Posted on behalf of @caimano — the research, testing and write-up are all theirs.
Technical case study by Fabio Celli / Caimano — IT Consultant · July–August 2026
Experimental validation — not an official Sharp/NEC upgrade certification.
Objective: extend the operational life of approximately 50 NEC V404-RPi professional displays while retaining the original display and carrier board, updating the software stack, and assessing a possible hardware upgrade to the Compute Module 4S.
Result at a glance
Two paths were validated:
- Keep the original Compute Module and upgrade to Raspberry Pi OS Trixie 64-bit Lite + a modern 2026 Anthias release, resolving DRM video detection.
- Experimentally install a Raspberry Pi Compute Module 4S on the original NEC carrier — boot, network, eMMC, Anthias and 1920×1080 display all operational.
| Item | Outcome |
|---|---|
| Original platform | NEC V404-RPi + NEC Compute Module Interface Board DS1-IF10CE + Compute Module 3 NEC Edition |
| Main issue | CM3 performance now limited, and black screen after installation with the new DRM/KMS stack |
| Video fix | video=HDMI-A-1:1920x1080M@60D in /boot/firmware/cmdline.txt |
| Hardware upgrade tested | Raspberry Pi Compute Module 4S Rev 1.0 |
| Outcome | Positive in the tests performed; configuration not officially certified by Sharp/NEC |
Context: a display fleet that still has value
The project originated from managing a digital signage infrastructure consisting of approximately 50 NEC MultiSync V404-RPi displays. The displays continue to meet operational requirements in terms of panel performance and image quality; the hardware limitation that gradually emerged was the embedded computer, based on the Compute Module 3 generation, while the software limitation was that after installing the new Anthias release, the display remained black and showed no image.
The objective was therefore to separate the obsolescence of the compute module from the useful life of the monitor: first by verifying the feasibility of a complete software upgrade, then by experimenting with a hardware upgrade while retaining the original NEC carrier/interface board.
Figure 1 — Rear access to the Raspberry Pi module integrated into the NEC display.
Identification of the original hardware
Opening the unit and photographically documenting the hardware made it possible to identify the carrier board and the original Compute Module. NEC’s 2019 documentation lists the V404 among the displays compatible with the NEC Compute Module Interface Board DS1-IF10CE and identifies the 16 GB CM3 NEC Edition (RPi3CM16G) among the supported modules.
Figure 2 — NEC carrier/interface board: component side and Compute Module SODIMM connector. PCB marking
715G7967-T0F-000-005K is visible.
Figure 3 — Rear side of the NEC carrier; detail of PCB revision
715G7967-T0F-000-005K.
Figure 4 — Detail of the Kingston
EMMC16G-M525 eMMC on the NEC Edition Compute Module: 16 GB onboard.
Documentary evidence
The NEC “Raspberry Pi Compute Module Setup Guide” specifies for the V404: DS1-IF10CE carrier, 16 GB CM3 NEC Edition, and operating-system programming via the display’s USB Boot mode.
Four parallel lines of investigation
To avoid unsupported assumptions, the investigation was conducted on four fronts: official NEC/Raspberry Pi documentation, the Raspberry Pi technical community, the Anthias/Screenly technical community, and NEC/Sharp European support. This made it possible to clearly distinguish what was documented, what had been evaluated by the manufacturer, and what needed experimental validation.
- NEC/Sharp documentation — DS1-IF10CE architecture, USB Boot, GPIO, internal HDMI, and V404 support.
- Raspberry Pi — official CM4S specifications and its explicit targeting of industrial customers migrating from CM3/CM3+.
- Raspberry Pi Forum — public technical discussion on replacing the CM3 with a CM4S in the NEC carrier.
- Anthias/Screenly Forum — technical discussion, with posts and reports of the bugs and anomalies found during testing.
- Sharp/NEC Europe — first- and second-level tickets with specific compatibility questions.
