ExpressLRS Long Range System, Better than Crossfire and R9M?

by Oscar
Published: Last Updated on

ExpressLRS is an open source long range RC system that focuses on range and latency. It’s also way more cost effective compared to TBS Crossfire and Frsky R9M. If you are looking for a cheaper way to start long range flying and prefer open source, check out ExpressLRS.

Why ExpressLRS?

ExpressLRS offers an affordable long range alternative to the popular TBS Crossfire and Frsky R9M. They even claim to outperform these commercial systems in terms of latency as well as range!

ExpressLRS is based on SX127x hardware combined with an ESP8285ESP32 or STM32 MCU for RX and TX respectively. It’s using LoRa modulation, same as ImmersionRC Ghost and Crossfire, that’s why it has noticeably better range than systems that aren’t using LoRa such as TBS Tracer.

The 900MHz version of ExpressLRS runs at a maximum 200Hz update rate, which is higher than Crossfire’s 150Hz. The 2.4GHz version can even run at 500Hz! (up to 1000Hz on custom hardware).

TX and RX modules communicate via the standard CRSF serial protocol (Crossfire) for easy use with Betaflight and OpenTX.

Right now, ExpressLRS is not as user-friendly as Crossfire, but hopefully it will only get better with time. I will surely publish more content around ExpressLRS in the future.

ExpressLRS Github Page: https://github.com/AlessandroAU/ExpressLRS

Getting The Hardware

At the beginning, you had to build your own receiver and transmitter module (yea, not easy), but now you can just buy them off the shelf.

You can build your own receiver and transmitter module from scratch by getting the right components, ordering your PCB and solder those tiny little chips on the board. This is probably the cheapest way, a TX module and receiver costs only $30 and $15-20 respectively to build. See their Github page for more info.

You can also flash the ExpressLRS firmware to existing Frsky R9M hardware. However, the process is irreversible, meaning you can’t flash Frsky firmware back on the hardware. Update: you can now flash Frsky firmware back on R9 hardware if you wish.

The most convenient way is to just buy the receivers and transmitter module that are made for ELRS. They are inexpensive, designed specifically for the ExpressLRS and already loaded with the firmware, so they are basically plug and play.

The transmitter module is compatible with almost all modern radios with JR module bay, such as the Radiomaster TX16S, Jumper T12, T16 and T18, Frsky Taranis etc. Hopefully “Lite” module will be available soon too for smaller radios like the Jumper T-Lite and Frsky X9-Lite.

There are two frequencies available, 900MHz (915/868) and 2.4GHz. Apart from range, the main difference is that the 900MHz system can only do 200Hz update rate, while the 2.4GHz can do 500Hz, even up to 1000hz on custom radio hardware. Unless you are crazy about range, I think 2.4GHz might be more suitable for most people, it still can do some serious range (miles).

915MHz / 868MHz (HappyModel)

Product Page:

Here are the specs of the transmitter module and receiver:

ES915TX Transmitter Module

  • Dimension: 55mm*39mm*13mm(include heat sink)
  • Weight: 23gram (exclude antenna)
  • Antenna connector: SMA
  • VCC input: 5~13v, Recommend 5v~9v
  • RF Frequency Range: 902MHz ~ 928MHz
  • Maximum Output Power: <33dBm(For >27dBm operation, we recommend add a fan for force cooling)

ES915RX Receiver

  • VCC input: 3.7~24v Recommend 5v~12v
  • Operation current: ~100Ma
  • Rx To FC protocol: CSRF
  • RF Frequency Range: 902MHz ~ 928MHz
  • Dimension: 16mm*10mm*3mm
  • Weight: 0.70 gram (exclude antenna)
  • Antenna connector: IPEX4
  • Telemetry output Power: <17dBm

2.4GHz (HappyModel)

Apart from 900MHz, HappyModel is now also making a 2.4GHz system for ELRS. The advantage of 2.4GHz is the much smaller antenna and higher update rates (up to 1000Hz vs 200Hz). Although the range is not going to be as good as the lower frequency 900MHz, but 2.4GHz will still be able to give you a few kilometers of range in ideal condition, that’s more than enough for most people.

Product Page:

Here’s the 2.4GHz ELRS TX module:

Happymodel is making these tiny receivers with built-in antenna (the black tower – that’s the whole antenna) – ELRS PP, EP1 and EP2.

