ExpressLRS Firmware Updating and Binding

So, you picked up the RadioMaster Pocket ELRS transmitter and hopefully one (or more!) 2.4GHz Receivers.  Or maybe you need a little help picking a receiver to match what you’re flying?  If so, you’re in the right place.

What is ExpressLRS?

ExpressLRS is a radio protocol that allows your radio to talk to a matched receiver.  In order to control your model, whether that be a plane or a multirotor, the transmitter needs to send those commands to the receiver, located in or on your model.  In order for that to work, the receiver needs to go through the “BIND” procedure to know what transmitter it’s talking to.

Binding Methods for ExpressLRS

There are currently three different methods of binding your ExpressLRS receiver to your RadioMaster Pocket ELRS transmitter:

1. Traditional Method: Power the receiver on/off three times.  Receiver will enter bind mode on the third power up.  Use the “Bind” function in the ExpressLRS LUA Script to bind.

2. Binding Phrase: When you update the firmware on your transmitter and receiver, you have an option to create a unique binding phrase.  They need to match on both in order for this to work.  Binding happens automatically at startup.

3. On firmware’s 3.4.0 and above, along with Betaflight 4.5.0+ and Betaflight Configurator 10.10.0+, you can initiate a bind request in Betaflight from the Receiver tab or the CLI tab

Note: If you have attempted one or more of these methods and the receiver will not bind to the transmitter, you most likely will need to update.  See below.

Why Update?

Updating your transmitters and receivers achieves three things:

1. Getting any safety and reliability bugs addressed as they are found.  This makes your flying safer and limits frustrations when things don’t work as they should.

2. Getting the latest features!  New things are being added all the time.  Using these features, especially as they are integrated with other software, such as Betaflight, can be time savers and give you new options with your aircraft.

3. Compatibility.  Receivers not on the same or close firmware as the transmitter will not bind with each other.  If you are having problems binding, check this first!                          

Getting Started

So, what do you need to do to get started? To start off, we need to know what you’re going to be flying.

If you’re flying a multirotor with space to mount an antenna:

• RadioMaster RP1 V2 ExpressLRS 2.4ghz Nano Receiver

If you want a built in antenna or a smaller multirotor with no where to mount an antenna:

• RadioMaster RP2 V2 ExpressLRS 2.4ghz Nano Receiver

If you are flying fixed wing and need a PWM receiver:

• RadioMaster ER5A 2.4GHz 5 Channel ELRS PWM Receiver

• RadioMaster ER6 2.4GHz 6 Channel ELRS PWM Receiver

• RadioMaster ER8 2.4GHz 8 Channel ELRS PWM Receiver

The RP1 and RP2 are very similar, with the exception of the RP1 having an antenna that can be mounted away from the receiver, and the RP2 has a built-in antenna tower. 

The differences between the PWM receivers comes down to the amount of channels available for your servos.

Make sure you select the correct one!  If you’re unsure, feel free to reach out to us and ask!

Also, for the duration of this article, we’re going to be using the RadioMaster Pocket ELRS transmitter to work with the ExpressLRS receivers.

Download ExpressLRS Configurator and Betaflight Configurator

Before we can get started let’s gather all the tools we need to have available:

• ExpressLRS Configurator - Version 1.6.1 (Latest at time of writing)

• Betaflight Configurator - Version 10.10.0 (Latest at time of writing)

These tools will allow us to perform updates to both the transmitter and receiver, along with helping us with the binding process.

Updating the Transmitter

In order to take advantage of all the latest benefits of newer firmware, let’s go ahead and update the transmitter to the latest version of the ExpressLRS firmware.  Let’s start by preparing the radio for ExpressLRS.

System Setup

This will prep the operating system of the radio for ExpressLRS:

• Turn on your RadioMaster Pocket by holding down the Power Button for a few seconds

• Press the “SYS” button on the left of the speaker

• Press the “PAGE>” or “PAGE<” button until you get to the Hardware page

• Scroll down until you get to the “Internal RF” section

• Scroll to “Type”. If not already set, press down on the scroll wheel to select (it should click, this is your enter button) and change “Type” to “CRSF”.  Press enter to confirm and save

• Change the “Baudrate” to “400k”

  • Note: You can leave it at the “5.25m”, however the 400k is the most stable and recommended.  If you would like to test the higher baud rates, do so at your own risk.  Just be on the lookout for consistent “Telemetry Lost” and “Telemetry Recovered” notifications from your radio at ranges where you should have good signal

• Scroll down to “ADC filter” and press enter to remove the check mark and turn it off

• Press the “RTN” button until you are back at the main page.

