You need a way to connect your receiver to your flight control unit, such as FBL, Redundancy Bus, or Gyros. In the early days of gyro stabilization on RC models, it wasn't uncommon to use a "squid" cable of sorts, where you'd take a PWM signal for each channel from the receiver to the gyro. That means at least four, sometimes up to 12+ signal wires in addition to one or two sets of power wires.
These days, however, we have easy access to serial data protocols, which at a minimum send all control channels (usually 16) as well as some other misc. information (such as failsafe status) and, sometimes, telemetry data. This means that with the right hardware, you just need a single 3-wire servo cable to connect from the receiver to your gyro.
So where does it start?
S.Bus
Modern RC-related serial protocols started to gain popularity with S.Bus. Originally coined and engineered by Futaba long ago but now widely adopted by many different radio systems and almost every gyro/flight control system, and even in many areas outside of the RC hobby. S.Bus carries 16 channels from a receiver to a flight control unit, along with several other pieces of information (packet lost, failsafe status, etc). It's a digital protocol, as opposed to PWM, so it's much less susceptible to noise and interference.
FrSky adopted S.Bus many years ago, much to the enjoyment of its users. In combination with their S.Port protocol (more on that later), it was possible to have communication back FROM the flight controller to the receiver, which would then pass any information to the transmitter as new telemetry sensors. S.Bus is also used for redundancy in parts of the FrSky ecosystem. You can, for example, connect the S.Bus input on one receiver to the S.Bus output from a second receiver. If the first receiver loses signal, even momentarily, the S.Bus signal from the second receiver is automatically and seamlessly passed onto the output of the first receiver. You can also use S.Bus with any S.Bus compatible servo, allowing multiple servos to run from the same signal wire but respond to different channels.
Somewhat recently, FrSky has come out with a customized version of S.Bus called SBUS-24. It's more or less the same protocol, but with 8 more channels than typical S.Bus. This makes it incompatible with anything that expects the standard S.Bus 16-channel signal, and so far, only FrSky products have and can use SBUS-24. However, all modern FrSky receivers can output either version of S.Bus, just by changing a setting in the receiver. The default is the standard 16-channel protocol.
The S.Bus protocol runs at 100,000 bits per second.
S.Port
As stated earlier, S.Port is FrSky's original telemetry protocol. Technically, there was one before it, but it's very old and no longer used, so it's not worth explaining further. S.Port is a bidirectional serial data protocol that was designed to connect various telemetry sensors, such as GPS sensors, Voltage/Current sensors, etc to a FrSky receiver. Because it is bidirectional, it allows you to connect sensors in 'parallel' - meaning all of the signal lines are connected together, and each sensor takes turns giving its reading. S.Port is still in use today, and still supported by all modern FrSky equipment.
The S.Port protocol runs at 57,600 bits per second.
F.Port
F.Port was FrSky's first attempt at a single-line control AND telemetry data protocol. It was more or less a direct combination of S.Bus and S.Port. It can carry up to 16 channel worth of data from the receiver to a flight controller, and simultaneously up to 27 sensors and other information from the flight controller to the receiver, to be sent to the transmitter as telemetry sensors. F.Port is only for connection from a receiver to a flight controller, and cannot accept any extra telemetry sensors in parallel nor can it be used on a telemetry sensor by itself. The main reason for this is that F.Port was conceptualized when FrSky was big in the FPV community, and people didn't want to have to run S.Bus and S.Port at the same time because of the extra wiring. Since most of the time any extra sensors would be connected to the flight controller instead, there was no reason to use extra telemetry sensors connected to the receiver itself. Hence, F.Port can only be used for the one specific purpose of RX->FC connection.
The F.Port protocol runs at 115,200 bits per second, just a bit faster than S.Bus and twice as fast as S.Port, meaning telemetry data gets through faster.
F.BUS
F.BUS is FrSky's latest, most advanced serial data protocol. F.BUS actually started out as "F.Port2", but it was very brief before it was modified and renamed to F.BUS. It is like F.Port in that it carries control data and telemetry data bidirectionally on a single line, however, it differs in several ways. F.BUS allows the connection of extra telemetry sensors to the same signal line, just like S.Port. As part of that, F.BUS can be used for not only the receiver to flight controller connection, but also bidirectional signaling for telemetry sensors, servos, ESCs, and more. Whereas S.Bus only allows you to control S.Bus-compatible servos, with F.BUS you can not only control F.BUS-compatible servos but also receive information from them... things like servo current, temperature, etc, as well as being able to program the servo itself for things like rotate direction, travel range, etc. FrSky also has a line of F.BUS-compatible ESCs, meaning you can send throttle control to the ESC while simultaneously receiving telemetry info back from it, such as temperature, current, voltage, etc.
