Unlocking ExpressLRS PWM Receivers' Serial Protocol Magic
One autumn day in October 2025, I stumbled upon a neat trick with my ExpressLRS PWM receiver — turns out, it’s not just for simple servo control. This revelation that PWM receivers can also output digital serial protocols like SBUS and CRSF without extra hardware changed the way I think about RC setups. Let me take you on a journey to unlock these capabilities with some practical steps and tips I've gathered along the way.
TL;DR: ExpressLRS PWM receivers can output SBUS or CRSF serial protocols natively without extra hardware, offering versatile channel and telemetry options for any RC setup.
Discovering Serial Protocols Hidden In PWM Receivers
On October 2nd, 2025, I set out to demystify a feature of ExpressLRS PWM receivers that even seasoned RC pilots often overlook: their ability to natively output digital serial protocols like SBUS and CRSF. Traditionally, if you wanted SBUS output or the CRSF protocol from your receiver, you’d need a dedicated serial receiver or extra hardware. But with the latest ExpressLRS PWM receivers, these advanced protocols are just a few clicks away—no converters or adapters required.
Let’s break down why this is a game-changer. Most people use PWM receivers to drive servos and ESCs directly, especially in fixed-wing models without a flight controller. PWM is simple, reliable, and perfect for direct connections. But as soon as you introduce a flight controller, serial protocols like SBUS and CRSF become invaluable. They streamline wiring—SBUS supports up to 16 channels over a single wire at 100/300Hz, while CRSF offers up to 16 channels plus bi-directional telemetry over just two wires. This means less clutter, easier setups, and access to advanced telemetry data.
What truly sets ExpressLRS PWM receivers apart is that enabling SBUS or CRSF doesn’t disable the remaining PWM outputs. Even when you repurpose channels for serial output, the other PWM ports remain fully functional. For example, on models like the Radiomaster ER3Ci, ER4, ER5A, ER5C, ER5Ci, ER5V2, ER6G, and ER6GV, you can assign Channel 2 as “Serial TX” and Channel 3 as “Serial RX” via the receiver’s Web UI—while still using Channel 1 for throttle or Channel 4 for yaw. This unlocks a level of flexibility that was previously impossible without extra gear.
Here’s a quick comparison:
- PWM Output: Best for direct servo/ESC control, especially in simple fixed-wing builds.
- SBUS Output: Up to 16 channels on one wire, ideal for flight controllers and streamlined wiring.
- CRSF Protocol: Bi-directional, supports telemetry, and up to 16 channels—perfect for advanced setups.
"Unlocking serial protocols on PWM receivers opens a new chapter in RC flexibility." – Oscar Liang
With ExpressLRS, you’re no longer limited by hardware. Whether you’re flying a basic glider or a telemetry-rich FPV quad, these hidden serial protocol features let you adapt your setup without compromise—making the most of every channel and every wire.
Step-by-Step: Configuring PWM Channels for Serial Output
When I first discovered that ExpressLRS PWM receivers could double as serial protocol transmitters—without any external serial converter—I was genuinely excited. This feature unlocks a whole new level of flexibility, especially for receivers like the ER3Ci, ER4, ER5A, ER5C, ER5Ci, ER5V2, ER6G, and ER6GV, which don’t have dedicated serial ports. Here’s how you can easily configure PWM channels for serial output using the ExpressLRS WebUI:
- Enable WiFi mode on your receiver. You can do this either by running the ExpressLRS LUA script on your radio or simply waiting 60 seconds after powering up—the receiver will auto-activate WiFi mode.
- Connect to the “ExpressLRS RX” WiFi network. Use your laptop or phone to join the network, then open your browser and go to
10.0.0.1to access the ExpressLRS WebUI. - Remap PWM channels for serial output. In the PWM Output settings, set Channel 2 as “Serial TX.” Channel 3 will automatically become “Serial RX.”
- Select your desired serial protocol. The WebUI offers a range of options:
- CRSF protocol
- SBUS output (regular or inverted)
- MAVLink
- HoTT Telemetry
- DJI RS Pro
- SUMD
- Click Save. Your configuration is now active! The receiver will output your chosen serial protocol via the repurposed PWM channels, while the remaining PWM outputs continue to function as normal.
“Using the Web UI to remap outputs made enabling serial straightforward—no extra gear needed.” – Oscar Liang
This approach is perfect for models where you want to keep some servos or ESCs on direct PWM control, while also sending serial data to a flight controller or telemetry device. I validated SBUS output with my ToolKitRC MC8 Battery Checker, confirming signal integrity across both PWM and serial outputs. The process is seamless, and you can switch protocols or revert to full PWM at any time—all through the WebUI.
| PWM Channel | Function When Repurposed |
|---|---|
| CH2 | Serial TX |
| CH3 | Serial RX |
| Supported Protocols |
|---|
| SBUS (inverted/regular) |
| CRSF |
| MAVLink |
| HoTT Telemetry |
| DJI RS Pro |
| SUMD |
With ExpressLRS WebUI, PWM channel configuration for serial output is simple, powerful, and requires no extra hardware—just a few clicks and you’re ready to go.
Dedicated Serial Ports: The ER6G and Friends Simplify Everything
One of the standout ELRS features that truly elevates the latest generation of PWM receivers is the inclusion of dedicated serial ports. Take the RadioMaster ER6G as a prime example: this 2.4GHz receiver comes with RX and TX pins clearly marked, making it effortless to output digital serial protocols like SBUS or CRSF without sacrificing any PWM channel configuration.
