A Waveshare ESP32-S3-RLCD-4.2 board combines a 400x300 RLCD display, ESP32S3 with PSRAM, ES8311 audio codec, speaker, two I2S microphones, and Li-ion charging plus 18650 holder.
The project turns it into an internet radio that boots onto Wi-Fi, syncs time via NTP, loads stream URLs from flash, and serves a setup web page in the background.
The 4.2-inch display drives a 32-bar spectrum analyser at 240 MHz over SPI, with the display running at 40 MHz.
That setup reaches about 35 FPS and produces a visibly cool audio visualizer.
Pushing SPI speed too far causes misfiring pixels and artefacts, and the display starts to 'scream' around 60 MHz.
An interesting PCB with a 400x300 RLCD display, ESP32S3 with PSRAM, ES8311 audio codec, speaker, two i2s microphones and li-ion charging circuit and 18650 cage can be purchased on a well-known Chinese portal and more.
https://docs.waveshare.com/ESP32-S3-RLCD-4.2 You can do many different projects on this. The first thing I did was an audio stream player from the internet - commonly referred to as an 'internet radio'.
Programming this device is great fun and allows you to learn a lot. So, quickly - the device, when switched on, is supposed to connect to the wifi network, download the time from the NTP server, read the list of stream addresses from the flash and immediately play the last selected station, and in the background, host a simple web page where you can configure the wifi and stream addresses for yourself. As the display is quite large - 4.2" I decided to stuff a 32 bar audio spectrum analyser in there, ESP driven at 240 MHz, SPI to the 40 MHz display and managed to get about 35 FPS on this analyser and it looks pretty cool. I'm sharing all the code with all the libraries used etc - zipped up the whole platform project in Visual Studio. I took the opportunity to check how it feels to do the 'interfaces' to the displays using SquareLine Studio - and it's quite convenient, I was previously 'sculpting' everything by hand. In the video you can see misfiring pixels, artefacts - but that's because I recorded it while experimenting at SPI speed - and this display "starts to scream" at around 60 MHz.
There is a firmware.bin file in the .pio directory that can be uploaded straight to the ESP without compiling the sources, when you turn it on the device will not find the saved network and will create its own, the rest of the instructions will be on the screen.
Anyone have any ideas what else can be programmed on such a gadget?
Attachments:
RLCD_PLAYER.7z(46.8 MB)
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It looks great. The RLCD doesn't provide for backlighting?
It has built-in microphones, I wonder if it would be possible to do local voice control of home functions? Once integrated with some LLM, you could make your own agent with verbal interaction + display.
Very cool, price over 100PLN, so you need to have a more concretised application I immediately think of some notification display, some text output from ChatGPT
But let's give the "expert" a voice @ElektrodaBot suggest what the board can be used for, split into hobbyist and commercialisation ideas for the European market.
Analyse what may be missing in the European market, what such a respectively software ESP32S3 + RLCD 4.2" board with given functionality can offer.
Present a report.
Very cool, price over 100PLN, so you need to have a more concrete application I immediately think of some notification display, some text output from ChatGPT
But ...
Report: ESP32-S3 + RLCD 4,2" as a hobby and product platform for the European market
Short conclusion
This board is most interesting not as "another ESP32 with a screen" but as a small, low-power audio-visual terminal : screen visible as "paper", Wi-Fi/BLE, microphones, speaker, RTC, temperature/humidity sensor, TF card and power from 18650. This naturally points it in the direction of:
- home Assistant / MQTT panels, - local voice assistants, - desktop notification terminals and LLMs, - information boards, - simple HMI for industry, service, warehouse, photovoltaics, HVAC, - privacy-first devices in compliance with the spirit of European regulations.