Model Setup

You will need to complete this for each model that you want to utilize ExpressLRS with.  You can do this with existing models as well as new ones as long as your physical models have been equipped with an ExpressLRS receiver.

• Press the “MDL” button on the right side of the speaker

• Press the “Page>” button once to take you to the Setup menu

• Scroll down to the “Internal RF” section

• Scroll to Mode and select “CRSF”

  • Note: There will be a number after the “CRSF” indicating the baud rate that you set up in the above directions.

• You can also give your model a unique number by scrolling down to “Receiver” and changing the number.

Updating the Firmware

Updating the firmware on the transmitter is easy but can seem like a daunting task.  But in order to take advantage of some of the newest features, we want to be on the latest version of ExpressLRS.  Don’t worry, we’ll go through it step-by-step to ensure a smooth update:

• Open up the ExpressLRS Configurator on your computer

• You should be on the “Configurator” tab visible to the left of the window

• Under the “Releases” drop down, select the highest version (3.4.2 at the time of writing)

  • Note: You can test out Pre-Release if you so choose, however they are often for bug checking and cutting-edge features that may not be stable yet.  

• Under the “Target” heading there will be two drop-down boxes.  Under “Device Category” select “RadioMaster 2.4GHz”

• Under “Device”, select “RadioMaster Pocket Internal 2.4GHz TX”

• Under “Flashing Method” select WiFi

• Under “Device Options” there are several different options here.  Let’s work through these:

  • Under “Regulatory Domains” select “Regulatory_Domain_ISM_2400” if you are located anywhere besides the European Union.  If you are in the EU, then you would select “Regulatory_Domain_EU_CE_2400”

  • Under “Binding Phrase Setup” you can check the box if you would like to simplify your binding process.  Here you would enter a simple word or string to aid in binding and to minimize conflict when flying with others using the ExpressLRS ecosystem.  

    • Note: This will set a passcode of sorts that you can then flash onto your receivers to aid in instant binding.  This passcode will be visible, so do not use a password that you use on secure websites.  Be unique here, as the more unique, the lower the chance that someone that you fly with will have the same passcode, thus creating binding problems.

    • Note: If you do use the passcode, you will need to update the firmware on every receiver in order to assign that passcode.  Otherwise, your binding process will not be automatic, and will take a different procedure which we will outline later.

  • Under “Compatibility Options” ensure that “UART_INVERTED” is checked

  • Under “Extra Data” ensure that “TLR_REPORT_INTERVAL_MS” is not checked

  • Under “Network” here you can input your home WiFi name and password.  Make sure to spell both correctly, it will save having to go through re-flashing later

    • Note: After the first flash, the extra steps of needing to connect directly to the transmitter can be skipped and flashes can happen automatically.  More on that during the flashing process below.

    • Note: Leave “AUTO_WIFI_ON_INTERVAL” at 60

• Now that all our settings are applied, go ahead and click the “BUILD” button at the bottom left.

  • Once that’s complete, a window should pop up with a file called “firmware.bin”.  This is the firmware that we will use to update the transmitter.  Do not close this window, the file can be difficult to locate as it’s buried in a temp folder.  Don’t worry, your system will clean these out fairly regularly.

• Power on your RadioMaster Pocket

• Press the “SYS” button to the left of the speaker.  You should be in the “TOOLS” menu

• Use the scroll wheel to navigate to the “ExpressLRS” tool and press down on the scroll wheel to load the tool.  Give it a few seconds to load.  

  • Note: If it’s stuck on the loading screen, then your Internal RF module is not turned on in the model you are currently using.  Press and hold the “RTN” button to exit back to the main screen.  Go back up to the “Model Setup” section above for help turning it on, then come back here.

