ElectroIoT/DotGlow-ESP322DotGlow: WiFi + Bluetooth LED matrix clock firmware for ESP32 / ESP32-S3 + MAX7219, with Android app setup
Dotglow v1 is an open-source printed circuit board by ElectroIoT, from the ElectroIoT/DotGlow-ESP32 repository on GitHub, published under the MIT licence. It is a 2-layer board of 128 × 33 mm with 41 parts on 57 nets, routed with 270 tracks and 195 vias.
It is built around the 74AHCT125D, ESP32-S3-WROOM-1-N16R8 and DHT22, with the USBLC6-2SC6 and XC6220B331MR-G among its other parts. Its parts include 10 resistors, 8 capacitors, 7 connectors, 5 ICs and 3 switches. It belongs with the radio and wireless and lEDs and displays boards and the ESP32 boards of this library.
A WiFi + Bluetooth LED matrix clock for ESP32 and ESP32-S3, with its own Android app.
Set it up from your phone in two minutes: no computer, no app accounts, no cloud.
▶ Watch the 30-second demo: YouTube Short
The DotGlow Android app is live on Google Play:
No account, no ads, no tracking. Details and setup guide: mtpcode.com/apps/dotglow.html · feedback: admin@mtpcode.com
Repository map · Features · How it works · Parts · Wiring · Install the firmware · First setup · Using the clock · Stopwatch · Updates · Troubleshooting · For developers · Roadmap · Credits
| Folder | What is in it |
|---|---|
src/ | the firmware (C++, PlatformIO): display, clock, WiFi, web dashboard, Bluetooth |
platformio.ini | build settings for ESP32, ESP32-S3 and test builds |
desktop-flasher/ | a small Windows tool to flash a board over USB |
tools/ · release/ | scripts that build the release images and the firmware list the app reads |
hardware/pcb/ | the custom DotGlow V1 circuit board (schematic, Gerbers, BOM, 3D renders) |
hardware/enclosure/ | 3D-printable cases (STL + OpenSCAD) |
docs/ | architecture, Bluetooth protocol, development and release guides, pictures |
Related repo: the Android app, DotGlow-Android.
| 📱 Android app over Bluetooth | Every setting, WiFi setup, firmware updates, live previews (DotGlow-Android) |
| 🔒 Secure pairing | 6-digit PIN shown on the LED display, encrypted Bluetooth (LE Secure Connections) |
| 🌐 Web dashboard too | Settings page on the clock's IP address, with a login |
| 🕒 Internet time | NTP with time zones and daylight saving, 12 / 24 hour, leading zero, blinking colon, seconds bar, date |
| ✨ Animations | 6 digit-change styles, 5 effects (hourly and at power-on), scrolling messages, special days (birthdays...) |
| 🌙 Brightness | Manual, night mode with its own brightness (or display off), optional light sensor (LDR) |
| ⏱️ Stopwatch | From the app or with an optional push button |
| 🔄 Rotate 180° | Mounted upside down? One tap in the app, or double-press BOOT |
| 🧱 4 to 16 modules | 8x32 up to 8x128, any module type (FC-16, generic, Parola, IC-Station), mirror / flip |
| ⬆️ Updates | From GitHub over WiFi, from the app over Bluetooth, or a new board straight from the phone over USB |
| 🛟 Safe mode | After repeated crashes it starts with only WiFi + updates, so a bad update can always be fixed |
| Roll down | Roll up | Dissolve |
|---|---|---|
 |  |  |
| Slide | Flip | Drop & bounce |
 |  |  |
| Sparkle | Wipe | Rain |
|---|---|---|
 |  |  |
| Boxes | Pac-Man | Stopwatch |
 |  |  |
All pictures are generated from the firmware's own fonts and frame logic (tools/make_images.py), so they match the real display.