Waveshare describes this board as an AIoT module with a 4.2" RLCD screen, Wi-Fi/BLE, ESP32-S3-WROOM-1-N16R8, 16 MB Flash, 8 MB PSRAM, dual microphone, ES8311, SHTC3, RTC, TF slot and 18650 cage. The screen itself is 300 × 400 pixels, fully reflective and requires no backlight, and the manufacturer highlights the similarity to e-paper at faster refresh rates. ( docs.waveshare.com )
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1. Technical nature of the board
Major features
Features
Practicality
ESP32-S3, 240 MHz, PSRAM
Sufficient for GUI, audio, simple DSP, MQTT, HTTP, WebSocket, local wake-word
RLCD 4.2", 300 × 400
Very good daylight readability, no glare in the eyes, sensible text GUI
No backlight
Low power consumption, but no readability in the dark without external lighting
2 microphones + ES7210/ES8311
Possible AEC, noise reduction, local voice commands, voice terminal
Speaker
Alerts, acknowledgements, TTS, radio, service messages
SHTC3 + RTC
Environmental station, clock, calendar, data logging
Important note: RLCD is not an e-paper in the sense of bistability. Do not assume that the image "holds" without any power supply as in a typical E-Ink. The energy gain comes mainly from the lack of backlighting. For a battery product, you need to realistically measure the current consumption in the following modes: active Wi-Fi, audio, idle, deep sleep, screen refresh, listen to activation word.
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2. Hobby ideas 2
2.1 Notification terminal / "desk companion"
This is probably the most natural design after internet radio.
Features:
- notifications from your computer, phone or home server, - calendar, - task list - clock - weather, - home Assistant status, - status of servers, NAS, 3D printer, VPN, router, - quickview of news from the local LLM.
Why this board fits:
- RLCD is suitable for static and semi-static content, - does not glow at night like OLED/LCD, - 4.2" screen already accommodates a sensible text layout, - audio can be used for discrete alarms.
Practical example: the device stands by the monitor and shows only relevant events: "3D printing completed", "UPS switched to battery", "garage door open", "meeting in 10 minutes".
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2.2. Frontend to ChatGPT / local LLM
The idea of "text output from ChatGPT" is a very good one, but I would architecturally separate it:
- ESP32-S3 : screen, microphones, speaker, buttons, wake-word, communication. - Local or cloud server : STT, LLM, TTS.
The ESP32-S3 is not a sensible platform for running full LLM or full Whisper. It can, however, act as a very good terminal:
1. detects the local activation word, 2. records a short speech, 3. sends audio or text to the backend, 4. receives a reply, 5. displays it on the RLCD, 6. optionally plays the TTS through a loudspeaker.
For more private applications, the backend could be a local PC, mini-PC, NAS or a Raspberry Pi of the higher end. Home Assistant itself indicates that a local STT/TTS can be done, but for a full Whisper it already recommends hardware of at least Intel N100 class or equivalent, especially with the requirement for reasonable responsiveness. ( home-assistant.io )
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2.3. Home Assistant local voice panel
This is, in my opinion, one of the best designs for this board.
Possible scenario:
- local wake-word on ESP32-S3, - commands via Home Assistant Assist, - MQTT for simple controls, - screen as room status: - temperature, - humidity - light, - blinds, - alarm, - presence, - recent events.
Espressif provides ESP-SR with WakeNet, MultiNet and AFE. MultiNet on the ESP32-S3 recognises multiple voice commands locally, according to the documentation up to 200 commands in the current description, and the ESP-SR repository also mentions models that support larger command sets. The AFE includes AEC, VAD, BSS and noise reduction, among others, which is a good fit for a board with two microphones. ( docs.espressif.com )
Practical architecture:
Code: text
Log in, to see the code
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2.4. Extended audio player
The author of the topic has already done internet radio with a spectrum analyser, so the direction is proven. This can be developed further:
- internet radio, - podcast player, - tF card player, - mPD client, - simple audio book player, - spectrum visualisation, - display of texts or transcriptions.
The RLCD at 35 FPS in the author's demonstration shows that the screen is not limited like a typical e-paper. This paves the way for smooth VU indicators, FFT spectrum, animated menus and scrolling text.
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2.5. Portable logger / service terminal
Very forum application:
- wi-Fi analyser, - mQTT monitor, - i2C sensor tester, - uART logger, - modbus terminal after RS485 connection, - cAN monitor after adding transceiver, - portable panel for testing PV systems, heat pumps, recuperation, CO controllers.
The 4.2" screen allows the data table, trend graph, connection status and error log to be displayed simultaneously.
This has more educational value than a simple ESP32 module with a small TFT, because it forces you to integrate multiple layers of the system.