• Use the scroll wheel to navigate down to “WiFi Connectivity” and press the scroll wheel to enter the submenu.

• Press the scroll wheel again on “Enable WiFI”

  • A window will appear on the transmitter screen that says “WiFi Running…”

• On your computer or laptop, connect your WiFi network to the “ExpressLRS TX” network.  The password is “expresslrs”

• A browser window should automatically open but if not, open up a browser window and type “10.0.0.1” in the address bar.

• This will open up the ExpressLRS Web User Interface

• Click on the “UPDATE” tab

• Drag and drop the “firmware.bin” file into the box and the Web UI will proceed with flashing the firmware.

• Once the flashing is complete, you will see an “Update Succeeded” box pop up.

• Your RadioMaster Pocket will automatically exit WiFi mode and return to the WiFi Connectivity submenu.  Press and hold the “RTN” button to exit back to the main screen.

• Congratulations!  You have successfully updated your RadioMaster Pocket!  Future updates will be made much easier if you entered your Home WiFi information, as you will be able to flash directly from the ExpressLRS Configurator.  If you did not, you will need to follow the above directions each time.

Updating RadioMaster Receivers

Updating the receivers for the first time will follow a similar instruction set as the transmitter.  It’s a very simple process and by following the steps below, you will be able to accomplish it in no time.  Let’s get started!

Wiring Your Receiver

Wiring of the RP1 or RP2 to a flight controller is relatively straightforward.  First, you want to find a section of the flight controller where you have access to the following pads and that will provide power to those pads when the USB is attached to the flight controller (you can test this using a multimeter and plugging in your FC to USB and probing the 5v and ground pads): 

• Ground

• 5v

• TX

• RX

You’ll notice on the RP1/2 you’ll have those same markings.  You want to wire up the receiver as follows: 

• Receiver Ground > Flight Controller Ground

• Receiver 5V > Flight Controller 5V

• Receiver TX > Flight Controller RX

• Receiver RX > Flight Controller TX

Note: Double check again before you solder that the RECEIVER TX is going to the FLIGHT CONTROLER RX and that the RECEIVER RX is going to the FLIGHT CONTROLLER TX.

Note: If your Flight Controller does not have a pad that is powered under USB, you can use a battery to power your system.

Note: If you are using one of the PWM Receivers, you’ll just need to be able to hook it up to an ESC with BEC capable of anywhere between 4.5v and 8.4v.

Updating Using Auto WiFi Mode

One of the nice things about the ExpressLRS receivers is that when they don’t detect any signal coming from a bound transmitter, they will automatically turn on the built-in WiFi in order to be flashed.  This is convenient when you want to set up that unique binding phrase to make binding a very simple process.  Let’s get started.

• Open up the ExpressLRS Configurator on your computer

• You should be on the “Configurator” tab visible to the left of the window

• Under the “Releases” drop down, select the highest version (3.4.2 at the time of writing)

  • Note: You can test out Pre-Release if you so choose, however they are often for bug checking and cutting-edge features that may not be stable yet.  

• Under the “Target” heading there will be two drop-down boxes.  Under “Device Category” select “RadioMaster 2.4GHz”

• Under “Device”, select “RadioMaster RP1 2.4GHz RX”

  • Note: If flashing a different receiver, make sure to select that specific receiver to avoid any issues.  

    • Example: You want to update your ER6 receiver, select “RadioMaster ER6 2.4GHz Diversity+6xPWM RX”.  Also note that there can be several options to select from withing the ER6 Category.  Make sure you select the right one.  READ CAREFULLY!

• Under “Flashing Method” select WiFi

• Under “Device Options” there are several different options here.  Let’s work through these:

  • Under “Regulatory Domains” select “Regulatory_Domain_ISM_2400” if you are located anywhere besides the European Union.  If you are in the EU, then you would select “Regulatory_Domain_EU_CE_2400”

  • Under “Binding Phrase Setup” you can check the box if you would like to simplify your binding process.  Here you would enter a simple word or string to aid in binding and to minimize conflict when flying with others using the ExpressLRS ecosystem.  

    • Note: This will set a passcode of sorts that you can then flash onto your receivers to aid in instant binding.  This passcode will be visible, so do not use a password that you use on secure websites.  Be unique here, as the more unique, the lower the chance that someone that you fly with will have the same passcode, thus creating binding problems.