| Part | Notes |
|---|---|
| ESP32-S3 DevKitC-1 or ESP32 DevKit (WROOM-32) | Any flash size from 4 MB. ESP32-S2 has no Bluetooth: not supported |
| MAX7219 4-in-1 LED matrix (8x32) | The common blue "FC-16" boards. Chain more for 8x64 ... 8x128 |
| 5 jumper wires | Female-female for most boards |
| 5 V / 1 A (or stronger) phone charger + cable | Required. A computer USB port is too weak for the display, see power |
| 470-1000 µF capacitor | Across VCC / GND at the display (+ leg to VCC). Strongly recommended |
| Optional: LDR + 10 kΩ resistor | Automatic brightness |
| Optional: push button | Stopwatch without the phone |
| Optional: 3D-printed case | hardware/enclosure: leaning desk case, smoked acrylic front, DC jack; STLs for ESP32-S3, ESP32 DevKit, NodeMCU, D1 mini |
Using an ESP8266 / NodeMCU instead? That is the ESP8266 Matrix Clock (WiFi + web page, no Bluetooth). The DotGlow app can install it too.
| ESP32-S3 DevKitC-1 | ESP32 DevKit |
|---|---|
 |  |
| MAX7219 | ESP32-S3 | ESP32 DevKit |
|---|---|---|
| VCC | 5V | VIN (5V) |
| GND | GND | GND |
| DIN | GPIO11 | GPIO23 |
| CS | GPIO10 | GPIO5 |
| CLK | GPIO12 | GPIO18 |
| LDR (optional) | GPIO1 | GPIO34 |
| Stopwatch button (optional) | GPIO4 | GPIO13 |
Light sensor: LDR from 3V3 to the LDR pin, 10 kΩ from that pin to GND, then turn on Auto brightness.
⚠️ ESP32 DevKit: never use the pins labelled CLK, SD0, SD1, SD2, SD3, CMD. They are the board's flash memory pins; a wire there stops the board from starting (
invalid header: 0xffffffff). The display's CLK goes to D18, not to the pin called "CLK". Always wire the display's IN end (pins marked DIN), not DOUT.
Power the clock from a 5 V / 1 A (or stronger) phone charger. A computer's USB port cannot drive the display: the LEDs stay dim, all LEDs stay on or show garbage, the board keeps restarting and drops off USB. That was the cause of every "display does not work" case during testing; a 1 A charger fixed all of them. Flashing from a computer is fine; test the display on the charger.
Connect OUT of one board to IN of the next, then set the module count in the app (Display).
| Modules | Display | Supply |
|---|---|---|
| 4 | 8x32 | 5 V / 1 A (USB is fine) |
| 8 | 8x64 | 5 V / 2 A, separate supply |
| 12 | 8x96 | 5 V / 3 A |
| 16 | 8x128 | 5 V / 4 A |
Above 4 modules feed 5 V to the boards directly (not through the ESP32), with a 470-1000 µF capacitor at each board.
Open mtpcode.com/flash in Chrome or Edge on a computer, plug the board in, press Install. ESP32, ESP32-S3 and ESP8266 (NodeMCU / D1 mini).
desktop-flasher: a small program that finds the board, downloads the latest firmware and installs it
(window or command line, Windows / Linux / macOS). python desktop-flasher/dotglow_flasher.py or the .exe.
pio run -e esp32s3 -t upload --upload-port COM5 # ESP32-S3 (the "USB" port)
pio run -e esp32dev -t upload # classic ESP32esptool.py write_flash 0x0 dotglow-esp32s3-full.binFull images (bootloader + partitions + app) are made by python tools/release.py.