Open the technical thread on the Raspberry Pi Forum
Sharp/NEC Europe ticket: questions submitted
On 11 July 2026 a formal technical inquiry was sent to Sharp/NEC Display Solutions. The case was registered as Ticket #9472747. The stated context was a fleet of approximately 90 still-functioning V404-RPi units, with the need to avoid replacing complete displays solely because of the limitations of the embedded module.
- Is the Raspberry Pi Compute Module 4S electrically and mechanically compatible with the carrier installed in the V404-RPi?
- Has Sharp/NEC ever tested or validated the CM4S on this platform?
- Was an updated carrier or another official upgrade solution ever developed?
- Which carrier board, part number and hardware revision are installed in the V404-RPi?
- Are there engineering notes, service manuals or compatibility documents relating to the carrier?
Timeline — European support
11/07/2026 Ticket #9472747 opened → 13/07 photographs of the internal hardware sent → 14/07 reply from the Senior Product Manager → 15/07 technical reply with specific guidance → 21/07 formal forwarding of the second-level response by the Sharp Service Team Germany.
Sharp Product Management response
On 14 July 2026, the Senior Product Manager for Large Format Displays & Computing Technologies provided a particularly significant historical detail: during development of earlier Raspberry Pi solutions, hardware evaluations had been carried out to determine whether the Compute Module 4 family could be supported on the existing platform.
Key point from the response
Sharp reported that hardware compatibility testing had shown promising results and indicated technical feasibility. However, the project was not taken through to an official commercial offering: firmware, software, validation and long-term support were not completed to the required level, in a context of limited development resources and changing product priorities.
This point is important: the correspondence does not describe the CM4S as technically impossible on the V404-RPi; rather, it describes a path that was never turned into an officially supported upgrade route.
Second-level technical response
On 15 July the most operational response arrived. Support stated that it could not confirm the combination with 100% certainty, and recommended testing a single CM4S before any rollout across all displays.
| Question | Response received | Implication |
|---|---|---|
| CM4S electrical/mechanical compatibility? | Yes | Physical testing on the original carrier can proceed. |
| CM4S officially validated on the V404-RPi? | No | Local experimental validation required. |
| Updated carrier / official kit? | No | No commercial retrofit path available. |
| Recommendation | Test a single module first | Approach adopted in the project. |
Why the CM4S was the right candidate
Raspberry Pi documentation is particularly explicit: the Compute Module 4S retains the DDR2-SODIMM form factor of the CM1/CM3/CM3+ generations and is specifically intended for industrial customers migrating from Compute Module 3 or 3+. The official datasheet also lists a BCM2711 quad-core Cortex-A72, LPDDR4 memory, and larger, faster eMMC options.
Figure 5 — Raspberry Pi Compute Module 4S. Product image used in the project.
Raspberry Pi — official Compute Module 4S page
Raspberry Pi — Compute Module 4S Product Brief (PDF)
Before the hardware upgrade: modernizing the CM3
Before replacing the module, the possibility of fully upgrading the already installed CM3 was tested. Raspberry Pi OS Trixie 64-bit Lite was prepared and the new-generation Anthias installed. The operating system completed boot, regularly obtained an IP address, and was reachable via SSH.
$ systemctl is-system-running
running
$ systemctl --failed
0 loaded units listed.
Despite this, the NEC display remained black. Distinguishing between “a non-functioning system” and “only the video path not being initialized” was the decisive diagnostic step.
Diagnosing the DRM/KMS issue
Anthias was correctly installed and the containers were active, but the viewer continued waiting for a display. A direct check of Linux DRM confirmed that HDMI-A-1 was reported as disconnected.
anthias-viewer: start_viewer: no display connected yet — waiting.
/sys/class/drm/card0-HDMI-A-1/status: disconnected
vc4-drm soc:gpu: [drm] Cannot find any crtc or sizes
The NEC carrier routes the video signal internally to the display. With Trixie’s modern DRM/KMS stack, automatic detection did not correctly report the monitor as present, even though the operating system, network and Anthias were fully operational.
