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I recently joined FTC team 6417 Blu Cru, and they have been incredibly welcoming and supportive from day one. I want to give back in any way I can. In about two months, we'll be flying to the FIRST Tech Challenge World Championship in Houston, Texas — and that flight is valuable prep time. With so much left to plan and coordinate before worlds, the last thing we can afford is to go dark for several hours in the air.
The device uses WiFi Direct (peer-to-peer), which is permitted by the FAA since it creates a local radio link with no cellular or internet connection. One device acts as the Host, and teammates connect as clients. It supports both text messaging and voice calls across the plane without needing Wi-Fi or cell signal. The hardware is built around the ESP32-S3 microcontroller with a 3.5" touchscreen display running an LVGL-based UI with a virtual QWERTY keyboard, an I2S MEMS microphone, and an I2S amplifier with speaker. Every member of Blu Cru will receive their own custom-built device, so no one has to share or use their personal phone.
One ESP32-S3 acts as the Host — it creates a WiFi Direct (P2P) group that other devices discover and join without any router or internet connection. The host handles all message routing between connected clients, acting as a local hub for the network.
The host device manages the connection and routes all traffic. Each teammate runs a client device that joins the group. Once connected, everyone on the plane can send text messages and make voice calls to each other through the host.
The 3.5" capacitive touchscreen runs an LVGL-based UI with a virtual QWERTY keyboard (lv_keyboard widget), a message thread view, and a call interface. Messages are routed through the host in real time with minimal latency.
The INMP441 I2S MEMS microphone captures voice and sends digital audio directly to the ESP32-S3. On the receiving end, the MAX98357A I2S amplifier drives a small 8Ω speaker. No external DAC needed — everything stays in the digital domain for clean audio.
WiFi Direct is permitted by the FAA because it creates a local peer-to-peer radio link with no cellular or internet connection. Everything runs on-device, completely self-contained — fully legal under FAA PED guidelines.
WiFi Direct operates as a peer-to-peer radio link — no internet, no cellular tower, no airline network. The FAA explicitly permits this class of device in flight mode, making this solution legal and practical.
For a robotics team heading to worlds, the flight to Houston is prime prep time. Being able to message and call teammates on the same plane without relying on expensive in-flight WiFi is a real productivity win.
This isn't just for robotics teams. Any group that travels together — engineers, athletes, researchers — could benefit from a self-contained communication device that doesn't need the internet to function.
The full set of technologies powering the Airplane Communicator — from microcontroller firmware to physical hardware.
| Part | Spec | ~Price |
|---|---|---|
| ESP32-S3-DevKitC-1 (N16R8) | 16MB flash, 8MB PSRAM, WiFi + BLE, dual Type-C. Dev board for prototyping — will move to custom PCB around bare ESP32-S3-WROOM-1 module later | $10–15 |
| Part | Spec | ~Price |
|---|---|---|
| 3.5" ILI9488 SPI TFT (480×320) with capacitive touch | Acts as both display and text input via virtual QWERTY keyboard. Driven over SPI, touch over I2C. UI built with LVGL library including lv_keyboard widget | $15 |
| Part | Spec | ~Price |
|---|---|---|
| INMP441 MEMS I2S microphone breakout | Digital I2S output, no ADC noise, solid voice quality | $3–5 |
| MAX98357A I2S mono amplifier breakout | Takes I2S digital audio directly from ESP32-S3, no external DAC needed | $5 |
| 8Ω 1W 28mm speaker | Small cavity speaker, sufficient for close-range cabin listening | $2 |
| Part | Spec | ~Price |
|---|---|---|
| 3.7V 3500mAh LiPo pouch cell | ~10+ hours runtime at ~335mA average draw (WiFi active, display on, intermittent audio). Exceeds 6-hour target for both host and client | $12 |
| TP4056 USB-C charging board (with DW01 protection) | Charge management + over-discharge protection | $2 |
| ME6211 3.3V LDO regulator | Low-dropout, low-quiescent-current. Sits between battery and MCU | $1 |
| Part | Spec | ~Price |
|---|---|---|
| SPDT slide switch | Main power switch | $0.50 |
| JST-PH 2.0mm connector pair | Battery connection | $0.50 |
| Perf board / prototype PCB | Initial wiring before custom PCB | $3 |
| 3D-printed enclosure | ~130mm × 70mm × 20mm form factor, PLA or PETG | Filament cost |
| Subsystem | Draw |
|---|---|
| ESP32-S3 (WiFi P2P active) | ~240mA avg |
| ILI9488 display + backlight | ~80mA |
| Audio (call active, ~30% duty) | ~30mA avg |
| Touch controller (I2C polling) | ~5mA |
| Total average | ~355mA |
Project still in progress — check back after Houston!
Component sourcing and breadboard wiring. Get ESP32-S3 dev board communicating with display, mic, and speaker individually. Bring up WiFi Direct (P2P) between two ESP32-S3 boards.
Build messaging protocol over WiFi Direct (host/client architecture). Implement LVGL-based UI with soft keyboard, message thread view, and call interface. Integrate I2S audio streaming for voice calls.
Combine all subsystems on perf board. Test multi-device mesh in real-world conditions. Optimize power consumption and validate 6+ hour battery life.
Design custom PCB in KiCad around bare ESP32-S3-WROOM-1 module. Integrate charging circuit and LDO on-board. Design and 3D-print final enclosure.
Early prototype — host device
Hardware components laid out
Software UI in development
WiFi Direct connection demo
Live chat and call between devices