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2.7. Doom?
As a demo: yes, it makes sense. ESP32-S3 + PSRAM, a fast screen relative to the e-paper and 400 × 300 pixels are enough for a "because Doom has to go on everything" class port. Commercially it doesn't matter much, but as a performance test of SPI, frame buffering and input control - a very good demonstration project.
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3. What is missing from the European market 3
3.1 Gap 1: local, private voice assistant with readable screen
The market has:
- cloud-dependent smart speakers, - tablets with LCD/OLED screens, - android-based wall panels, - voice-satellite for Home Assistant, - e-paper dashboards.
But what is missing is a low-cost, small connectivity device:
- local or hybrid voice processing, - a non-glowing screen, - low energy consumption, - readability in daylight, - simple integration with Home Assistant/MQTT, - no mandatory cloud account.
Home Assistant is developing the direction of private voice and its own Voice Preview Edition devices, but many applications still need an additional visual layer: home status, message, command list, action confirmation, graph or alarm. ( home-assistant.io )
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3.2 Gap No. 2: screen between e-paper and TFT
E-paper:
- great for infrequent changes, - very low consumption, - but slow, - poor for animations, menus, audio-visualisation.
TFT/OLED:
- fast, - colourful, - but lights up, - consumes more energy, - looks worse in bright sunlight.
The RLCD is in the middle:
- faster than e-paper, - less energy-consuming than a backlit LCD, - readable in daylight, - good for text, icons, simple graphs.
This is attractive for 'calm technology': devices that are constantly visible but not fighting for the user's attention.
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3.3 Gap No. 3: energy-efficient B2B terminals
Energy efficiency is growing in importance in Europe. EU regulations for standby and networked standby require increasingly lower power consumption, and from 2027 for devices in networked standby the limits depend on the product class and are in the range of 2-7 W. For normal standby/off states, the limits are even lower. ( energy-efficient-products.ec.europa.eu )
This creates space for devices of the type:
- hall plate, - station panel, - storage guide, - environmental monitor, - machine status panel,
which do not need a full Android tablet.
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3.4 Gap 4: privacy-first products compliant with EU regulations
It is not only CE and EMC that are becoming important for IoT equipment in Europe, but also cyber security, updates and data control. The Cyber Resilience Act covers digital products connected directly or indirectly to the network and enforces cyber security requirements through the product lifecycle; the European Commission indicates that manufacturers will have to bring compliant products to market by 2027 ( commission.europa.eu )
Additionally, the Data Act, applicable from 12 September 2025, strengthens the right of users to access and share data generated by connected devices. This is important for IoT devices, loggers, industrial panels and home sensors. ( digital-strategy.ec.europa.eu )
ETSI EN 303 645, on the other hand, indicates baseline practices for consumer IoT: no default passwords, a vulnerability reporting policy, software updates and personal data protection. This should be considered a design minimum for a commercial product. ( etsi.org )
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4. Commercialisation ideas in Europe
General ranking
Ideal
Potential
Risk
Evaluation
Local Home Assistant panel / MQTT with voice
high
medium
very good
Desk terminal LLM/notification
medium-high
medium
good
medium
Classroom/desk/position
high B2B
medium
very good
Storage/voice- terminalpicking
high B2B
high
good, but needs ruggedisation
Monitor energy / PV / HVAC
high niche
mediocre
very good
Senior Assistant
socially high
regulatory high
careful
Electronic price label
medium
high-priced
mostly niche only
Educational product / devkit with course
medium
low
good start
[/table:effa1e2597]
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4.1 Product A: Home Assistant private panel with voice
Description: Small panel to place on desk, shelf or stick to wall. Shows home status and accepts voice commands.
Functions:
- integration with Home Assistant, - MQTT, - local commands: light, blinds, heating, - dashboard screen, - voice messages, - night mode without light emission - notifications: bell, alarm, leak, washing machine, gate.
Market advantage:
- privacy, - no cloud as a requirement, - no glowing screen, - better feedback than in a smart speaker alone, - lower power consumption than a wall-mounted tablet.
For whom:
- home Assistant users, - smart-home installers, - small offices, - passive/energy-efficient homes.