No app? The clock opens a WiFi hotspot DotGlow-XXXX; join it and the setup page opens (or http://192.168.4.1).
http://<clock IP> or http://dotglow.local, with an optional login password.On the display
| Running | Paused (blinks) | After an hour |
|---|---|---|
|  |  |
MM:SS, tenths fill the bottom row | Digits blink, time kept | HH:MM, the bottom row fills once a minute |
Button wiring (optional)
HH:MM:SS all the time.| How | When to use |
|---|---|
| GitHub over WiFi | Automatic at night (if enabled) or Updates → Check now |
| App over Bluetooth | Updates → Update over Bluetooth: no WiFi needed, about 30 s |
| USB from the phone | New or broken boards: Install firmware |
| Web upload | Upload firmware.bin on the web page (password protected) |
A custom 128 x 31.1 mm PCB that stacks on the back of the 4-in-1 MAX7219 module: ESP32-S3, USB-C, I2S speaker amplifier,
stopwatch / LDR / DHT22 connectors, and an I2C port for a clock chip. Schematic, Gerbers, BOM, 3D renders and the
KiCad / EasyEDA files are in hardware/pcb/. Untested V1. ▶ Watch the PCB Short.
| Problem | Fix |
|---|---|
| Board light is on but the app doesn't see the clock | Join the grounds: display GND, board GND and the power supply GND must be connected together. Use a stable 5 V supply: a weak one restarts the board when Bluetooth starts |
| Dim, all LEDs stuck on, or garbage | Power: use a 5 V / 1 A charger, not a computer USB port; add the capacitor |
| Only the first module works | A broken link between modules (re-solder the joints between module 1 and 2) |
| ESP32 doesn't start after wiring | A wire is on CMD / SD0-SD3 / CLK (flash pins): move it |
| Text scrambled / mirrored | App → Display → module type / mirror / flip |
| Upside down | App → Display → Rotate 180°, the rotate button on the dashboard, or double-press BOOT |
| Keeps restarting | Better 5 V supply, add the capacitor; after 3 crashes it starts in safe mode |
| Can't pair | Use the PIN on the display (not 0000 / 1234). After a factory reset the app re-pairs by itself |
| "Getting time..." forever | WiFi has no internet, or the time zone is wrong (App → Clock & time) |
| Board drops off USB / flash stops half way | Take the display's 5 V wire off the board while flashing (the display draws more than USB gives); short thick data cable, another port |
| USB install fails | Use a data cable; hold BOOT, tap RESET, release BOOT, try again |
| Doc | What's in it |
|---|---|
| docs/ARCHITECTURE.md | Modules, main loop, settings storage, safe mode, OTA |
| docs/PROTOCOL.md | Bluetooth GATT service, request / response format, every operation |
| docs/DEVELOPMENT.md | Build envs, test build, serial gotchas, testing with the app |
| docs/RELEASE.md | Version bump, release images, publishing the firmware catalog |
| CHANGELOG.md | What changed in each version |
| CLAUDE.md | Quick brief for AI coding assistants |
| Phase | What | Status |
|---|---|---|
| 1 | ESP32 / ESP32-S3 port of the ESP8266 Matrix Clock | ✅ working on an ESP32-S3 with the real MAX7219 display |
| 2 | Bluetooth service + protocol | ✅ tested on a Motorola Edge 40 Neo (Android 15) |
| 3 | Android app: pairing, dashboard | ✅ |
| 4 | Android app: all settings, WiFi setup, app PIN lock, setup guide | ✅ |
| 5 | Firmware updates over Bluetooth | ✅ 1.2 MB in 26 s |
| 6 | Flash a new board from the phone over USB-OTG (ESP32, ESP32-S3, ESP8266) | ✅ tested on an ESP32-S3 |
| 6b | Stopwatch with an optional button | ✅ |
| 6c | 3D-printed case (OpenSCAD, parametric) | 🟡 designed, test print pending |
| 6d | Temperature + humidity from a DHT22 (shown on the display and in the app); the case has a pocket for it | ⬜ planned |
| 7 | Public release | ✅ app live on Google Play, firmware repo public |
MIT, see LICENSE. Made with care in India by Manoranjan · ElectroIoT.
The code is MIT licensed, but the DotGlow name, logo and app icon are not covered by the licence.