The F.BUS protocol runs at 460,800 bits per second, which is four times as fast as S.Bus/F.Port, and EIGHT times as fast as S.Port, meaning both control and telemetry data can be moved around much more quickly.
BLS5400 Series servos are a perfect match To Utilize SBUS or FBUS Protocols
FAQs About FrSky Sbus and Fbus
What is SBUS and how does it work?
SBUS, originally developed by Futaba, is a digital serial communication protocol widely used in RC models. It allows for the transmission of up to 16 control channels from the receiver to the flight control unit, along with other essential data like failsafe status and packet loss information. SBUS is less susceptible to noise and interference compared to traditional PWM signals, making it a reliable choice for RC enthusiasts. FrSky adopted SBUS and enhanced it with their S.Port protocol, which allows for telemetry data to be sent back from the flight controller to the receiver and then to the transmitter.
What is SBUS Protocol?
SBUS, or Serial Bus, is a digital communication protocol developed by Futaba for use in RC (Radio Control) systems. It has become a popular standard due to its efficiency and reliability in transmitting multiple channels of control signals from a receiver to a flight control unit or other devices.
Key Features of SBUS Protocol:
Multiple Channel Support: SBUS can carry up to 16 control channels over a single signal wire, significantly reducing the wiring complexity compared to traditional PWM signals which require a separate wire for each channel.
Digital Transmission: As a digital protocol, SBUS is less prone to noise and interference, ensuring a more reliable connection between the receiver and the flight controller or servos.
Telemetry Integration: When used in conjunction with FrSky's S.Port protocol, SBUS can facilitate bidirectional communication, allowing telemetry data from the flight controller to be sent back to the receiver and then to the transmitter.
Redundancy Capabilities: SBUS supports redundancy setups, enabling multiple receivers to be linked. If one receiver loses signal, another can seamlessly take over, enhancing the reliability of the RC system.
FrSky has also developed SBUS-24, an extended version of the protocol that supports 24 channels, although this is only compatible with certain FrSky products. The standard SBUS protocol operates at 100,000 bits per second, providing a balance between speed and reliability suitable for most RC applications.
Overall, SBUS is valued for its simplicity, reliability, and ability to support advanced features like telemetry and redundancy, making it a preferred choice in the RC community.
What is FBUS and how does it differ from SBUS?
FBUS is FrSky's latest and most advanced serial data protocol, building on the foundation laid by SBUS and F.Port. FBUS combines control and telemetry data into a single line, supporting bidirectional communication. This means it can handle both the transmission of control signals and the reception of telemetry data from various sensors, servos, and ESCs (Electronic Speed Controllers) all through one connection. Unlike SBUS, which only allows for control data, FBUS can also receive detailed telemetry information such as current, voltage, temperature, and more. FBUS operates at a faster rate of 460,800 bits per second, significantly improving the speed and efficiency of data transmission compared to SBUS and F.Port.
Can I use SBUS and FBUS with the same equipment?
Yes, many modern FrSky receivers and flight controllers support both SBUS and FBUS. This compatibility allows users to choose the protocol that best suits their setup and requirements. However, it's essential to ensure that your specific equipment supports the desired protocol and that you configure it correctly. For instance, FrSky's Xact series brushless servos are compatible with both protocols, allowing for flexible and advanced setups.
What are the benefits of using FBUS over SBUS?
The primary benefits of using FBUS over SBUS include:
Enhanced Data Transmission Speed: FBUS operates at 460,800 bits per second, which is four times faster than SBUS.
Bidirectional Communication: FBUS supports both control and telemetry data on a single line, simplifying wiring and setup.
Advanced Telemetry Capabilities: FBUS can receive detailed telemetry data from compatible devices, providing more comprehensive monitoring and control.
Versatility: FBUS can be used with a variety of sensors, servos, and ESCs, making it a versatile choice for complex RC setups.
What kind of devices can I connect using FBUS?
FBUS is compatible with a wide range of devices, including:
Servos: Such as FrSky's Xact series, which support telemetry feedback for current, voltage, and temperature.
ESCs: That can send back telemetry data like temperature and current usage.
Telemetry Sensors: Including GPS, voltage, current, airspeed, and more, all connected on the same signal line.
If you have more questions about integrating SBUS or FBUS into your RC setup, feel free to contact us for expert advice and support.