The differences between PP, EP1 and EP2 are the processor (STM32 and ESP8285): PP has STM32, EP1 and EP2 has ESP8285. Performance wise they are similar, but the STM32 chip has a smaller form factor. The other possible difference is that ESP8285 has WiFi capability while the STM32 chip doesn’t.

PP Receiver:

EP1 Receiver:

EP2 Receiver:

Some of these nano receivers has built-in ceramic antenna (the black block), it’s so neat and small, no more antennas hanging out getting chopped by spinning props.

As it’s going to be buried inside the frame, it won’t perform as well as full size antennas when it comes to range. But for some people this is the perfect solution if they are looking for the absolute smallest or simplest build. For example Tiny Whoops would absolutely benefit from such ExpressLRS receivers as range is not a priority but size, weight and convenience.

How to Use?

In Model settings, go down to External RF, and select CRSF. That’s it. Of course there is a lot more info on Github if you want to master this system.

I will be publishing some tutorials in the coming weeks (around May/Jun 2021).

Telemetry Support

Telemetry is constantly being improved, currently supporting at least 14 types of data, including VBAT, current, downlink/uplink LQ and RSSI.

Telemetry screenshots from IntoFPV user Corrado-c.

Range Testing

ExpressLRS is available on both 2.4GHz and 900MHz so some of the tests here are done on different frequencies. Definitely a ton of potential with ExpressLRS by looking at promising test results like these :)

Max Dist. Freq Pkt Rate TX Power Link to DVR
30Km 900M 50HZ 1W https://www.youtube.com/watch?v=SbWvFIpVkto
10Km 2.4G 250HZ 100mW https://youtu.be/dJYfWLtXVg8
6Km 900M 100HZ 50mW https://youtu.be/kN89mINbmQc?t=58
4.77Km 900M 200HZ 250mW https://www.youtube.com/watch?v=k0lY0XwB6Ko
2.28Km 900M 50HZ 10mW https://www.youtube.com/watch?v=qi4OygUAZxA&t=75s

Edit History

  • Feb 2021 – Article created
  • Apr 2021 – 2.4GHz version by Happymodel announced, added info regarding its TX and RX options

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26 comments

Josh 10th June 2021 - 8:22 pm

Hey Oscar,

I am having a problem installing a fan on my ES915TX, I have the red wire for the fan to the “FAN” pin and GND to GND right next to “FAN”. It doesn’t seem to work at any power output. Any guesses why? And do you experience a faint buzz at higher power outputs?

Thank you!

Reply
Oscar 11th June 2021 - 6:29 pm

Sorry, I don’t have the ES915TX, only the 2.4G version.

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Andreas 9th June 2021 - 5:03 pm

Hi, do you no if I can use the smart port on my r9m to telemetry data over the hc-05 bt module, like it work on Frsky firmware? or didn’t elrs use this port? is it still inverted?

Many thanks andreas

Reply
Oscar 9th June 2021 - 5:42 pm

Yes, Frsky receivers’ inverted signals are due to the hardware inverter at the output (NOT software), so you will still need to get the “uninverted” signal from them.

Reply
Denis 3rd June 2021 - 3:26 pm

what are the chances of this being added to the TBS Multi Protocol Module?

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Kraig 14th May 2021 - 6:44 am

Can the ELRS be used on a Spektrum dx9 like crossfire?

Reply
Oscar 14th May 2021 - 11:27 am

Only these opentx compatible radios are supported as you have to flash this firmware for optimal performance: https://github.com/ExpressLRS/ExpressLRS/tree/250-500-race-modes/OpenTX

Reply
Uwe 2nd May 2021 - 3:07 pm

Can the ERLS receiver be connected to FC like Matek wing with SBUS? I am new on this technical things and dont understand it at all. How many canals have this receiver? I never have seen any data about it.
Thanks already for an answer
Uwe

Reply
Oscar 2nd May 2021 - 5:13 pm

the ERLS receivers connect to FC via an UART (TX/RX), in addition to the 5V and GND, total 4 wires.
I am getting these in and I will do a tutorial on it.