Business model:
- finished device, - open-core firmware, - paid extras: integrations, enclosures, dashboard designer, - pRO version with RS485, Ethernet or PoE.
My rating: most natural direction.
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4.2 Product B: desktop notification terminal and LLM
Description: The device stands at the computer and shows important information without opening another window on the monitor.
Functions:
- pC notifications, - calendar, - tasks, - git/CI/CD status, - server monitoring, - local LLM text replies, - focus/Pomodoro mode, - recording of short voice memos.
For whom:
- programmers, - administrators, - electronics engineers, - content developers, - people working remotely.
Page:
- "always visible" without glowing, - quick glance, - less distraction than a smartphone.
Risk:
- difficult price positioning because competition is a second monitor, phone or tablet. - success depends on highly refined desktop software.
My rating: good niche product, especially for technical users.
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4.3 Product C: room, desk or workstation plaque
Description: Panel mounted at conference room, laboratory workstation, hotel room, doctor's office, production workstation.
Functions:
- room reservations, - "occupied/free" information, - schedule, - QR for bookings, - voice announcements, - temperature/humidity sensor, - local API, - battery or USB-C operation.
Why RLCD:
- readable in the light, - does not shine in the corridor, - looks more "paper-like" than a cheap tablet, - content changes frequently, but does not need to be video.
- fault reading, - parameter configuration, - data logging to TF card, - cSV export, - on-screen service instructions, - voice messages for test procedures.
Why it makes sense in Europe:
- large market for heat pumps, photovoltaics, energy storage and EV chargers, - many installations require simple field diagnostic tools, - a phone is not always comfortable in the sun and when working with gloves.
Risk:
- necessary certifications, - mechanical resistance, - insulation and electrical safety, - support of multiple manufacturer protocols.
My rating: a high value product, but rather for a company with industry experience.
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4.5 Product E: warehouse picking terminal
Description: Device for trolley, rack or employee forearm.
Functions:
- list of items for picking, - voice confirmation, - audio signals, - scanning via attached UART/BLE reader, - integration into WMS, - operation on 18650.
Power:
- RLCD readable in a brightly lit hall, - lower cost than an industrial Android terminal, - audio speeds up work.
Risk:
- drop resistance, - ergonomics requirements, - Wi-Fi roaming, - integration with storage systems required.
My rating: interesting B2B, but the Waveshare board itself is too fragile. Need an industrial version.
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4.6. Product F: senior assistant / reminder
Description: A simple reminder device for medication, drinking water, appointments, contact with family.
Functions:
- large messages, - loud reminders, - button or voice confirmation, - calendar, - no-response alarm, - easy contact with the caregiver.
Pluses:
- screen does not tire eyes, - large letters, - audio, - no need to operate smartphone.
Regulatory notice: If the device is going to be advertised as medical, diagnostic or influencing therapy, it is possible to enter MDR territory. It is much safer to position it as a care organiser/reminder , with no medical claims. Additionally, it is a good idea to design according to accessibility principles, as the European Accessibility Act has been in force since 28 June 2025 and includes common accessibility requirements for selected products and services, especially with older people and people with disabilities in mind. ( consilium.europa.eu )
My assessment: socially very sensible, commercially more difficult by liability and end user support.
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4.7. Product G: energy-efficient information board / eco-dashboard
Description: Panel for schools, offices and public buildings showing:
- energy consumption, - pV production, - temperature, - CO₂ with the addition of a sensor, - air quality, - administrative messages.
Why it fits:
- Europe places a strong premium on energy efficiency, - device can act as 'visible energy education', - RLCD does not generate another glowing screen on the wall.
My rating: good product for BMS integrators and education.
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5. What would need to be changed to make this a product
Hardware
1. Hardware - rLCD protection, - wall and desk mounting, - access to 18650, - space for loudspeaker acoustics.
2. Optional backlighting - not the classic illumination, but a soft frontlight or side diodes, - activated only by a button/motion.
3. User input - minimum: 3-4 buttons, - better: encoder with button, - touch not necessary; with RLCD, buttons are sometimes more reliable.
4. Power supply - cell voltage measurement, - reverse polarity protection, - good charging circuit, - sleep modes, - battery compliance.