When I first got my hands on the ER6G, I was immediately struck by how much simpler it made my builds. Instead of repurposing PWM outputs for serial communication, I just connected my flight controller’s UART directly to the ER6G’s dedicated serial port. No guesswork, no compromise—just pure convenience. As I often say:
"Having dedicated serial ports makes configuration a breeze — plus no loss of PWM channels." – Oscar Liang
Enabling serial protocols on these receivers is almost too easy. Here’s the process I follow:
- Power on the ER6G (or similar receiver with dedicated serial pins).
- Enable WiFi mode—either with the ExpressLRS LUA script or by waiting 60 seconds for auto-activation.
- Connect your device to the “ExpressLRS RX” WiFi network and open
10.0.0.1in your browser. - In the Web UI, select your preferred serial protocol (SBUS, CRSF, etc.), choose between inverted or uninverted output, and click Save.
That’s it—no need to reassign or lose any PWM outputs. The ER6G still provides all six PWM channels for servos or ESCs, while the serial port handles your flight controller’s input. This is a huge advantage, especially for complex builds or when you want to keep your wiring clean and logical.
Other receivers like the Matek R24-P6 also shine here, offering six PWM outputs, high-voltage support (2-8S VBat up to 34V), and preloaded ELRS v3.0 firmware. These options reduce complexity and make integrating with flight controllers that require serial input a breeze.
What I love most is the flexibility: you can still experiment with different serial protocols or even mix serial and PWM outputs as your setup evolves. For anyone serious about maximizing their PWM receiver capabilities, dedicated serial ports are a game-changer—no more trade-offs, just seamless integration and full channel availability.
The Finer Details: Inverted SBUS, Flight Controllers, and Protocol Tweaks
When I first unlocked SBUS output from my ExpressLRS PWM receivers, I quickly realized that the real magic lies in understanding how these digital serial protocols interact with different flight controllers. ExpressLRS PWM receivers are incredibly flexible, but to get flawless telemetry power and control, you need to match your protocol settings—especially SBUS inversion—to your specific flight controller.
Let’s start with the basics: Non-PWM ExpressLRS receivers default to CRSF protocol, which is bi-directional and supports rich telemetry. If you want to use SBUS output instead, you’ll need to configure this manually. My full SBUS output tutorial walks you through the process, but the key detail is choosing the right SBUS inversion mode for your flight controller.
- F4 Flight Controllers: These typically require inverted SBUS on a dedicated SBUS pad. The pad has a built-in inverter, so sending a regular (uninverted) SBUS signal won’t work—your channels may not map correctly, or telemetry could fail.
- F7 Flight Controllers: These are more forgiving. F7 boards natively support both inverted and uninverted SBUS signals on any UART RX pad. This means you can select either SBUS output mode in the ExpressLRS Web UI and it will just work.
Why does this matter? If you get the inversion wrong, you might see channel errors, missing controls, or even a total lack of telemetry. As I always say:
"Matching the inversion settings of SBUS to your flight controller is crucial for reliable operation." – Oscar Liang
ExpressLRS makes this easy. In the receiver’s Web UI (accessed via WiFi mode), you’ll find options to select SBUS or CRSF, and to toggle SBUS inversion. This ensures your ExpressLRS protocol output matches your flight controller’s needs, maximizing both control and telemetry power.
Here’s a quick reference table:
| Flight Controller | SBUS Pad | UART RX Pad |
|---|---|---|
| F4 | Inverted SBUS | Uninverted SBUS (not recommended) |
| F7 | Either | Either |
Getting these finer details right means your ExpressLRS PWM receiver will deliver reliable, low-latency control and full telemetry—no matter your setup.
Beyond Setup: Community Insights, Tools, and The Future of ELRS
As I reflect on the journey of unlocking ExpressLRS PWM receivers’ serial protocol magic, it’s clear that the story doesn’t end with setup. The real excitement comes from the vibrant RC community, the diagnostic tools we rely on, and the rapid pace of innovation that keeps ExpressLRS (ELRS) at the cutting edge.
Community feedback is at the heart of every meaningful improvement. I was reminded of this when Kornel, a reader, reached out about connecting external SBUS telemetry devices to gather more data directly on the transmitter. This kind of curiosity and engagement not only helps refine how we use ELRS features but also inspires the developers to push boundaries. As I often say,
“Community curiosity and feedback propel RC tech to new heights.” – Oscar Liang
Having the right tools is just as important as having the right ideas. The ToolKitRC MC8 has become my go-to for verifying PWM, PPM, and SBUS signals. It’s a simple yet powerful device for battery checking and signal testing, making RC troubleshooting and optimization much less daunting. Tools like this empower us to experiment confidently, knowing we can quickly diagnose and solve issues as we push our setups further.
Meanwhile, the FPV world keeps evolving. Recent releases like the DJI Osmo Nano and the BetaFPV Pavo Pico II—now the smallest cinewhoop supporting DJI O4 and O4 Pro—show just how far miniaturization and compatibility have come. These innovations reflect the same spirit that drives ExpressLRS: making advanced features accessible and user-friendly for everyone.
ExpressLRS receivers themselves are a testament to ongoing progress. With the intuitive ExpressLRS WebUI, configuring PWM receivers for SBUS, CRSF, or even MAVLink is just a few clicks away. The ability to mix serial and PWM outputs without extra hardware means more flexibility for every RC pilot. As new firmware and hardware roll out, I’m excited to see how much further we can go—especially as community-driven ideas continue to shape what’s possible.
So, whether you’re integrating telemetry, testing signals with the ToolKitRC MC8, or exploring the latest FPV gear, remember that experimenting is key. The future of ELRS is bright, and with each new feature and community insight, we unlock even greater performance and possibilities for our RC adventures.