  • Under “Compatibility Options” ensure that “RCVR_UART_BAUD” is not checked unless you are working with a KISS V1 Flight controller.  If you are, put your mouse pointer over the question mark for more information.

  • Under “Performance Options” ensure that “LOCK_ON_FIRST_CONNECTION” is checked.

  • Under “Network” here you can input your home WiFi name and password.  Make sure to spell both correctly, it will save having to go through re-flashing later

    • Note: After the first flash, the extra steps of needing to connect directly to the transmitter can be skipped and flashes can happen automatically.  More on that during the flashing process below.

    • Note: Leave “AUTO_WIFI_ON_INTERVAL” at 60

• Now that all our settings are applied, go ahead and click the “BUILD” button at the bottom left.

  • Once that’s complete, a window should pop up with a file called “firmware.bin.gz”.  This is the firmware that we will use to update the transmitter.  Do not close this window, the file can be difficult to locate as it’s buried in a temp folder.  Don’t worry, your system will clean these out fairly regularly.

    • Do not unzip or extract this file.  We will use it just as it is.

• Power down your RadioMaster Pocket if it was powered up.

• Provide power to your receiver either by plugging in the USB or battery.  It should be flashing slowly at first, but after 60 seconds it will start flashing very fast.  This means the receiver has entered into “Auto WiFi Mode”.

• On your computer or laptop, connect your WiFi network to the “ExpressLRS RX” network.  The password is “expresslrs”

• A browser window should automatically open but if not, open up a browser window and type “10.0.0.1” in the address bar.

• This will open up the ExpressLRS Web User Interface

• Click on the “UPDATE” Tab

• Drag and drop the “firmware.bin.gz” file to the box and the receiver will begin the flashing process.  Do not disconnect the power.

• Once complete, you will see the following window:

• Once the LED starts flashing slowly again, you can now remove power to the receiver.

• Congratulations!  You have successfully updated your RadioMaster receiver!  Future updates will be made much easier if you entered your Home WiFi information, as you will be able to flash directly from the ExpressLRS Configurator.  If you did not, you will need to follow the above directions each time.

• If you utilized the Binding Phrase, once you power up the RadioMaster Pocket then power the receiver, binding should happen quickly and automatically!

Update Using Betaflight

You can also use Betaflight to update the RadioMaster RP1 and RP2 once you have them wired up to the board.  Some might find this an easier method over the Auto WiFi, however it does require setting up the receiver within Betaflight.  It’s easy though, so let’s get started.

• Make sure you have wired the RadioMaster RP1 / RP2 to the flight controller using the instructions above.

• Connect a USB from your computer to the flight controller.  If you have wired the receiver to the flight controller on a voltage pad that is powered by USB, your receiver should start blinking.  

• Open up Betaflight and click the “Connect” button at the top right.

• Betaflight will connect up to the flight controller and you should be at the setup screen

• On the left you will see the tabs for navigating to different key features within Betaflight.  Take a moment to familiarize yourself, as we’re going to move through a few of these to get the receiver ready for an update.

• Click on the “Ports” tab.

• If the pads on your flight controller are labeled, identify the UART that your RX and TX wires are soldered to.  Example: if the pad is labeled TX2 and RX2, then you are soldered to UART2.

  • If your pads are not labeled, you will need to find a pinout diagram of the pads.  These sometimes come with the Flight Controller, but if not, head to the manufacturer's website.

• Within the “Ports” tab, you will see a list of the UARTs.  On the UART you soldered the receiver to, you will want to turn “Serial Rx” on.

• Click the “Save and Reboot” button at the bottom left

• Click the connect button at the top right if Betaflight does not reconnect automatically.

  • If you would like to have this functionality, turn on “Auto-Connect” before connecting.

• Click on the “Receiver” tab

• On the right side of the screen is the “Receiver” section

• In the “Receiver Mode” drop-down, select “Serial (via UART)”

• In the “Serial Receiver Provider” drop-down, select “CRSF”

• Click the “Save and Reboot” button at the bottom right

• Click “Disconnect” if Betaflight connects back up to the flight controller

• Unplug the flight controller for now

• Close Betaflight.  We don’t want it interfering with the COM port when we go to flash the receiver.

