Understanding MultiShot: Upgraded ESC Protocol from OneShot125

RaceFlight represents the cutting edge in flight controller firmware in 2016, leveraging the advanced processing capabilities of F4 flight controllers to achieve looptimes as low as 125us. Alongside, we’ll explore MultiShot—an ESC protocol that drastically outpaces its predecessors like Oneshot125 and traditional PWM, being up to 80 times faster!

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For newcomers to open source 32-bit flight controller and ESC firmware, the following resources could be helpful:

• What is F1, F3, F4, F7 and H7 Flight Controller
• Understanding Betaflight Firmware
• A Comprehensive List of ESC Protocols
• Cleanflight vs. Baseflight

What is Raceflight?

RaceFlight, initiated by RS2K from RCGroups, is a branch derived from Betaflight, modified specifically for F4 flight controller targets. It aims to push beyond the current capabilities of F1 and F3 flight controllers, which are already maximized by Betaflight.

Baseflight > Cleanflight > Betaflight > Raceflight

The GUI for RaceFlight is based on a modified version of the Cleanflight configurator, facilitating firmware flashing and setting adjustments via a Chrome app. The integration of RaceFlight features into Cleanflight is anticipated, potentially optimizing the utilization of next-gen hardware.

Though setting up RaceFlight may initially seem more complex than Cleanflight or Betaflight, the process becomes straightforward once configured.

What is Multishot?

Multishot stands out as the fastest PWM signal protocol available, significantly reducing signal times to between 5 and 25 microseconds—making it about ten times faster than OneShot125, which itself is eight times quicker than standard PWM. Developed by Flyduino, Multishot’s speed allows for unprecedented responsiveness and precision in flight control.

Despite newer protocols like OneShot42 (three times faster than OneShot125) entering the scene, Multishot remains superior in speed. However, compatibility is crucial; initial tests indicate that newer generation ESCs, particularly those with Silabs F390 chips like the DYS XM20A, are better suited for Multishot compared to older models like the Littlebee 20A with Silabs F330.

Before attempting to use Multishot, thorough compatibility checks are essential to prevent hardware issues or damage. The excitement around technologies like DYS XM20A underscores the community’s eagerness to adopt these advanced protocols, despite the risks involved with older hardware.

The Advantages of Lower Looptime and Faster ESC Protocols

A common question in the drone community is the true value of pursuing ever-lower looptimes and faster ESC protocols. To many, these enhancements seem superfluous, given human limitations in reaction speed. Critics argue that the relentless drive toward lower looptimes yields diminishing returns, diverting attention from more practical performance improvements.

However, from my perspective, the benefits of reduced system latency are substantial. Our flight controllers and algorithms continuously predict future states based on sensor data. This prediction relies heavily on precise tuning—specifically, the settings of PID values and filters. Often, we find ourselves bogged down in tuning details, potentially losing sight of the sheer joy of flying.

Theoretically, a system with minimized delay allows the quadcopter to respond more proactively based on current sensor readings, thereby reducing the dependency on PIDs for a well-performing multicopter.

Moreover, there’s another critical aspect to consider: control delay. When flying, especially for those of us using FPV gear, every millisecond counts when avoiding obstacles like trees. The delay from input command to quadcopter response includes latency from the FPV system, the radio transmission, and the drone’s internal processing.

By reducing these delays, we enhance our control over the drone, allowing for more precise and safer maneuvering. This is why I believe that any reduction in system lag is not just beneficial but essential for improving our interaction with these complex flying machines.

Development of Raceflight and Multishot

Raceflight initially catered exclusively to F4 flight controllers but has since broadened its compatibility to include F1 and F3 targets. Here’s a current list of supported flight controllers as of the latest update, RC7:

• Afro Mini F1
• AlienFlightF4
• AlienWii F1/F3
• BlueJayF4
• CC3D F1
• Colibri – TBS Powercube F3
• Naze32 F1
• Motolab Tornado F3
• Revo F4
• Revo Nano F4
• RMRC Dodo F3
• Sparky2 F4
• SPRacing F3
• VRCore F4 (this is as of RC7, other targets available in previous releases)

Additional models supported in earlier releases add to the versatility of Raceflight. The development team, including notable figures like Dominic and Boris alongside the broader open source community, continues to refine and enhance the firmware, promising significant improvements in flight control.

Revo F4

There’s even discussion around integrating two-way communication between the flight controller and the ESC, among other advancements envisioned by RS2K, the project lead for Raceflight.

Choosing Between Raceflight, Cleanflight, and Betaflight

Deciding whether to use Raceflight over alternatives like Cleanflight or Betaflight often boils down to personal preference and the specific hardware in use. What may work for others might not suit your setup, and part of the excitement in this hobby lies in experimenting with different technologies to see what best enhances your flying experience.

If you’ve explored Raceflight and have insights or experiences to share, I encourage you to contribute to the community discussion. Your feedback not only helps others make informed decisions but also supports the continuous improvement of these technologies.

Lastly, if you find value in the enhancements brought about by these open source projects and appreciate how they elevate your multirotor’s performance, consider showing your gratitude through donations. Every contribution helps sustain the developers’ efforts, enabling them to continue their work and innovation for the benefit of all enthusiasts.