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OMAP-L138: LCD LIDD Use both Enables for Character LCD

Part Number: OMAP-L138

Hi All

I We are trying to use both LCD Enables on LIDD LCD controller on OMAP-L138

We are using character LCD in 8 bit mode. So far we just succeeded to show characters only on second display and our efforts to use first "Enable" shows nothing!

According to the sprufm0b document Table-3 , we used LCD_MCLK for Enable on first display and LCD_PCLK for Enable on second display. (LIDD_CTRL[2:0]=100)

There is also a mismatch on Table 1 and Table 3 in sprufm0b document as listed below:

Signal Description on Table 1 Description on Table 3 (Character Display)
LCD_PCLK  LIDD character: not used Enable Strobe (first display)
LCD_MCLK  LIDD character: Secondary enable strobe Enable Strobe (second display optional)
LCD_AC_ENB_CS  LIDD character: Primary enable strobe Not Used

Is there anything needed to be modified?

LCD_RASTER_CTRL			&= 0xfffffffe;		// Turn raster controller off
LCD_LIDD_CTRL			= 0x0000000C;		// LIDD mode 0x4
LCD_LCD_STAT			= 0x000003ff;		// Clear status bits
LCD_LCD_CTRL			= 0x00002500;		// PCLK = 150MHz / 37 = 4.054 MHz, LIDD mode
LCD_LIDD_CS0_CONF		= 0xF7DCE3BA;

  • Hi,

    Which Processor SDK is this: RTOS or Linux? Which version?

    Best Regards,
    Yordan
  • Hi Yordan

    It's bare metal. No OS is used.

  • Ok, in this case if you use character LCD in 8-bit mode, have you tried the settings described in Table 24-3. LIDD I/O Name Map from the device Technical Reference Manual (www.ti.com/.../spruh77c.pdf )?

    Best Regards,
    Yordan
  • Hi Yordan

    Sorry to reply late. Yes we are using this setting but we did not succeed. in controlling both displays with OMAP-L138.
    We turn around this problem by using a GPIO and multiplexer to enable the other character LCD. We may face degrading in performance if we call some process hungry tasks. Meanwhile we are trying to integrate it in SYS/BIOS.
    I think no one has ever came with this issue and also no one in TI has tested it.

    Best Regards
  • Hi,

    To my knowledge this is not integrated in SYS/BIOS and not tested.

    Best Regards,
    Yordan
  • Hi Yordan

    I did not talk about problem with SYS/BIOS.

    My problem was simple:
    A) 2 LIDD displays won't work and it seems you guys have no idea about it.
    B) Mismatch in the tables I've mentioned in the first post.

    Best Regards
  • Hi,

    OMAP-L138 supports only one display controller at a time: The LCD controller consistsof two independent controllers, the Raster Controller and the LCD Interface Display Driver(LIDD) controller. Each controller operates independently from the other and only one of them is active at any given time.

    It should be doable to use the CS0 & CS1 for dual display, see Table 24-3. LIDD I/O Name Map in the TRM I pointed. However you should configure both LIDD_CS0_CONF & LIDD_CS1_CONF registers, not just LIDD_CS0_CONF.
    There is no OMAP-L138 reference design using two LIDD displays, so this hasn't been tested out completely and there is no sw configurations for this use case.

    Best Regards,
    Yordan
  • Hi Yordan

    I've read that section on TRM more than a dozen times. It doesn't work. So we've used 2 GPIO to control both Enables of the character LCD. We've managed it in the software. Maybe we missed something. I'll give it another try and update the post for reference.

    Best Regards

     

  • Ok, closing this for now. You can reopen it by posting on the thread.

    Best Regards,
    Yordan