BLHeli_S, Bluejay and AM32 ESC firmware compared for FPV drones: 8-bit vs 32-bit, RPM filter and which one to pick for your ESC.
ESC firmware is the code that decides how each motor answers the flight controller. Plenty of pilots assume they need to buy a new ESC to gain performance, when in practice reflashing the one they already own is often enough. Here is the catch: the names BLHeli_S, Bluejay and AM32 get thrown around as if they were three interchangeable options, and they are not. Two of them run on 8-bit hardware and the third needs 32-bit hardware. Understanding that split decides most of the comparison for you.
The most important divide is not between firmwares but between hardware generations. BLHeli_S and Bluejay run on 8-bit microcontrollers, the ones found on most budget and mid-range ESCs of the last few years. AM32 needs a more capable 32-bit microcontroller, present on newer ESCs. You cannot install AM32 on an 8-bit board no matter how much you want to: the chip will not run it. That is why the first step is always to identify your ESC. Check the manufacturer model or the product listing: if it says BLHeli_S, it is 8-bit and your path is Bluejay. If the ESC is advertised as 32-bit or AM32-ready, then AM32 is a real option.
The RPM filter is the tangible upgrade that separates Bluejay and AM32 from old BLHeli_S. The motor reports its real revolutions back to the flight controller over bidirectional DShot, and BetaFlight uses that data to precisely filter vibration noise out of the gyro signal. The result is cleaner flight, cooler motors, and room to lower the remaining filters, which cuts latency. BLHeli_S has no native RPM filter. Bluejay adds it on the same 8-bit hardware and also unlocks a 48 kHz switching mode for smoother control. AM32 ships with it as standard in the 32-bit world. If you are coming from BLHeli_S with no RPM filter, this is the main reason to upgrade.
Do not choose on marketing, choose on the chip. 8-bit ESC: flash Bluejay. It is free, flashes from BLHeli Configurator or equivalent tools, keeps your hardware, and gives you the RPM filter and 48 kHz. There is no practical reason to leave BLHeli_S on an ESC that can run Bluejay. 32-bit ESC: flash AM32. It is open source, actively developed, recommended by BetaFlight, and it makes use of the 32-bit microcontroller. What you cannot do is cross the paths: AM32 will not boot on 8-bit and Bluejay adds nothing to an ESC built for 32-bit. Check your ESC first and the decision makes itself.
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