Build guide
LilyGo, ADS1115, O2-cell wiring, assembly, and first test.
Open build guide
DIY firmware and case for divers
Nitrox Analyser
Build your own compact ESP32-S3 oxygen analyser, reuse a galvanic O2 cell you already trust, and print cylinder labels over Bluetooth. No coding experience is required: the firmware installs directly from this website in desktop Chrome or Edge.
Available now
Install first. Add the licence when your build is ready.
The public firmware installer is open. Flash it to a supported LilyGo T-Display S3, finish the build, and use the local Web UI to find the 12-character Device ID. Email that ID when you are ready to purchase the licence for your board.
- No Arduino IDE, source build, or online checkout is required.
- The €25 one-off licence unlocks the analyser O2 display and printing features.
- Paste the supplied code into Activate existing key in the device Web UI.
Start your build
Install the firmware now. When you want to unlock it, send the Device ID shown in the Licence section.
Open USB installer Request licence by email Online card payment is not enabled yet.
Real-time O2
Large oxygen percentage display from a galvanic O2 cell.
Use your sensor
Works with common galvanic oxygen cells through an ADS1115 ADC.
Bluetooth labels
Print MOD stickers to supported Niimbot printers.
USB install
Flash from desktop Chrome or Edge with no coding or Arduino IDE required.
Board
LilyGo T-Display S3
Software licence
€25 one-off
Skill level
Basic soldering, no coding
Printer
Niimbot B1/B21
Build yourself
A small analyser built from parts you source yourself.
This is for divers who are comfortable assembling their own kit. Print the housing, assemble the case around a LilyGo T-Display S3, wire the ADS1115, and connect a galvanic O2 sensor cell you already have or can source separately. The software side is ready to flash from this website.
- Fits in the palm of your hand once assembled.
- Case uses the supplied 3MF print file from the product download package.
- No electronics are sold here; you source, solder a few wires, flash, and verify the device.
Measure and calculate
Clear O2 and MOD readings on the device.
The firmware reads the oxygen cell through the ADC, shows the current oxygen percentage, and calculates MOD values for common pO2 settings directly on the colour display.
- Single-point air calibration is stored on the device.
- Battery state and sensor millivolts are visible while analysing.
- The Web UI exposes settings, owners, history, diagnostics, WiFi, and updates.
Bluetooth label printing
Send a finished MOD label straight to a Niimbot printer.
Pair a supported Niimbot B1 or B21 printer and the analyser can print a gas sticker with O2 percentage, MOD, END, date, and owner name. It keeps the bench workflow simple: analyse, confirm, print, stick the label on the cylinder.
- Owner names are stored for repeated label printing.
- Print history is kept in the local Web UI.
- Update-only flashing keeps printer, WiFi, owner, history, and license settings.
Device Web UI
Configure, calibrate, pair printers, and update from the browser.
The local Web UI uses the same blue theme as this site and gives you access to live O2 readings, calibration, MOD settings, owner names, print history, WiFi, OTA updates, diagnostics, and licensing.
- Works from a phone, tablet, or laptop on the same network.
- Settings stay on the device and survive update-only flashing.
- The Web UI is part of the firmware; no app store install is needed.
Shopping list
Parts for the Nitrox Analyser
We provide firmware, documentation, and the supplied case file. You source the electronics, reuse or buy a suitable oxygen sensor cell, solder the analyser, flash it over USB from the website, and verify it against known gases before diving. You do not need to compile code or install developer tools.
| Qty | Part | Purpose |
|---|---|---|
| 1 | LilyGo T-Display S3 | ESP32-S3 board with TFT display, USB-C, battery charging, and PMU. Buy the bare board without fitted pin headers and without a housing so it fits the printed enclosure. |
| 1 | ADS1115 module | 16-bit ADC for reading the low-voltage oxygen cell signal. |
| 1 | Galvanic oxygen sensor cell | R-17D, R-22D, or equivalent cell suitable for your analyser design. |
| 1 | 3.7V LiPo battery with a 1.25 mm plug | Use a single-cell battery whose 1.25 mm connector and polarity match the LilyGo battery socket; typically 500–1000 mAh. |
| 1 | Square tactile momentary push button, 6 mm high | Small solderable button for the one-button menu and print control. |
| 1 each | 22k and 10k resistors | USB detection voltage divider. |
| 12 | 6x3mm neodymium magnets | Magnetic closure for the printed housing. |
| 1 | O2-cell connector matched to your cell | Provides a removable, strain-relieved connection from the galvanic cell to ADS1115 A0/A1. |
| As required | M2 machine screws and M2 heat-set inserts | Secure the printed housing; use the quantity and screw length specified by the released housing revision. |
| 1 set | Printed housing parts | Printed body, cover, and the small housing parts supplied with the design. Link coming soon. |
| As needed | Short insulated wire and heat-shrink | Sensor, ADS1115, button, and divider wiring with strain relief. |
| Optional | Niimbot B1/B21 printer | Bluetooth gas label printing. |
Tools
What you need on the bench
Soldering iron, multimeter, heat-shrink, wire cutters, USB-C cable, and a printed case.
Skill level
No coding experience required
Flash via the website, assemble the case, solder a few wires, calibrate, and verify against known gas.
