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EdgeTX model configuration

Summary

EdgeTX is the open-source firmware running on the RadioMaster TX16S MKII transmitter. The libdrone model configuration sets channel order (AETR), maps flight-critical switches (arm, GPS Rescue, profile select, low-speed mode), configures ELRS at 250 Hz LBT for EU regulatory compliance, and enables telemetry for in-transmitter battery and RSSI monitoring. The model must be created manually in EdgeTX — there is no importable binary model file.

Concept

AETR channel order

libdrone uses AETR channel assignment: Aileron on CH1, Elevator on CH2, Throttle on CH3, Rudder on CH4. This matches Betaflight's default CRSF channel expectations and avoids the need for channel remapping in Betaflight. The alternative (TAER, common in DJI workflows) would require reconfiguring the CRSF channel assignments on the FC.

ELRS 250 Hz LBT

ExpressLRS in EU must operate in LBT (Listen Before Talk) mode: the transmitter checks channel occupancy before each transmission. This is a regulatory requirement in several EU countries for the 2.4 GHz band. At 250 Hz, one packet is sent every 4 ms. Total stick-to-FC latency is approximately 6–8 ms — well within the threshold for responsive control.

LBT adds a small variable latency per packet (the listen step before talk) but in practice this is imperceptible and the link statistics show no significant packet loss increase versus non-LBT mode in typical EU operating environments.

Dynamic power

ELRS dynamic power adjusts transmit power automatically based on link quality. At close range (strong signal) it runs at minimum power (10 mW). As range increases or obstacles intervene, it increases to the configured maximum (100 mW for LBT/EU regulatory limit). This reduces RF noise in the 2.4 GHz band during proximity operations without requiring manual power adjustment.

Reference

TX16S switch assignments

Switch Label Function Positions
SF ARM Arm/disarm Up = disarmed, Down = armed
SC RATE Rate profile select 3-pos: Rate1 / Rate2 / Rate3
SD LSPD Low-speed mode Up = Profile 1, Down = Profile 2
SE RESC GPS Rescue manual Momentary (spring-return)
SH BUZZ Lost-drone buzzer Momentary
SA VTX VTX power 3-pos: 25mW / 200mW / 800mW

ELRS module settings

Parameter Value
Frequency 2.4 GHz
Regulatory domain LBT (EU)
Packet rate 250 Hz
Telemetry ratio 1:16
Switch mode Wide
Model Match OFF
Dynamic Power ON
Min Power 10 mW
Max Power 100 mW (LBT limit)

EdgeTX model setup sequence

  1. Create new model: Model Setup → Name: libdrone_V246
  2. Internal RF: ELRS, 250 Hz, LBT regulatory domain
  3. Channel order: AETR
  4. Mixes: standard AETR on CH1–CH4 (no mixing required)
  5. CH5–CH10: assign switches per the table above
  6. CH5 (ARM): SF 2-position, scaled to match Betaflight arm range
  7. CH6 (RATE): SC 3-position
  8. CH7 (LSPD): SD 2-position
  9. CH8 (RESC): SE momentary (spring return to mid)
  10. CH9 (BUZZ): SH momentary
  11. CH10 (VTX): SA 3-position
  12. Telemetry: enable RSSI and Bat sensor display on main screen
  13. Bind RP2 receiver: hold bind button on RP2 while powering on → TX16S → ELRS menu → Bind

Arm switch safety

The ARM switch (SF) must be configured so that the drone cannot arm accidentally. In EdgeTX: set SF to be a logical switch combined with a throttle-low condition. The drone only arms when SF is down AND throttle is below 5%. This prevents arming mid-flight if SF is accidentally activated.

In Betaflight Configurator → Modes tab: set ARM mode to the SF channel with the appropriate range.

Procedure

Verifying the model after setup

  1. Connect the TX16S to EdgeTX Companion (optional, for backup).
  2. Power on TX16S with drone connected to Betaflight Configurator.
  3. Go to Receiver tab in Betaflight. Move each stick and verify the correct channel responds with the correct direction.
  4. Flip each switch and verify the correct channel changes in the Betaflight receiver tab.
  5. Arm the drone (throttle low, SF down) and verify the ARM indicator appears in Betaflight status bar.
  6. Verify GPS Rescue manual trigger: flip SE momentarily → Betaflight should log a mode change to GPS Rescue in the status bar.

Rationale

Why Wide switch mode and not Hybrid

ELRS Wide switch mode allocates 12 bits to a subset of switches per packet, cycling through all switches over multiple packets. Hybrid mode allocates all switch bits per packet but at reduced per-switch resolution. For libdrone, Wide mode is preferred because the ARM switch gets full 2-position resolution on every packet — the arm state is never delayed by the cycling schedule. Switch latency is imperceptible for any non-safety-critical switch. The arm switch is the one where latency matters most, and Wide mode prioritises it.

Connections

requires: [] related: - betaflight-setup - betaflight-profiles - betaflight-gps-rescue leads_to: - betaflight-setup