Topic on the Anthias forum: New Anthias on TV NEC V404 — black screen
The solution on the NEC: explicit HDMI port initialization
The solution was to add a kernel parameter to the single line in /boot/firmware/cmdline.txt, forcing the DRM HDMI-A-1 connector to the display’s native resolution.
video=HDMI-A-1:1920x1080M@60D
Fix result
After rebooting,
/sys/class/drm/card0-HDMI-A-1/statuschanged fromdisconnectedtoconnected. Anthias began playing assets on the NEC. The NEC guide specifies 1920×1080 as the recommended video resolution for the platform.
$ cat /sys/class/drm/card0-HDMI-A-1/status
connected
Functional validation on the CM3
Testing did not stop at simply obtaining an image. The main digital signage functions and the behaviour after reboots and shutdowns were tested.
| Test | Result |
|---|---|
| Image assets | OK |
| URL assets / web content | OK |
| Video assets | OK |
| Landscape | OK |
| Portrait | OK |
| Reboot | OK |
| Forced shutdown and subsequent power-on | OK |
| Anthias GUI over network | OK |
First milestone
The V404-RPi can continue operating with the original Compute Module, Raspberry Pi OS Trixie 64-bit Lite and modern Anthias — provided that DRM initialization of the internal HDMI path is handled correctly.
Preparing repeatable images
Once the fix had been identified, the Trixie image was customized by directly modifying cmdline.txt in the boot partition. In parallel, a golden-image strategy was defined: start from an actually installed, configured and validated Compute Module, then capture a complete image for controlled deployment.
Figure 6 — Mounting the Raspberry Pi OS image boot partition for controlled modification of
cmdline.txt.
The golden image is kept on DHCP to avoid conflicts during deployment; static addresses, where required, are assigned later on the individual NEC units.
Installing and testing the Compute Module 4S
After software validation on the CM3, a single CM4S was installed on the original carrier, following exactly the caution suggested by second-level support: one pilot device, thorough testing, and no advance rollout.
The system completed installation of Trixie and Anthias; the same DRM parameter required for the NEC video path was applied. The module was identified by the system as Raspberry Pi Compute Module 4S Rev 1.0.
Figure 7 — Anthias Live Diagnostics on the NEC with CM4S: detected model, 1920×1080, approximately 4 GB RAM, and operational eMMC storage.
$ cat /proc/device-tree/model
Raspberry Pi Compute Module 4S Rev 1.0
$ free -h
Mem: 3.6Gi total 696Mi used 2.9Gi available
CM4S upgrade result
In the tests performed, the CM4S operated on the original NEC carrier with network, eMMC, operating system, Anthias and video output. The same functional tests previously carried out on the CM3 were repeated.
| Test | Result |
|---|---|
| System boot and startup | OK |
| Ethernet | OK |
| eMMC | OK |
| Anthias server/viewer | OK |
| Display 1920×1080 | OK |
| Images, URLs and video | OK |
| Landscape / portrait | OK |
| Reboot and power cycle | OK |
| Improved performance | OK |
Experimental validation
The test confirms technical feasibility on the specific hardware combination used. It does not, however, turn the CM4S into an officially Sharp/NEC-certified upgrade — this distinction remains essential for any production deployment, even though the tests confirmed full compatibility in the tested configuration.
