No display on bookworm

[zedstarr]

No display after following the instructions contained herein and referenced in the youtube videos when running bookworm-based Raspberry Pi OS.

I have found this DRM based driver https://github.com/sqfmi/Sharp-Memory-LCD-Kernel-Driver but have not yet tried it...

[zedstarr]

I tried to compile this on a 6.12 kernel (with headers) and fixed a couple of minor errors but seem to be stuck now at a missing header file in the Pi's tree (/usr/src/linux-headers-6.12.47+rpt-common-rpi/include/drm/drm_fbdev_generic.h) required to satisfy the "implicit declaration of function ‘drm_fbdev_generic_setup’" error by adding an include #include <drm/drm_fbdev_generic.h>

Fixed "too few arguments to function ‘drm_fb_xrgb8888_to_gray8’" by adding struct drm_format_conv_state state = { 0 }; near the top of the function and changing
drm_fb_xrgb8888_to_gray8(&dst, NULL, &vmap, fb, clip);
to
drm_fb_xrgb8888_to_gray8(&dst, NULL, &vmap, fb, clip, &state);

Fixed "‘drm_gem_simple_display_pipe_prepare_fb’ undeclared here" by removing the following line from the struct intialisation
.prepare_fb = drm_gem_simple_display_pipe_prepare_fb,

[asmagill]

Ok, here is how I got the display working for Trixie, lite 64bit for a Pi Zero 2:

First, I cloned the repository at https://github.com/Kiboneu/sharp-drm-driver

Modify sharp-drm.dts as follows:
around line 30, replace brcm,pins = <23 22>; with brcm,pins = <25 24>;
around line 49, replace vcom-gpios = <&gpio 23 0>; with vcom-gpios = <&gpio 25 0>; and disp-gpios = <&gpio 22 0>; with disp-gpios = <&gpio 24 0>;.

Now follow the github site instructions: make and sudo make install
Finally, before rebooting, edit /boot/firmware/config.txt and change dtparam=spi=on with dtoverlay=spi0-1cs,cs0_pin=23,nomiso=1

Now, reboot.

I'm going to play with it some more and will try to put up my own fork sometime later this week... I'd kinda like to see about setting it up to use dkms so we don't have to rebuild the module for each kernel upgrade (at least until upstream kernel developers change the api interface yet once again <sigh>)

[andypiper]

wow, thanks for sharing! I'm going to take a look at testing this later. Thanks for your work.

[zedstarr]

Thanks, I started again with a fresh trixie image and got the display working using the repo above and your instructions :-)

Seems to want to stick to default white-on-black though...

After boot/login using echo 1 | sudo tee /sys/module/sharp_drm/parameters/mono_invert will flip to black-on-white but editing the files as described (adding sharp_drm=mono_invert:1 to /boot/firmware/cmdline.txt and sharp_drm mono_invert=1 to /etc/modules) has no effect

logs show:
kernel: Unknown kernel command line parameters "sharp_drm=mono_invert:1", will be passed to user space
and
systemd-modules-load[287]: Failed to find module 'sharp-drm mono_invert=1'

Even creating a file /etc/modules-load.d/sharp_drm.conf containing mono_invert=1 has no effect

[asmagill]

I created a file named /etc/modprobe.d/sharp-drm.conf and put in this line:

options sharp-drm mono_invert=1

Or, you can do from any terminal:

echo 1 | sudo tee /sys/module/sharp_drm/parameters/mono_invert

Upon re-reading, you already know this...

[asmagill]

Lines in /etc/modules or files in /etc/modules-load.d are just lists of modules to load at boot time; options for modules (both those loaded at boot and those loaded by the user at other times) get put into files in /etc/modprobe.d.

[andypiper]

Discoveries:

• 32-bit lite Raspberry Pi Trixie didn't seem to have kernel-headers (?)
• 64-bit lite does, installed by default

Compiled per instructions; on reboot, I'm seeing the display activate (and module is loaded); but I'm never getting any text output shown on screen. Did I miss a config option?

(I'll also note that, given my initial efforts to get this thing working included having the pins on the Pi Zero the wrong way before realising I needed to have them reversed, and various other things I've tried in software, there's a small chance I messed up the display somewhere along the line...)

[asmagill]

Is the yellow LED underneath the screen turning on? If so, you need to go back and recheck that you made the appropriate changes to sharp-drm.dts because that is GPIO 22, which is not used by our Sharp display.

If the LED isn't turning on, make sure that the spi line has been corrected in /boot/firmware/config.txt (you may have dtparam=spi=on in there twice -- once at the top which may or may not be commented out which is included as part of the default installation, and a second time at the bottom right above the dtoverlay=sharp-drm line which was added by sudo make install -- both need to be deleted or commented out, and the correct line dtoverlay=spi0-1cs,cs0_pin=23 put right above the sharp-drm line (I'm not as positive about the nomiso=1 parameter -- the display doesn't use it, but according to the schematics, the rfm95 radio might -- I need to play around some more -- leaving nomiso=1 out won't cause a problem, it will just mark a gpio pin as in use that might have been free otherwise.)

Finally, I'd check to make sure the /boot/firmware/cmdline.txt file ends with fbcon=font:VGA8x8 fbcon=map:10

[andypiper]

thanks for the extra pointers - I'll have another poke tomorrow!

[asmagill]

Fwiw, using a continuity tester, I can confirm that the radio module we have is only using the Pi's TX and RX pins -- no SPI pins are connected (though they are broken out to the pads on the right of the radio module when looking at the SharpiKeebo's back). So, including nomiso=1 in the spi overlay will free up a pin for other uses (it's broken out in the pads on the board underneath the Pi header) if you want it.

[andypiper]

overall feels like this board was never really tested for any kind of the uses it was described for 🤷🏻

[talmage]

How do I fix this error that occurs when I compile the sharp-drm-driver?

ERROR: modpost: "drm_fbdev_ttm_setup" [/home/talmage/git/sharp-drm-driver/sharp-drm.ko] undefined!

Installing libdrm-dev didn't fix the problem.

For reference, I'm using Raspian Trixie Lite (unless one of the apt upgrades changed it).

uname -a reports Linux sharpikeebo 6.12.47+rpt-rpi-v7 #1 SMP Raspbian 1:6.12.47-1+rpt1 (2025-09-16) armv7l GNU/Linux

[asmagill]

Look like you're using the 32bit version of Trixie? Haven't tried that yet -- I'm using the 64bit one.

I'll try to give the 32bit version a shot tonight, unless someone else has already figured it out?

[asmagill]

You could try https://github.com/ardangelo/sharp-drm-driver -- the repo I give above is forked from it, and the main change was to migrate from drm_fbdev_generic_setup to drm_fbdev_ttm_setup... maybe the 32bit kernel is lagging the API change?

At any rate, I'll let you know if I figure something out tonight.

[talmage]

Look like you're using the 32bit version of Trixie? Haven't tried that yet -- I'm using the 64bit one.

That's right. I started this adventure on a Pi Zero and I'm using the same SD card to boot my Pi Zero 2. I'll try the 64-bit version of Trixie. I'm fine with that.