Forks and rebuilt apps are welcome; please publish them under your own name, icon and package
(not com.electroiot.dotglow), so users can tell them apart from the official app.
| Qty | Value | Footprint | References |
|---|---|---|---|
| 4 | 100nF | Capacitor_SMD:C_0805_2012Metric | C3, C6, C7, C8 |
| 4 | 10k | Resistor_SMD:R_0805_2012Metric | R1, R4, R5, R8 |
| 4 | M3 | MountingHole:MountingHole_3.2mm_M3 | H1, H2, H3, H4 |
| 2 | 22uF 10V | Capacitor_SMD:C_1206_3216Metric | C1, C2 |
| 2 | 4.7k | Resistor_SMD:R_0805_2012Metric | R6, R7 |
| 2 | 5.1k | Resistor_SMD:R_0805_2012Metric | R9, R10 |
| 1 | 100k | Resistor_SMD:R_0805_2012Metric | R3 |
| 1 | 10uF 10V | Capacitor_SMD:C_0805_2012Metric | C5 |
| 1 | 1k | Resistor_SMD:R_0805_2012Metric | R11 |
| 1 | 1uF | Capacitor_SMD:C_0805_2012Metric | C4 |
| 1 | 74AHCT125 | Package_SO:SOIC-14_3.9x8.7mm_P1.27mm | U3 |
| 1 | BOOT | Button_Switch_SMD:SW_SPST_B3S-1000 | SW2 |
| 1 | DHT22 | Connector_JST:JST_XA_B03B-XASK-1_1x03_P2.50mm_Vertical | J3 |
| 1 | DISPLAY IN | Connector_PinHeader_2.54mm:PinHeader_1x05_P2.54mm_Vertical | J2 |
| 1 | ESP32-S3-WROOM-1-N16R8 | RF_Module:ESP32-S3-WROOM-1 | U1 |
| 1 | I2C (RTC V2) | Connector_JST:JST_XA_B04B-XASK-1-A_1x04_P2.50mm_Vertical | J4 |
| 1 | LDR | Connector_JST:JST_XA_B02B-XASK-1-A_1x02_P2.50mm_Vertical | J6 |
| 1 | MAX98357A | Package_DFN_QFN:TQFN-16-1EP_3x3mm_P0.5mm_EP1.6x1.6mm | U4 |
| 1 | NTC 10k | Resistor_SMD:R_0603_1608Metric | RT1 |
| 1 | Power LED | LED_SMD:LED_0805_2012Metric | D1 |
| 1 | RESET | Button_Switch_SMD:SW_SPST_B3S-1000 | SW1 |
| 1 | SPEAKER 8R 2W | Connector_JST:JST_XA_B02B-XASK-1-A_1x02_P2.50mm_Vertical | J5 |
| 1 | SPK+ pad | TestPoint:TestPoint_Pad_D2.5mm | TP1 |
| 1 | SPK- pad | TestPoint:TestPoint_Pad_D2.5mm | TP2 |
| 1 | STOPWATCH | Button_Switch_SMD:SW_SPST_B3S-1000 | SW3 |
| 1 | STOPWATCH SW | Connector_JST:JST_XA_B02B-XASK-1-A_1x02_P2.50mm_Vertical | J7 |
| 1 | USB-C 5V | Connector_USB:USB_C_Receptacle_GCT_USB4105-xx-A_16P_TopMnt_Horizontal | J1 |
| 1 | USBLC6-2SC6 | Package_TO_SOT_SMD:SOT-23-6 | U5 |
| 1 | XC6220B331MR-G | Package_TO_SOT_SMD:SOT-23-5 | U2 |
It measures 128 × 33 mm and has 2 copper layers, 1.6 mm thick.
41 parts, built around the 74AHCT125D, ESP32-S3-WROOM-1-N16R8, DHT22 and USBLC6-2SC6. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
From the ElectroIoT/DotGlow-ESP32 repository on GitHub, at the commit this page was made from: the board is hardware/pcb/kicad/dotglow-v1.kicad_pcb and its schematic hardware/pcb/kicad/dotglow-v1.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Its repository publishes it under the MIT licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).
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