title	layout
Sharp DRM Driver	default

Sharp Memory LCD Kernel Driver

DRM kernel driver for 2.7" 400x240 Sharp memory LCD panel.

User Guide

This is a kernel device driver to provide a display device to the Linux kernel.

Font Configuration

This module automatically adds contents to the Raspberry Pi /boot/firmware/cmdline.txt to configure the Linux framebuffer, including font size.

The option fbcon=font:VGA8x8 configures default font to a smaller size, resulting in dimensions of 30 rows and 50 columns. Can be changed to font:VGA8x16 for a larger font. More fonts and options for the fbcon module can be found at https://www.kernel.org/doc/Documentation/fb/fbcon.txt

monoset Utility

The monoset script in this repo is a helper to tune the monochrome cutoff for an application. It is installed by default on Beepy Raspbian. If an application has problems with monochrome color, you can run

monoset [0 .. 255] <command>

The default driver monochrome cutoff is 32. Setting a value of 0 will cause the whole screen to display on, and 255 to display off.

For example, the nmtui utility works best with a cutoff of 127. In the default Beepy Raspbian profile, there is an alias

alias nmtui="monoset 127 nmtui"

This will automatically apply a cutoff of 127 when nmtui is started from the shell. You can add your own aliases to your profile at ~/.profile.

Module Parameters

Several options are exposed in the directory /sys/module/sharp_drm/parameters/. Run

echo <setting> | sudo tee /sys/module/sharp_drm/parameters/<param>

To make changes persistent:

• Add sharp_drm=<param>:<setting> to /boot/firmware/cmdline.txt

• Edit the file /etc/modules and change the line sharp-drm to sharp-drm <param>=<setting>

• auto_clear: 1 to blank the screen when the display driver is unloaded (default enabled). If disabled, screen contents will remain until power is removed.

• mono_cutoff: Consider all pixels with one of R, G, B below this threshold to be black, otherwise white (default 32)

• mono_invert: 0 for white-on-black, 1 for black-on-white. Can be toggled on-device by pressing Berry, then Zero (Meta mode + 0). For more information on Meta mode keymappings, see [https://github.com/ardangelo/beepberry-keyboard-driver/README.md]

• overlays: 0 to disable overlays (default enabled). Not recommended to disable, overlays are used to display modifier key state and key reference overlays

Developer Reference

Building from source

Install the Linux kernel headers

sudo apt-get install raspberrypi-kernel-headers

Build, install, and enable the kernel module:

make
sudo make install

To remove:

sudo make uninstall

Original fbdev module readme with pinouts and build instructions

References

Original SPI and GPIO kernel driver at:

https://github.com/w4ilun/Sharp-Memory-LCD-Kernel-Driver

Sharp datasheet:

https://www.sharpsde.com/fileadmin/products/Displays/2016_SDE_App_Note_for_Memory_LCD_programming_V1.3.pdf