voxl-elrs

Overview

voxl-elrs source code ExpressLRS Project Page

What is ExpressLRS?

ExpressLRS (ELRS) aims to provide the best completely open, high refresh radio control link while maintaining a maximum achievable range at that rate with low latency. Vast support of hardware in both 900 MHz and 2.4 GHz frequencies using the crossfire protocol.

What is voxl-elrs?

voxl-elrs is an application introduced in VOXL SDK 1.0.0 which gives a user the ability to flash a receiver or transmitter, put a receiver into bind mode, and get device information from a receiver.

There is a large array of ELRS compatible receivers and transmitters on the market and we haven’t tested them all, but below is a list of some that we know voxl-elrs supports.

In theory, voxl-elrs supports any receiver that is compatible with ELRS, however some functionalities such as setting a receiver into bind mode may be deprecated since this action requires firmware modifications. Here is a list of currently supported receivers and transmitters:

Binding Procedure

Note: Ensure that voxl-elrs version is 0.0.8+ and that both the receiver and transmitter are on ELRS version 3.0.0+!

Usage

Currently, voxl-elrs does not require any configuration in order to get started. Usage is as follows:

voxl2:/$ voxl-elrs -h
Description: Flash a RX or TX with ELRS firmware.

Usage: voxl-elrs -h -d -w -q -b -u -v -s

Optional Arguments:
 -h, --help              Show this help message and exit
 -d, --device            Serial port to use for flashing
 -w, --wizard            Activate interactive wizard
 -q, --quiet             Quiet mode, don't print msgs
 -b, --bind              Put receiver in bind mode
 -u, --unbind            Unbind a receiver
 -v, --version           Get receiver version information
 -s, --scan              Scan receiver for firmware information

Argument Descriptions:

• -h/–help: Show the help message and exit.
• -d/–device: Specify a specific serial port to use when flashing a receiver or transmitter. By default, this will be set to /dev/ttyUSB0 if flashing a transmitter and /dev/slpi-uart-7 when flashing a receiver through voxl2.
• -w/–wizard: Activate the interactive wizard that provide user options.
• -q/–quiet: Quiet mode, don’t print out any messages. Voxl-elrs program will not print out any messages but underlying programs that are called may still print some messages.
• -b/–bind: Set a receiver that has been flashed with ModalAI firmware into bind mode.
• -u/–unbind: Unbind a receiver that has been flashed with ModalAI firmware.
  • Note: Unbind option only available in SDK 1.0.1+ and voxl-elrs version 0.0.9+.
• -v/–version: Get version information from a receiver. This includes receiver name (Ex: BetaFPV 900RX) and firmware version (Ex: 3.2.1.1).
• -s/–scan: Scan a connected receiver for firmware information, automatically update to latest firmware if detected version is out of date.

Wiring Guide

BetaFPV Nano RX

FrSky R9MM/Mini-OTA

Manually flashing a receiver

• In order to manually flash an ELRS receiver, make sure that the receiver is not in bootloader mode and that it is not connected to a transmitter. These conditions are necessary so we can get device information from the receiver.
• On host computer adb shell onto the voxl2 or ssh:

  adb shell
  OR
  ssh root@<voxl2 ip> 
  

  Note: The default ssh password is oelinux123

• Now, on the voxl2 use the voxl-elrs wizard and select the “Flash Receiver” option:

  voxl2:/$ voxl-elrs -w
  Select an option:
  [1] Quit
  [2] Flash Receiver
  [3] Flash Transmitter
  [4] Unbind Transmitter
  [5] Bind Mode
  [6] Device Info
  [7] Recover Receiver
  2
  

• Select which receiver you are flashing:

  Select an option:
  [1] Quit
  [2] Auto-detect
  [3] BetaFPV Nano RX
  [4] FrSky R9MM/Mini
  

• The receiver you selected will now be flashed with the latest firmware!
  

Recovering a bricked receiver

• Manually place the receiver into bootloader mode by holding down the boot button while power cycling the receiver.
  
• On host computer adb shell onto the voxl2 or ssh:

  adb shell
  OR
  ssh root@<voxl2 ip> 
  

• Now, on the voxl2 use the voxl-elrs wizard and select the “Recover Receiver” option:

  voxl2:/$ voxl-elrs -w
  Select an option:
  [1] Quit
  [2] Flash Receiver
  [3] Flash Transmitter
  [4] Unbind Transmitter
  [5] Bind Mode
  [6] Device Info
  [7] Recover Receiver
  7
  

• Select which receiver you are recovering:

  Select an option:
  [1] Quit
  [2] Auto-detect
  [3] BetaFPV Nano RX
  [4] FrSky R9MM/Mini
  

  Note: As of 09/07/2023 only recovery for BetaFPV Nano RX is available

• Follow the instructions given and if the recovery is successful you should see an output like the image below
  

• If the recovery process fails, double check that the receiver is actually in bootloader mode. Make sure that you hold the bootloader button down for a couple seconds after power cycling the receiver.

Voxl-configure-elrs

voxl-configure-elrs is an application introduced in voxl-elrs v0.1.1 (available after SDK 1.0.0) which gives a user the ability to configure PWM channels on a PWM capable receiver. Input channels from a transmitter or other controller (such as a steam deck) can be assigned to a PWM output channel. The number of output PWM channels is limited to the amount of exposed PWM capable pins on a particular receiver.

Usage

voxl2:/$ voxl-configure-elrs --help 
Description: Configure ELRS receiver PWM channels.

Usage: voxl-configure-elrs -h -w -o -d -c

Optional Arguments:
 -h, --help              Show this help message and exit
 -w, --wizard            Activate interactive wizard
 -o, --off               Disable PWM output on all pins
 -d, --default           Set PWM input channels to default values
 -c, --custom            Set PWM input channels to custom values

Argument Descriptions:

• -h/–help: Show the help message and exit.
• -w/–wizard: Activate the interactive wizard that provide user options.
• -o/–off: Disable PWM output on all pins
• -d/–default: Set PWM input channels to ModalAi factory default values.
• -c/–custom: Set PWM input channels to user defined values.

PWM Capable Receivers

FrSky R9MM/Mini-OTA PWM outputs

Tips

• In order for a receiver and transmitter to bind, they need to be on the same major version of ELRS. For voxl-elrs, this means that both the transmitter and receiver need to be on ELRS version 3.0.0+.
• The recommended usage of this tool is to use the interactive wizard, by either using voxl-elrs -w or voxl-elrs --wizard and then following the prompt.
• If you just want to bind a transmitter to your receiver, you can use the voxl-bind-elrs helper utility which will set the receiver into bind mode without having to use the wizard.
  • Note: You cannot set a receiver into bind mode if it is actively connected to a transmitter. Turn the transmitter off or unbind the receiver and then run either voxl-bind-elrs, voxl-elrs --bind, or run the wizard and follow the prompt for bind mode.
• If making your own custom modifications to the receiver firmware, be careful using the voxl-elrs --scan function. If voxl-elrs detects a firmware version that doesn’t match the latest for that version of voxl-elrs, it will overwrite the firmware you have currently loaded.
• You can determine the state of the receiver by inspecting the LED on your receiver and comparing to the information on the ELRS LED Status page.
• Useful information regarding all things ExpressLRS (ELRS) can be found on the ELRS quickstart page.