What was discovered along the way
| Finding | Meaning |
|---|---|
| The black display did not indicate a crash | Linux, systemd, network, Docker and Anthias were operational: the issue was isolated to DRM. |
| The CM3 can still be used | Trixie 64-bit Lite and modern Anthias are operational after the HDMI/DRM fix. |
| CM4S is designed for industrial CM3/CM3+ migrations | This is stated explicitly in the Raspberry Pi documentation. |
| Sharp had evaluated the CM4 family on the platform | The Product Management response reports promising hardware results, but no completed official product. |
| Second-level support confirmed electrical/mechanical compatibility | With the necessary caution: no 100% official validation of the V404-RPi + CM4S combination. |
| The real-world test closed the loop | The single pilot CM4S completed boot, networking, Anthias and video output on the V404-RPi. |
A broader project conclusion
The correspondence with Sharp allows for a balanced interpretation of the story. The possibility of moving the platform toward CM4-generation hardware had been evaluated internally and had shown promising technical signs, but it did not reach the stages required to become a supported commercial offering. In the meantime, product priorities shifted toward newer, more standardized platforms.
This project revisited that possibility in a real operational environment, without claiming to replace manufacturer validation, and took it through to a documented functional test. The value lies not merely in getting a CM4S to boot, but in reconstructing the diagnostic path and the conditions required for the entire chain — boot, network, containers, viewer, DRM and display — to operate correctly.
The technical achievement
Avoid declaring an entire professional display obsolete simply because the small computer inside it has aged. The result opens two concrete possibilities: continue using the CM3 with modern software, or significantly increase computing capacity with the CM4S while retaining the original display and carrier.
Final status
| Function | Updated CM3 | Pilot CM4S |
|---|---|---|
| Raspberry Pi OS Trixie 64-bit Lite | OK |
OK |
| Modern Anthias | OK |
OK |
| Ethernet / SSH | OK |
OK |
| DRM 1920×1080 | OK with fix |
OK with fix |
| Images / URLs / video | OK |
OK |
| Landscape / portrait | OK |
OK |
| Reboot / power cycle | OK |
OK |
| Official CM4S support on V404 | — |  No — positive experimental test only |
Original documentation and references
The following links lead to the original sources used in the investigation. Where available, the manufacturer’s official source is preferred.
- NEC — Raspberry Pi Compute Module 3+ / NEC Edition datasheet (PDF)
- Raspberry Pi — Compute Module 4S product page
- Raspberry Pi — Compute Module 4S Product Brief (PDF)
- Raspberry Pi — Compute Module 4S Datasheet (PDF)
- Raspberry Pi — Compute Module hardware documentation
- Raspberry Pi Forum — the project’s technical thread
- Anthias Forum — New Anthias on TV NEC V404: black screen
- Sharp Display Solutions Europe
Reference NEC document
The “NEC Raspberry Pi Compute Module Setup Guide” (2019) was used as the reference for DS1-IF10CE, V404, USB Boot, HDMI/CEC, GPIO and recommended resolution. A copy of the PDF was available in the project documentation; the document is cited in this case study even though a stable public URL identical to the archived copy is not available.
Methodological note and limitations
The conclusions regarding the CM4S derive from tests performed on the specific NEC V404-RPi unit and carrier identified in the project. They do not constitute certification of universal compatibility and do not replace manufacturer guidance. Before any large-scale rollout, prolonged stability, temperature, power-cycling, real-asset, network and recovery-procedure testing is recommended.
The organisational or commercial reasons that led Sharp/NEC not to complete an official upgrade are reported strictly in the terms contained in the correspondence received: limited development resources and shifted product priorities. No further undocumented causes are attributed.
Acknowledgements
Thanks are due to the technicians and managers at Sharp Display Solutions Europe / NEC who retrieved information on a platform that no longer belongs to the current product generation; to the Raspberry Pi Community users who contributed to the technical discussion; and to the Anthias/Screenly team, whose work proved essential in enabling the hardware to be tested with improved, functional digital signage software. The final result stems from the combination of official documentation, technical support, community input and experimental field validation.
Objective achieved
NEC V404-RPi · Trixie 64-bit Lite · Anthias 2026.07.4 · CM3 / CM4S · DRM 1920×1080
Fabio Celli / Caimano · 2026 · Experimental validation — not an official Sharp/NEC upgrade certification.