NMEATouch20

NMEATouch20 receives NMEA 0183 and AIS data over UDP from your boat network — for example from the NMEA WiFi Bridge project — and presents it on a clear touchscreen display. If your boat has an NMEA 2000 network, this unit is fully compatible. Third-party NMEA 2000 WiFi gateways read the CAN bus and transmit standard NMEA 0183 sentences onto the boat WiFi — the same format NMEATouch20 reads. No special configuration is needed (not yet confirmed by the author — reports welcome).

The centrepiece of the AIS screen is the passing ahead / passing behind display. For each AIS target on a converging course, the unit shows how far ahead of the other vessel’s bow, or behind her stern, you will pass.

This matters because CPA — closest point of approach — is measured between AIS antennas, not between the hulls. Ship antennas are typically mounted at the stern, so on a 400-metre vessel the antenna can be nearly a quarter of a mile behind the bow. A CPA of 0.3 miles past the antenna could still mean passing very close to the bow. By knowing how far ahead of the bow you will pass, and whether speeding up or slowing down increases that margin, you get a clear and actionable picture of your actual clearance. The unit accounts for the length of the vessel ahead of her antenna when making this calculation.

This is particularly useful when crossing a busy shipping lane at right angles: you can see immediately whether you will clear the projected track with a comfortable margin, and which adjustment — a little more speed or a little less — gives you the most room.

The AIS target table also shows range, bearing, CPA, and TCPA for all visible vessels. Speed and course screens give large, easy-to-read readouts from your instruments. NMEATouch20 connects to the same UDP/TCP NMEA stream as your chart apps, so Navionics, iNavX, and similar apps continue to work alongside it.

The project uses the Guition ESP32-S3 4848S040 — an all-in-one module combining an ESP32-S3 microcontroller, 480×480 LCD, GT911 capacitive touch controller, and optional SD card slot on a single compact board. Buy the unit on the open market — it is widely available online for around £20–£25.

No additional components, wiring, or soldering are required. Flash the firmware using the button below, run through the browser setup, and it is ready to use.

The unit is not waterproof. Mount it inside the cabin or in a sheltered position where it will not be exposed to rain or spray. The display is best viewed in shade or in a dimly lit interior; direct sunlight will wash it out.

After flashing, the unit starts in access point mode with its own WiFi hotspot. Connect to it using the default credentials below, then open a browser and navigate to 192.168.4.1 to reach the configuration page.

You will need to enter at minimum:

• Your vessel's MMSI number — required to exclude your own vessel from the AIS target list
• Your boat WiFi SSID and password if you want the unit to join your existing network rather than run as a standalone hotspot

Save the settings and the unit will restart. If you entered your boat WiFi credentials it will connect to that network; otherwise it continues as a hotspot. Either way it is now ready to receive NMEA and AIS data.

To reset all settings back to factory defaults, reflash the unit using the button above. The Guition module has no physical reset button — reflashing restores the firmware and clears the saved configuration, returning the unit to AP mode with the default credentials above.