Flash an ESP32-C6 to bridge your Interspace Industries CDEther countdown display to KUMA Timer over Wi-Fi — no more Ethernet cable. Plug in, click Install, configure via browser, done.
Specialist hardware. This page is for users with an existing CDEther display system (Interspace Industries / Plura). It requires soldering three wires to the CDEther PCB. If you're looking for a standalone wireless display, see TC001 or S3-BOX instead.
What you need ~10 minutes
An ESP32-C6 DevKit (any standard dev board — Espressif ESP32-C6-DevKitC-1 or similar).
A USB-C cable.
Chrome or Edge browser required — Safari/Firefox don't support Web Serial.
KUMA Timer on the same Wi-Fi (LOCAL mode) or a cloud relay URL (CLOUD mode).
Hardware wiring (solder once, then it's wireless forever):
The ESP32-C6 uses GPIO4 as UART TX at 3.3 V logic, 9600 8N1. The CDEther RX pad (marked P2 / RX1 on the board) may be 3.3 V or 5 V tolerant — check your board revision. A simple 10 kΩ / 20 kΩ voltage divider is sufficient if 5 V level-shifting is needed. Also connect GND to CDEther GND (P3).
Pad locations on CDEther Rev4:TX1 (CP5) = display TX (you don't need this), RX1 (P2) = display RX (inject here), P3 = GND.
Install firmware
Plug the ESP32-C6 in via USB, then click Install KUMA CDEther Bridge below. If the browser can't find the device, try holding BOOT while clicking — the ESP32-C6 needs to be in download mode.
Plug the ESP32-C6 into your computer via USB.
Click Install KUMA CDEther Bridge below.
In the browser dialog, pick the port (usually CP210x or USB JTAG) and click Connect.
If it fails: hold BOOT, press RST/EN briefly, release BOOT — then retry.
Wait ~60 seconds. Don't unplug.
Done — the onboard LED flashes blue on first boot (Wi-Fi connecting).
Your browser doesn't support Web Serial. Open this page in Chrome or Edge on a desktop computer.
This page must be loaded over HTTPS. Open https://kuma.pl-tech.co.uk/cdether-flasher directly.
What gets flashed: KUMA CDEther Bridge firmware v2.0.0. The merged binary includes bootloader, partition table, and application. Any earlier firmware is fully overwritten.
After flashing — Wi-Fi setup
The ESP32-C6 LED glows blue and broadcasts a hotspot named KUMA-CDEther-XXXX (last 4 = board ID).
From your phone or laptop, connect to that Wi-Fi network. Password: kumasetup.
Open a browser and go to http://192.168.4.1.
Fill in your Wi-Fi SSID and password, choose DHCP or static IP, set the admin password.
Optionally paste a Cloud URL (relay poll URL from the flashers page) for cloud fallback.
Click Save & Reboot. The device connects to your Wi-Fi. LED goes green (local mode active).
Admin password is required to access the config portal once the device is on your Wi-Fi. Default after first flash is empty — set one on the System page.
Operating modes
● LOCAL
Receives KUMA UDP broadcast on port 36700 from the KUMA Timer host. Zero configuration — just be on the same Wi-Fi. Latency <50 ms.
● CLOUD
Polls the KUMA relay every 2 s when LOCAL signal is absent for the configured timeout (default 8 s). Works across different networks. Latency ~1–2 s.
The bridge automatically switches LOCAL→CLOUD after the timeout, and checks back every 15 s — if KUMA reappears on LAN it switches back instantly.
LED status
Solid on — setup hotspot active, or booting
Slow blink — connecting to Wi-Fi
Single short blink — LOCAL packet received from KUMA
Double blink — CLOUD poll OK, data sent to display
Off between blinks — normal idle in LOCAL or CLOUD mode
(XIAO ESP32-C6 has a single orange LED — blink patterns replace colour coding.)
Config portal pages
Browse to the device IP (shown on the Status page at http://<device-ip>/). All pages require the admin password.
Status — current mode, IP address, last packet received, uptime.
Network — change Wi-Fi SSID/password, switch between DHCP and static IP.
System — change admin password, reboot, factory reset (clears all config).
Reset Wi-Fi / factory reset
Lost access to the device? Use the System → Factory Reset button in the portal.
If you can't reach the portal: power off the device, hold BOOT while powering on, then release. The device re-enters setup hotspot mode without losing config. A full factory reset (wipes all settings) can be triggered from the System page.
Troubleshooting
Install button is greyed out. Use Chrome or Edge on desktop — Safari/Firefox don't expose Web Serial.
Browser can't find the device. Try a different USB cable (charge-only cables have no data pins). If still nothing: hold BOOT, press RST briefly, release BOOT — device should appear as USB JTAG/serial debug unit.
LED stays red after connecting. Check Wi-Fi credentials and that the router doesn't use client isolation (AP isolation). KUMA Timer needs to be running and have the CDEther / LOCAL UDP enabled in Settings → Connections.
LED amber but no output to display. Verify cloud URL is correct (use the URL generator on flashers page). Check that the relay is reachable: curl https://relay.kuma.pl-tech.co.uk/health.
CDEther display shows nothing. Verify GPIO4 → CDEther RX1 (P2) wiring and GND connection. Check that baud rate matches the USR module config (9600 8N1). The USR module and ESP32-C6 should not both be connected to CDEther RX simultaneously — use a SPDT switch or disconnect the USR TX line.