Build Your Own GasTag Bridge

Total cost: approximately $25 in parts

Parts List

Part Price Notes
YD-ESP32-S3 (N8R2 or N16R8) ~$10 2-pack available
USB-C to USB-A OTG adapter ~$5 JSAUX 2-pack
USB-A to USB-B cable ~$5 The one included with your Analyzer works great
USB-C to USB-C cable ~$8 For powering ESP32 from iPhone
3D Printed Case (optional) Free STL File

How to identify the correct ESP32 board: Look for dual USB-C ports.

GasTag Bridge hardware components

Build Steps

1

Install PlatformIO

Install VS Code from code.visualstudio.com, then install the PlatformIO extension from the VS Code marketplace. This provides the toolchain needed to compile and upload the firmware.

2

Flash the Firmware

Clone the GasTag firmware repository. Open the ESP32Firmware folder in VS Code. Connect the ESP32 to your computer via the UART USB-C port (not the OTG port). Click the PlatformIO Upload button or run: pio run -t upload. Once the initial firmware is flashed, the GasTag iOS app can keep the firmware updated via OTA updates.

3

Connect the Hardware

Connect your setup: iPhone → USB-C cable → ESP32 UART port (for power). ESP32 OTG port → USB-C to USB-A adapter → USB-A to USB-B cable → DiveSoft Analyzer USB port.

4

Test the Connection

Install the nRF Connect app on your phone. Scan for BLE devices and verify you see "GasTag Bridge" advertising. Once verified, download the GasTag app from the App Store to use the full interface.

5

Keep firmware updated

From time to time the GasTag bridge firmware may need to be updated. You can do this manually as before or via the iOS app via OTA firmware updates.

Connection Diagram

┌─────────────────┐      USB-B       ┌─────────────────┐       BLE        ┌─────────────────┐
│  DiveSoft       │ ──────────────►  │   ESP32-S3      │  ~~~~~~~~~~~~►   │    iPhone       │
│  Analyzer H2/O2 │    Serial Data   │   GasTag Bridge │   Notifications  │   GasTag App    │
└─────────────────┘                  └─────────────────┘                  └─────────────────┘
                                            ▲
                                            │  USB-C Power
                                            │  (from iPhone)
                                            │
GasTag hardware setup

Troubleshooting

Upload fails

Use the UART USB-C port, not the OTG port

Crashes on boot

Ensure USB CDC On Boot is disabled in Arduino IDE settings

BLE not advertising

Check serial monitor (115200 baud) for error messages

Can't find device on iPhone

Ensure ESP32 is powered and Bluetooth is enabled on iPhone