From here, we’re going to move into the ExpressLRS Configurator.  Instead of using WiFi, we will use Flight Controller Passthrough to flash the receiver.

• Open up the ExpressLRS Configurator

• Under the “Releases” drop down, select the highest version (3.4.2 at the time of writing)

• Under the “Target” heading there will be two drop-down boxes.  Under “Device Category” select “RadioMaster 2.4GHz”

• Under “Device”, select “RadioMaster RP1 2.4GHz RX” or “RadioMaster RP2 2.4GHz RX”

  • Note: If flashing a different receiver, make sure to select that specific receiver to avoid any issues.  

• Under “Flashing Method” select “BetaflightPassthrough”

• Under “Device Options” there are several different options here.  Let’s work through these:

  • Under “Regulatory Domains” select “Regulatory_Domain_ISM_2400” if you are located anywhere besides the European Union.  If you are in the EU, then you would select “Regulatory_Domain_EU_CE_2400”

  • Under “Binding Phrase Setup” you can check the box if you would like to simplify your binding process.  Here you would enter a simple word or string to aid in binding and to minimize conflict when flying with others using the ExpressLRS ecosystem.  

    • Note: This will set a passcode of sorts that you can then flash onto your receivers to aid in instant binding.  This passcode will be visible, so do not use a password that you use on secure websites.  Be unique here, as the more unique, the lower the chance that someone that you fly with will have the same passcode, thus creating binding problems.

  • Under “Compatibility Options” ensure that “RCVR_UART_BAUD” is not checked unless you are working with a KISS V1 Flight controller.  If you are, put your mouse pointer over the question mark for more information.

  • Under “Performance Options” ensure that “LOCK_ON_FIRST_CONNECTION” is checked.

  • Under “Network” here you can input your home WiFi name and password.  Make sure to spell both correctly, it will save having to go through re-flashing later

    • Note: After the first flash, the extra steps of needing to connect directly to the transmitter can be skipped and flashes can happen automatically.  More on that during the flashing process below.

    • Note: Leave “AUTO_WIFI_ON_INTERVAL” at 60

• Double check to ensure that Betaflight is closed and your transmitter is off.

• Plug in the flight controller.

• Click the flash button at the bottom left.

• The screen will change over to the flashing screen, and once complete you will get a “Success!” at the bottom.

• Flashing is now complete!

Binding the Receiver

Binding the ExpressLRS receivers to a transmitter is a very straightforward process.  There are three different methods to binding.

Traditional Binding

• To do this, you need to power the receiver on/off three times.  The receiver will enter bind mode on the third power up.

• Press the “SYS” button on the RadioMaster Pocket

• You should be in the “TOOLS” menu.  Use the scroll wheel to navigate to and select the “ExpressLRS” tool.

• Once loaded, use the scroll wheel to navigate to the “Bind” command.  Press the scroll wheel to initiate binding

• The receiver will stop flashing once bound!

Binding Phrase

• If you flash your transmitter and receiver and set up a Binding Phrase, once you turn on your radio then power up the receiver, they will automatically bind.

• Make sure you choose a unique Binding Phrase!

Binding through Betaflight

On ExpressLRS firmware 3.4.0 and above with Betaflight 4.5.0 firmware on your flight controller and Betaflight Configurator 10.10.0 and above, you can utilize the “Bind Receiver” button in the Receiver tab in Betaflight to initiate a bind call to the receiver.

• Connect your Flight Controller to your computer via USB

• Click “Connect” in the top right corner of Betaflight

• Navigate to the “Receiver” tab

• Click the “Bind Receiver” button in the bottom left corner

• Your receiver will start to flash
• Press the “SYS” button on the RadioMaster Pocket
• You should be in the “TOOLS” menu.  Use the scroll wheel to navigate to and select the “ExpressLRS” tool.
• Once loaded, use the scroll wheel to navigate to the “Bind” command.  Press the scroll wheel to initiate binding
• The receiver will stop flashing once bound!
• You can also type “bind_rx” in the CLI Tab to initiate that same call.