setting the pinmux appropriately. Will you bee connecting to a 18-bit or 24-bit display?

  Paul

Hi Paul,

I plan to use a 24bit LCD panel operating in the 18bit mode. I need to use the LCD Data20 ~ LCD Data23 lines to connect to MMC1 DAT0 MUX0 ~ MMC1 DAT3 MUX0.

So the sequence of initialization would be :

1> Configure LCD to 24bit mode (Mode 1), the LCD is physically wired on LCD Data0 ~ LCD Data 17 (18bit)

2> Configure MMC1 DAT0 ~3 MUX0 (Mode 2)

Right ?

Any other issues I need to watch out for  in this configuration ? In my design, the LCD Bus and the MMC1 interface will run at 3.3V.

Regards,

Raj

Raj

Looks good.

Since you are using a 24-bit display you'll need to either tie-low the unused panel inputs or connect them to other active bits.

Make sure you understand the connections RGB888 as detailed in the errata.

  Paul

Hi Paul,

The LCD panel has a pin to select 24bit or 18bit mode. In the 18bit mode it performs dithering to get the 2 extra bits per colour. I have noted the LCD bus pinouts in the errata sheet.

Regards,

Raj

Raj Kumar said:

Hi Paul,

The LCD panel has a pin to select 24bit or 18bit mode. In the 18bit mode it performs dithering to get the 2 extra bits per colour. I have noted the LCD bus pinouts in the errata sheet.

Regards,

Raj

Great!

  Paul

The nand in evm uses 8bit (A/D) mode. not 16bit (A/D)

Hi, Paul

I noticed that hardware leakage between TFT 16bits mode and 24 bits mode are annonced as "Revision 1.0 Usage Notes and Known Design Exceptions to Functional
Specifications", per errata sprz360.pdf.

Does that mean this design exception will keep consistance in am335x future silicon revisions, like say 1.1 or 1.2 or 2.0?

Thanks

Weidong

PaulM said:

Sada

Please look at the device errata which explains the LCD connections and limitations. Here's the relevant extract...

  Paul

 

At this time, TI does not plan to change the LCD color assigments to LCD data terminals in future versions of AM335x.

Regards,
Paul

Hi Paul, I was following that conversation but have a further question:

comparing the EVM schematics and the silicon errata it seems that on the EVM connections between AM335X and LCD follow the scheme defined for RGB565 mode. LCD_Data_15 is R7.

But the LCD on EVM is connected via 24 data pins with LCD_Data_23 being R0

The connection between AM335X and HDMI transmitter on EVM seems to follow the scheme defined for RGB888 mode.

Now, we don´t understand how the EVM can work in RGB888 mode. There is a crossover option on the board but it is not stuffed on the one we bought.

As our HW should support both options please let me know if the EVM only supports RGB565 and the crossover resistor arrays would need to be changed to support RGB888 or if we are somehow wrong.

Thanks,

Christoph