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Jeffery Sievers 27th April 2021 - 1:07 am

Another question, I have updated the firmware that just came out, the new 1.0 rc1, I still don’t have gps telemetry. I was under the impression that the new firmware had almost full telemetry?

Reply
Jeffery Sievers 27th April 2021 - 1:04 am

I noticed the update about being able to reflash R9 back on to the receivers, How exactly do I do that?

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MClay 26th April 2021 - 6:28 pm

Hi Oscar. Great article. I’m new to SBUS and ELRS. Do you know if the ELRS receiver connects to a dedicated SBUS pad on the fight controller to does it connect to a regular UART? I guess I’m asking if the receiver output is inverted or not? Thanks!

Reply
Oscar 26th April 2021 - 11:05 pm

Only Frsky’s SBUS/Smartport is inverted, so no, ELRS receivers won’t be inverted.

Reply
kaji331 25th April 2021 - 2:44 am

Do you know any radio controller company will produce an radio controller within native elrs? 2.4 or 900? I wish a radio controller like tango2 but not TBS, it’s elrs! I don’t like JR module.

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Fabio 23rd April 2021 - 11:12 pm

hi Oscar
Even thought i already got a TBS Crossfire, i stili have a R9M Lite pro, and actually i never used it.
I got curios about the express LRS project. Specs sound really intresting.
Some time ago i saw that software for R9m lite pro was “in development”, but now it seems to have disappeared. Do you know anything about it?

Reply
Oscar 24th April 2021 - 11:43 pm

Sorry I am not actually following the development very closely, it’s best to join ELRS’s facebook group and ask the devs there: /groups/636441730280366/

Reply
deeph 21st April 2021 - 1:47 pm

Hi, I owned frsky x10s with internal Access module mod from FrSky and using OpenTx 2.3.11 directly from companiontx. I saw in ELRS LUA that the Pkt. Rate didn’t match with LUA indicator (above right side in LUA). The control to my wing is OK on the bench, but I don’t know if its fly at field.
Do you know if there is a way out for this?

Thanks
deeph

Reply
Aamir 10th April 2021 - 9:19 pm

Hi Oscar, been reading your blog since long. This is my first comment. This expressLRS thing seems too interesting. Is there a way to make a conventional pwm receiver for this system?
Nad also any 8 or 12 channel support rx?
Sorry for bieng a noob, but i am not very tech savy.

Reply
Oscar 11th April 2021 - 11:43 am

I am not too sure at this point, you might need a SBUS to PWM converter or some sort for now. I am sure manufacturers would produce PWM receivers in the future.

Reply
Joseph 8th April 2021 - 12:15 pm

Hi Oscar,
I am running an OPEN TX 2.2.3 with my QX7. Is it possible for me to use the Banggood version of Happymodel ELRS?

Thamk yoy,

Reply
Oscar 8th April 2021 - 8:50 pm

Yea I think QX7 is supported by ExpressLRS, you just run CRSF as external RF module.

Reply
James T. Jordan 7th April 2021 - 3:47 am

I’m a little confused about the R9m firmware upgrade. The R9M is known to be a strictly FRSky module. But once I flash espressLRS to it could it be used in a Radiomaster or a Jumper? Or is this particular path into espressLRS solely for the FRSky ecosystem?

Reply
Colin Uhrich 26th March 2021 - 2:28 am

At the current state of things, could one get a Jumper T-Lite, running open TX 2.3.11(or most current build for ExpressLRS), Wire in the ExpressLRS ES915TX(might need that current boost Lite Module or battery) from HappyModel with paired ES915RX. Because I should be able to attach a crossfire module to it, flash it and make it work. It may be ugly but I kind of want the Jumpter T-Lite and Express LRS.

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Oscar 26th March 2021 - 9:54 am

Hold off for now if you need the Lite module, I’ve heard rumours that Happymodel is making a JR size as well as a lite size, so you won’t have to do any modifications. Release date might be April, but i cannot confirm.

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Felipe Holanda 16th March 2021 - 1:31 pm

Great article as always. Your blog is fantastic!

Happymodel product is a good option, but I think that R9M and R9Slim is a better deal to start in ExpressLRS.
Almost the same price and a very good hardware with powerfull output option.

Reply
Oscar 17th March 2021 - 12:58 pm

That’s a good point. I bet you can even buy second hand R9 hardware quite cheaply these days.

Reply