Older boards, like Arduino UNO R3, do not have enough RAM to render a full screen image. A technique called "paging" lets us get around this issue.
Instead of storing the full image in RAM, we only use enough memory to hold a small region. The full image is rendered, but any pixels that fall outside this region are ignored. This rendered region is transferred to the Display's on-board memory. The process is then repeated for a different region, re-using the same RAM on Arduino, until the whole screen has been calculated, piece by piece.
If you have a more powerful board (ESP, SAMD21), the library won't bother paging. Your image will be calculated once, and once only, at full speed.
If your Arduino is paging to compensate for low RAM, or you wish to re-enable paging on a newer board, most displays allow you to set the optional page_height argument in your constructor.
DEPG0150BNS810 display(dc, cs, busy, page_height); For Uno R3, the default value is 20, meaning the display is calculated 20 rows at a time. Higher values use more RAM.
Attention ATmega2560 users:
- Paging is used for 3-Color displays: insufficient RAM.
- 2.9" displays use 60% of ATmega2560's RAM. If this in unacceptable, enable paging by setting a
page_heightin your constructor.