EU battery regulations stipulate that from 2027 onwards, portable batteries in devices are to be in principle removable and replaceable by the end user, which just happens to fit well with the 18650 basket concept. ( consilium.europa.eu )
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Firmware
Necessary components in the commercial version:
- secure boot, - flash encryption, - signed OTA, - no default passwords, - wi-Fi provisioning via BLE or SoftAP, - local configuration panel, - offline mode, - export of user data, - data deletion, - diagnostic logs, - MQTT/HTTP/WebSocket, - integration with Home Assistant, - watchdog, - recovery partition, - update policy and vulnerability reporting.
Without this, IoT product in Europe will be increasingly difficult to sell legally and securely.
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6. The best directions in my opinion 6
Best hobby project
Local Home Assistant terminal + LLM + notifications.
Why:
- uses screen, - uses audio, - uses Wi-Fi, - has real usability, - fits well with the electrod.pl community, - it can be developed in stages.
Proposed order of implementation:
1. mQTT dashboard, 2. web-based configuration, 3. audio notifications, 4. wake-word, 5. simple local commands, 6. integration with Home Assistant, 7. optional LLM backend.
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Best B2C commercial product
Private smart-home panel with voice and RLCD screen.
Positioning:
> "Not a tablet. Not a smart speaker with the cloud. A local, quiet home panel with a screen as readable as paper."
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Best B2B commercial product
Information board / station panel / room display.
Positioning:
> "Battery operated, light readable, non-lit information panel with local API and fleet management."
This makes sense, as B2B can more easily justify a price above £100, and the value of the device comes from the integration and software, not the board itself.
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7. Summary
This board fills a very interesting gap between the three classes of devices:
- e-paper: super-efficient but slow, - TFT/OLED: fast, but luminescent and power-hungry, - smart speaker: good audio, but usually without a good local screen.
ESP32-S3 + RLCD 4,2" + audio + microphones gives a platform for local, quiet, private human-system interface . I see the greatest potential in: Home Assistant, B2B panels, service terminals and notifications/LLM. The biggest limitation is not the processor, but software refinement, power management, housing, regulatory compliance and UX quality.
You can call me in any topic by writing @ElektrodaBot. Disclaimer: Some answers provided by the ElektrodaBot may be inaccurate. Elektroda not responsible for accuracy, reliability or completeness of the information presented. All ElektrodaBot responses should be verified by the user. OpenAI can monitor and save information entered after calling ElektrodaBot.
So there you have it, you can act. Throw in some more vibe coding, have it program ready-made modules for you, you can personalise for a particular company the functionality on the board, basically with one stroke of a prompt. A colleague once said he made displays for a clothing sorting factory with buttons. You used to have to write every line by hand, now the prompt and fly and the module is ready.
A device with a monochrome LCD is unlikely to conquer the market, but, for example, for displaying weather forecasts or share prices or cryptocurrencies it could be suitable, although it would be useful to have an additional 'dimension' in the form of the colours of the course - green or red as the course flies by Electrode notifications could also display when there is a reply, some interesting topic, or when someone decides to report a post because it allegedly underperforms
A device with a monochrome LCD is unlikely to conquer the market, but, for example, for displaying weather forecasts or stock or cryptocurrency prices, it could be suitable, although it would be useful to have an additional "dimension" in the form of course colours of green or red as the price goes up
For statuses in well-lit rooms, and these are mostly offices/factories, it would be OK.
Add physical buttons, not to mention voice control, and it makes a mini communication panel for the manual worker at the desk.
And such modulics certified and dedicated, expensive oh expensive.
I don't quite understand the concept of powering this system. Supposedly rechargeable - but a working ESP with WiFi takes its toll. The chip is not small - a bit unportable (e.g. in a pocket). If it is used for HA (controller or display), it still needs to be charged periodically. It is better to connect it permanently. Maybe a battery as a UPS? But in a power outage there is usually a problem with WiFi or internet anyway. Maybe as an alarm clock? A back-up is useful, but the lack of momentary backlighting gets in the way.
They just made a module to fit as many things/features as possible without thinking about what is useful or worrying about things like power consumption.
That's the kind of thing they design for hobbyists to make a 'wow' effect.
However, the concept with the display, speaker, microphone very cool.
