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Last Post 25 Feb 2009 09:26 AM by  johnlongawa
Problem with interfacing LCD
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zyzyis@gmail.com



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24 Feb 2009 03:03 PM
    Hi all,


    I got some problems with interfacing my samsung LCD on the litekit. I need the LCD_OE_ACD signal for data enabling. And as far as I know, the LCD_OE_ACD signal is not muxed by other signals, which means I can get the data directly from the header on J15:74 on the expansion board. But from both experiments and the litekit schematics, the LCD_OE_ACD is muxed by the up_GPIO_5 pin, and the board uses GPIO as default. I can't find any documents about the control registers to change it back to LCD_OE_ACD. Does anyone know which register controls the GPIO and LCD_OE_ACD? And how I can switch it back to LCD_OE_ACD? thank you very much.

    - zyzyis

    johnlongawa



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    25 Feb 2009 09:26 AM
    Since the baseboard is made for multiple SOM modules, the baseboard numbering of GPIO signals is different from that of the i.MX27. The i.MX27 signal "OE_ACD" goes from pad D3 to pin J1:38 on the SOM where it is called LCD_OE_ACD. The corresponding port pin on the '27 is PA31. You configure it as an output enable signal by clearing bit 31 in both the GIUS_A and GPR_A registers. If you are basing your port on the MX27ADS code then this is already being done for you in the "gpio_lcdc_active" function:


    gpio_request_mux(MX27_PIN_OE_ACD, GPIO_MUX_PRIMARY);


    You'll notice that the LCD output enable signal on the ZoomLite baseboard is not present on the connector to the LCD because the SHARP panels can operate without the OE signal. On the SHARP VGA panel the OE signal is called ENAB and can optionally be tied low. It might worth checking whether it is optional on the Samsung panel as well.

    Good luck.

    -john
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