Vertical mode? about adafruit-pcd8544-nokia-5110-lcd-library HOT 2 CLOSED

You are correct in that sending 0x20 will put the display in horizontal addressing mode and 0x22 in vertical mode. 0x20 is the function set register and 0x02 is the bit that switches to vertical mode.

When switching mode, it does not affect what is currently on the display. It only affects where the next byte will be drawn.

The pcd8544_buffer in the library is storing the image in horizontal mode and display() loops over the 6 pages (each 8 rows tall) and writes up to 84 bytes (one per column) before moving to the next page. Each byte represents 8 vertical pixels. Partial updates is why they don't just set the x,y address to 0,0 and spi write the entire buffer.

I don't believe there are any cheap clones of the display. I've seen the same LCD wrapped in the same metal case on various coloured PCBs from various vendors. They have subtle differences in their backlight LEDs but are otherwise seemingly identical.

If you want to see the horizontal / vertical addressing in action, try setting the x,y position to 0,0 then spi writing a single byte 0xff, pause and repeat. In both modes, each write will draw 8 vertical pixels. It's not possible to draw a row of 8 horizontal pixels from a single byte. They are always drawn vertical.

from adafruit-pcd8544-nokia-5110-lcd-library.

closing cause it seems to work?

from adafruit-pcd8544-nokia-5110-lcd-library.