The TX16S MKII ships with EdgeTX, but most pilots use maybe 15% of what it can do. Custom voice callouts, global functions that react to telemetry in real time, Lua scripts that visualize GPS coordinates on the color screen — these aren’t gimmicks. They’re the difference between glancing at your radio to see battery percentage and having the radio tell you “battery low, land now” while your eyes stay locked on the quad. This guide covers the advanced features you’ll actually use, not the menu items you’ll scroll past once.
Custom Sounds: Make Your Radio Speak
EdgeTX supports custom WAV files for every system event and telemetry trigger. Out of the box, the “Amber” sound pack is the community standard, but you can add your own callouts.
Sound File Requirements
- Format: 16-bit PCM WAV, mono
- Sample rates: 8 kHz, 16 kHz, or 32 kHz (16 kHz is the sweet spot — clear enough for speech, small enough to load fast)
- File naming: 6 characters max + “.wav” extension (8.3 format)
- Location:
/SOUNDS/en/on the SD card (substituteenfor your language folder)
Creating Custom Callouts
Use any text-to-speech tool to generate WAV files, then convert with ffmpeg:
ffmpeg -i input.mp3 -ac 1 -ar 16000 -sample_fmt s16 output.wav
Copy to the SD card’s /SOUNDS/en/ folder. Restart the radio or run “SD Card → Reload” to see new files.
Wiring Sound Events to Telemetry
Navigate to Special Functions (MDL → Special Functions). Each function has a trigger and an action:
Essential FPV voice callouts:
| SF# | Trigger | Action | Parameter | Repeat |
|---|---|---|---|---|
| SF1 | THs (throttle start) | Play Track | timerst.wav | 1x |
| SF2 | Timer1 > 3:00 | Play Track | thrmin.wav | 30s |
| SF3 | RSSI < 50 | Play Track | rssilow.wav | 15s |
| SF4 | RSSI < 35 | Play Track | rssicrt.wav | 10s |
| SF5 | RxBt < 3.6V | Play Track | rxlow.wav | 20s |
| SF6 | TxBat < 6.8V | Play Track | txlow.wav | 60s |
| SF7 | SA↑ (switch position) | Play Track | armed.wav | 1x |
| SF8 | SA↓ (disarmed) | Play Track | disrmd.wav | 1x |
The repeat interval matters. A 15-second repeat on RSSI warnings means you hear the warning, have time to assess, and hear it again if the condition persists. 5-second repeats create audio clutter that makes you miss critical calls.
Global Functions: Radio-Wide Logic Across All Models
Global Functions execute regardless of which model is loaded. They’re perfect for:
- Radio battery warnings:
TxBat < 6.8V → Play Track "txlow"— works on every model, no per-model configuration needed - Backlight timeout:
No activity 30s → Backlight Off— saves battery on thirsty color screens - Volume control: A pot or slider mapped to volume — adjust audio level without diving into menus
- Screen brightness:
S2 (potentiometer) → Adjust Backlight— dim for indoor, bright for outdoor
Access in Radio Setup → Global Functions. These persist across model changes and firmware updates.
Emergency Kill Switch (Global)
Set up a global override switch that kills the throttle on any model:
- Global Functions → new function
- Switch: SH (momentary, pull to activate)
- Action: Override CH3 (Throttle)
- Value: -100
If a quad goes rogue — stuck throttle, GPS rescue fails, flyaway — pull SH and throttle drops to zero. This overrides the per-model mixer, so it works even if your model’s throttle channel is configured differently.
Lua Telemetry Scripts
The TX16S color screen runs Lua scripts that read telemetry data and render visuals. EdgeTX ships with several, and the community maintains dozens more.
Installing Lua Scripts
Copy .lua files to /SCRIPTS/TOOLS/ on the SD card. Access via SYS → Tools. Some scripts need companion files in /SCRIPTS/<scriptname>/.
Essential FPV Lua Scripts
Betaflight GPS Widget: If your quad has GPS, this script plots lat/lon on the screen, displays satellite count, HDOP, altitude, ground speed, and distance from home. Install from the EdgeTX SD card content pack.
ELRS LUA (ExpressLRS configurator): Built into EdgeTX — no installation needed. Access from SYS → Tools → ExpressLRS. Configure packet rate, power, telemetry ratio, and bind phrase from the radio screen without a computer. This is how you change ELRS settings at the field.
Yaapu Telemetry (for ArduPilot/iNav users): Full HUD display with artificial horizon, compass rose, and flight mode indicator. Overkill for Betaflight quads, essential for fixed-wing FPV with flight controllers running ArduPilot.
