What Is Bluejay ESC Firmware?
Bluejay is a free, open-source firmware that upgrades BLHeli_S electronic speed controllers (ESCs) with features previously reserved for more expensive hardware. If you're running BLHeli_S ESCs and want bidirectional DShot support for RPM filtering without buying new hardware, Bluejay is worth a look.
Bluejay vs BLHeli_S: The Key Differences
BLHeli_S is solid, reliable firmware found on countless budget and mid-range ESCs. It handles the basics well, but lacks one major feature: bidirectional DShot telemetry.
Bluejay changes that. It adds:
- Bidirectional DShot — Your ESC can talk back to the flight controller, sending real-time RPM data over the same wire used for control signals
- RPM filtering compatibility — Betaflight can use that RPM data to tune notch filters precisely, cutting motor noise without the latency of broader filters
- Adjustable PWM frequencies — Choose 24kHz, 48kHz, or 96kHz to balance efficiency and motor braking for your specific build
- Custom startup melodies — Personalise the tones your quad plays when you plug in a battery
- Better efficiency — Higher PWM frequencies can improve flight times, particularly on micro drones
Bluejay vs BLHeli_32
BLHeli_32 ESCs are the premium option, with 32-bit processors and native bidirectional DShot support. They're excellent, but they cost more.
Bluejay bridges the gap. Your 8-bit BLHeli_S hardware gains the headline feature — RPM filtering — without spending a penny on new components. You won't get every BLHeli_32 feature, but for most FPV pilots, RPM filtering is the one that matters.
The tradeoff? BLHeli_32 supports higher DShot rates and has more processing headroom. If you're building a high-end racing rig, BLHeli_32 remains the better choice. For freestyle, long-range, and general flying, Bluejay on BLHeli_S hardware offers excellent value.
Why RPM Filtering Matters
RPM filtering lets your flight controller place notch filters at the exact frequencies your motors generate. Instead of blanket filtering that adds delay, the filters track motor RPM in real time.
The result is smoother flights, cooler motors, and better tolerance for bent props. Many pilots report cleaner throttle response and reduced prop wash after enabling RPM filtering.
RPM filtering requires both bidirectional DShot support on the ESC and a compatible flight controller firmware. Betaflight 4.1 and later support it out of the box.
How to Flash Bluejay
Flashing Bluejay is straightforward using the ESC Configurator web app. You'll need:
- A Chrome-based browser
- Your drone connected via USB with battery power applied
- BLHeli_S compatible ESCs
Connect to your flight controller's serial port, detect your ESCs, select Bluejay from the firmware list, choose your PWM frequency, and flash. The whole process takes a few minutes.
PWM Frequency Guide
- 24kHz — Best for 5" freestyle and racing quads where motor braking matters
- 48kHz — A good middle ground for 3" to 5" builds
- 96kHz — Ideal for tiny whoops and micro drones, prioritising efficiency over braking
Which Products Support Bluejay?
Many modern flight controllers and ESCs ship with Bluejay pre-installed or explicitly support it. At Unmanned Tech, look for products tagged with "bluejay" or listed as BLHeli_S compatible.
Popular options include:
- SpeedyBee F405 AIO 40A — Ships with Bluejay firmware, 25.5mm mounting
- Axisflying Argus ECO Stack — F405 flight controller with 60A ESC running Bluejay_QH30
- Tmotor Velox V45A Lite V2 — BLHeli_S by default, Bluejay compatible
- HGLRC Specter F411 — Pre-flashed with Bluejay for micro builds
When Should You Use Bluejay?
If your current ESCs run BLHeli_S and you're not using RPM filtering, flashing Bluejay is one of the best free upgrades available. The performance gains are real, particularly if you fly freestyle or cinematic footage where smooth footage matters.
Skip Bluejay if you already run BLHeli_32 hardware with bidirectional DShot enabled, or if your flying style doesn't benefit from ultra-low filtering delay. Some very old or unusual BLHeli_S layouts may not have Bluejay support, though most common targets do.
Final Thoughts
Bluejay has become the go-to firmware for BLHeli_S ESCs because it delivers meaningful performance improvements at zero cost. If you're not using RPM filtering yet, it's worth the few minutes required to flash and configure.
Combine Bluejay with proper tuning in Betaflight and you'll notice the difference — cooler motors, cleaner flights, and a more locked-in feel through corners.