Assembly and soldering
Nitrox Analyser pinout
Keep sensor wiring short, strain-relieved, and away from noisy power leads. The oxygen cell is a tiny millivolt source, so check polarity before soldering and verify the reading in air before closing the case.
| Connection | LilyGo / module pin | What to solder |
|---|---|---|
| O2 cell + | ADS1115 A0 / AIN0 | Positive oxygen cell signal to ADS1115 A0. |
| O2 cell - | ADS1115 A1 / AIN1 | Negative oxygen cell signal to ADS1115 A1. |
| ADS1115 power | 3.3V and GND | Power the ADC from 3.3V only, with common ground to the ESP32. |
| ADS1115 I2C | GPIO17 SCL, GPIO18 SDA | Connect ADS1115 SCL to GPIO17 and SDA to GPIO18. Tie ADS1115 ADDR to GND. |
| Button | GPIO3 and GND | Momentary push button to ground; firmware uses the internal pull-up. |
| USB detect | GPIO13 | USB 5V through 22k to GPIO13, then 10k from GPIO13 to GND. |
| Battery | BAT+ and BAT- | Single-cell 3.7V LiPo connected to the LilyGo battery connector or pads. |
- Never feed 5V into a 3.3V GPIO. The USB-detect input needs the resistor divider.
- Do not put power through the oxygen cell. The cell feeds only the ADS1115 inputs.
- After soldering, power by USB first, check ADS1115 detection, then calibrate in clean air.
Wiring diagram
Connect the oxygen cell through the ADS1115.
Common galvanic oxygen cells such as R-17D, R-22D, or compatible analyser cells are supported when they produce a small millivolt signal. Check cell polarity with a multimeter, expect roughly single-digit to low-teens millivolts in air for many cells, and never power the cell.
Printed housing
Print the case, then build into it.
The case is designed around the LilyGo T-Display S3, ADS1115 module, O2-cell connector, M2 heat-set inserts, and magnetic closure. Link coming soon.
Link coming soon.
Reuse what you have
Made for existing cells, spare parts, and workshop builds.
The intention is not to sell another closed analyser box. It is firmware, a printable housing, and a simple build path for people who already have oxygen sensors, printers, ESP32 boards, or the confidence to source them.
- Print the housing. When the housing link is available, print the parts (or order a printed set), fit the magnets and M2 heat-set inserts, and dry-fit the board and sensor path.
- Wire the electronics. Use the pinout above to connect ADS1115 over I2C, wire the O2 cell to A0/A1, add the button, USB-detect divider, and battery.
- Flash the firmware. Open the USB installer in desktop Chrome or Edge, select Nitrox Analyser, then use full install for a new board. After flashing, unplug and reconnect USB power if the setup WiFi or display does not appear within 30 seconds.
- Configure and calibrate. Start the device, connect to the Web UI if needed, pair a printer, then calibrate in clean air using the firmware's 21.0% O2 reference.
- Verify before use. Compare against known gas or a trusted analyser and verify every label before it goes on a cylinder.
Cost before you install
The hardware is DIY. The analyser software is licensed separately.
We do not sell the electronics, oxygen sensor, battery, printer, or finished analyser. You source and build those yourself. The Nitrox Analyser firmware licence costs about the price of one twinset Nitrox fill, so know this before flashing and activating the analyser. Install first, then email your Device ID to purchase the code for that board.
Licence price
€25
one-off digital licence
End price for German consumers. No VAT shown under §19 UStG; no shipping costs for digital delivery.
Nitrox analyser firmware, Web UI, OTA updates, and Bluetooth label printing.
How do you purchase?
Install the firmware, open the device Web UI, and email the 12-character Device ID to hello@nitroxanalyser.com. I will arrange payment directly and send the matching activation code. Stripe checkout is not enabled yet.
USB flashing
Install from your browser now
The installer supports update-only and full-install modes. Update-only keeps saved settings intact. Full install is for new boards, recovery, unknown firmware, or partition changes. Firmware installation does not require a payment step.
- Use desktop Chrome or Edge.
- Connect the ESP32-S3 by USB.
- If it does not appear, disconnect USB, hold BOOT while reconnecting USB, then release BOOT and retry.
- Select the product and install mode.
- After flashing, unplug and reconnect USB power if setup does not appear.
- Open the device Web UI and email its Device ID when you want to purchase the licence.
Calibrate and verify
Calibrate in clean air using the firmware's 21.0% O2 reference, then compare the finished analyser against a trusted analyser or known gas before relying on it. Repeat calibration and verification whenever you change the cell, wiring, housing, battery setup, or firmware.
Detailed documentation
Build, calibrate, and troubleshoot with the full guides.
These pages are available as searchable HTML and link directly to the diagrams and downloadable parts list.
Online manual
Setup, controls, analysis, Niimbot printing, licence, and updates.
Open HTML manualCalibration guide
Clean-air preparation, pressure and temperature limits, and independent verification.
Open calibration guideTroubleshooting
Sensor, ADC, Wi-Fi, printer, power, activation, and update faults.
Open troubleshootingDownloadable BOM
A spreadsheet-ready CSV with quantities, specifications, and required/optional status.
Download Nitrox BOMBuilt from technical and cave-diving experience
Created for the gas logistics of demanding dives.
Dr. Clemens Chaskel began this project after finding no market solution that met his practical needs for long-duration cave dives, dives deeper than 100 metres, mixed teams, and complex gas logistics.
Field-led engineering
More than 30 years of diving experience, GUE Cave 2, CCR 2+, and Tech 2+ qualifications, and a Chartered Engineer's approach shape the analyser, its labels, and its documentation.
About Dr. Clemens Chaskel
Also available
Trimix Analyser Connector
Many technical and cave divers already love the Divesoft Trimix analyser. This independent ESP32-S3-Zero adapter connects that analyser to a Niimbot printer for seamless analysis label printing, with Nitrox labels included and Trimix labels available through Pro.
Important safety note
This is DIY diving equipment firmware and documentation, not a finished certified commercial analyser. You are responsible for the build, calibration, wiring, and independent verification. Never rely on a single unverified reading before diving.