Telemetry Screen Widget Configuration
The color screen supports 2 layouts (user-switchable). Set up one screen for freestyle (big RSSI, timer, battery) and another for long-range (GPS coordinates, distance, altitude, heading).
Go to SYS → Screen 1 → Setup Widgets:
– Top bar: RSSI bar, TxBat, Timer
– Main area: Large RxBat gauge (center), GPS lat/lon (if equipped)
– Bottom bar: Flight mode text, VTX channel
Screen 2 (long-range):
– Full-screen GPS widget showing map position, altitude, ground speed, and distance from home
Logical Switches for FPV (Beyond Basic Arm)
Switch confirmation (prevent accidental mode changes):
L01: Edge | SA↑ | 0.0 (instant)
L02: Edge | SA↑ | 0.5 (0.5 second delay)
L03: AND | L01 | L02 | 0.5 (duration)
Use L03 instead of raw SA↑ for critical functions. The switch must be held in position for 0.5 seconds before the function activates — prevents brushed-switch accidents.
Timer-based low battery escalation:
L10: a<x | RxBt | 3.5V (trigger at 3.5V)
SF10: L10 | Play Track | "landnow" | 10s repeat
L11: a<x | RxBt | 3.3V (trigger at 3.3V)
SF11: L11 | Play Track | "battcrit" | 5s repeat
As voltage drops, warnings escalate from informational to urgent.
EdgeTX Hardware Comparison for FPV
| Radio | Screen | Audio Quality | Lua Script Performance | Hall Gimbals | External Module Bay | Best For |
|---|---|---|---|---|---|---|
| TX16S MKII | 4.3″ color 480×272 | Good (built-in speaker) | Excellent (fast CPU) | CNC Hall V4.0 | Full-size JR bay | Telemetry-heavy builds, color screen |
| Boxer | 128×64 B&W | Adequate (small speaker) | Good | Hall V4.0 | Lite bay (Nano) | Daily FPV workhorse |
| Zorro | 128×64 B&W | Adequate | Good | Hall mini | Lite bay (Nano) | Thumb pilots, gamepad grip |
| T-Pro V2 | 128×64 B&W | Weak | Limited (slow CPU) | Hall mini | Internal only | Ultra-portable, whoops only |
What Most Pilots Get Wrong
Mistake 1: Cranking voice volume to 100% and wondering why it clips. The TX16S speaker distorts above 80% volume. Set it at 70-75% and let the amplifier do its job cleanly. If you can’t hear callouts at the field, use an earbud in the 3.5mm jack — it’s cleaner and doesn’t annoy everyone around you.
Mistake 2: Setting aggressive repeat intervals on telemetry warnings. A “low RSSI” callout firing every 3 seconds teaches your brain to filter it out. Set meaningful thresholds (RSSI<50 for awareness, RSSI<35 for action) with 15-20 second repeats. You need to hear the warning and react — not wade through audio spam.
Mistake 3: Loading 400 custom sounds and wondering why the SD card is slow. EdgeTX scans the sounds folder at startup. 400 files in /SOUNDS/en/ adds 2-3 seconds to boot time. Keep only the sounds you actually use. Delete the helicopter and fixed-wing callouts if you only fly quads.
Mistake 4: Overwriting the stock “Amber” sound pack without a backup. The Amber pack has hundreds of perfectly recorded callouts. Don’t replace it — add your custom sounds alongside it. If a stock sound breaks, download the pack from the EdgeTX GitHub releases page.
Mistake 5: Using Lua scripts that poll sensors at 10 Hz and drain CPU. Some third-party Lua scripts hammer the telemetry bus with rapid sensor reads. If your radio screen lags or audio stutters when a Lua script is active, the script is chewing too much CPU. Disable it and find a lighter alternative — the built-in telemetry widgets are well-optimized.
⚠️ Regulatory Notice: The telemetry and Lua scripting capabilities described in this article are configuration-level features of EdgeTX open-source transmitter firmware. Always ensure your transmitter’s RF output (ExpressLRS, Crossfire, or other module) operates within the regulatory domain settings for your region. As of 2026, be aware that some Lua telemetry scripts may access GPS position data — if your FPV drone transmits GPS coordinates over the air, ensure compliance with local data transmission regulations.
For radio gimbal tuning and maintenance, see our radio gimbal calibration guide. For ExpressLRS module configuration via Lua script, the ELRS dynamic power guide covers the on-screen settings you’ll access from the Tools menu.
The RadioMaster TX16S MKII ELRS edition includes everything in this guide out of the box — color screen, CNC gimbals, internal 1W ELRS module, and a 32GB SD card pre-loaded with EdgeTX and sound packs. Available in the uavmodel radio collection.