I was taking the advantage of an existing piece of hardware (RepRapDiscount Full Graphic Smart Controller) for my present project.

Here is a link for the RepRap wiki about the controller

#define LCD_PIN_SCLK   A4
#define LCD_PIN_MOSI   6
#define LCD_PIN_CS   8
U8GLIB_ST7920_128X64_1X u8g(A4,6,8, U8G_PIN_NONE);

But all I got is a blank screen with no light at all. What has happened?


I solved the problem myself. It turns out to be a problem of wrong pinouts.

My PCB of the project was originally designed for the LCD2004 counterpart, and I thought it was a drop-in replacement for 12864. But no, it's not.

RAMPS Smart Adaptor 12864 vs 2004 This is the "Smart Adaptors". Notice that the orientation are 180 degree different.

If you have the same problem not lighting up a 12864 when switching from 2004, or vice versa. Check your orientation as above.

My solution will be crimping a different JTAG wire instead.


I had a similar issue with figuring out how to get the Zyltech.com RepRapDiscount Full Graphic Smart Controller (with their Mega 2560 clone) to work with u8glib. After some fiddling it looks like the correct settings for me were:

// SPI Com: SCK = en = 23, MOSI = rw = 17, CS = di = 16
U8GLIB_ST7920_128X64_1X u8g(23, 17, 16);

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