ModalAI Forum

@heiko.lizan

Any elrs radio that's 900mhz or dual band compatible should work when in low band mode. If the transmitter is running v4+ you should be able to downgrade it to v3 following the elrs update guide

It's normal that some services aren't running. You may need to re-enable px4 with systemctl enable voxl-px4

This guide should be what you need to bind: https://docs.modalai.com/voxl-elrs/#binding-procedure

Hi @heiko.lizan can you share the SKU and SDK version that shows up when you adb in? Also the error message when you run voxl-elrs update.

A few issues you may be running into:

1. your Radiomaster Boxer ELRS module is 2.4Ghz only and is not compatible with our 900Mhz drones
2. your Radiomaster Boxer ELRS module is running ELRS 4.0+, you will need to downgrade to the latest ELRS V3 since we are currently not supporting ELRS v4.0+
3. The receiver is stuck in bootloader mode and needs recovered. (will need the error messages to diagnose) It's possible the error messages may provide steps to run to get the receiver to start working again.

Hey, If you're able to update the SDK and run voxl-elrs update it may have some bug fixes to improve reliability.

I would also check that the receiver antenna is still connected and is not damaged as that can significantly reduce the range.

If the transmitter is showing signal but the drone is not responding it's possible you are bound to another transmitter.

before running esptool ensure px4 is disabled with "systemctl status voxl-px4"
if it's still running try disabling it again and rebooting.
It must be disabled from boot for esptool to work.
Then after the update is successful you can re-nable px4 and reboot

Once the update is complete the receiver led should start blinking and the voxl-elrs ping command should respond

@Hector-Gutierrez

It should always be supported, there's instances where an update fails and you'll need to re-enter bootloader mode to fix it.
bootloader mode should be recoverable from the drone. Here's some tips to try and recover it.

this may take a few attempts until you get it right

try these steps to see if it will atleast communicate in bootloader mode. sometimes the esptool can take a minute to respond

• voxl-configure-px4 disable
• Turn off drone
• Hold down the receiver's boot button, Power on the drone while holding the button
• Keep holding for 1-2 second after power on, then release
• receiver led should be solid blue (after following these steps it should be in bootloader mode)
• run this command to check if receiver is alive: "python3 -m esptool --port /dev/slpi-uart-7 --chip ESP8266 --baud 115200 --before no_reset chip_id"
• If that works then proceed with update.
• "python3 -m esptool --port /dev/slpi-uart-7 --chip ESP8266
  --baud 115200 --before no_reset --after soft_reset
  write_flash 0x00 /usr/share/modalai/voxl-elrs/firmware/3.5.3.21/BETAFPV_900_RX_via_UART/BETAFPV_900_RX-3.5.3.21-20251205.bin"

@Hector-Gutierrez hey I've been able to recover almost all of these betafpv receivers. Is the blue led still active or has it gone completely black? Holding the button on power up should force it into bootloader mode with a solid blue light which is a good first step.