flowchart LR FC[Flight controller] -->|DShot| ESC[ESC] ESC -->|3-phase| M[Brushless motor] M --> P[Prop -> thrust] M -. back-EMF .-> ESC ESC -. telemetry .-> FC
Brushless Motors, ESCs, and ESC Firmware for a Drone Build
How brushless motors, electronic speed controllers, and their firmware fit together on a drone - motor types, DShot vs PWM, and where thrust actually comes from.
A drone is four fast control loops turning digital throttle into torque. The chain is flight controller -> ESC -> brushless motor -> prop, and the interesting engineering is in the ESC and its firmware. From the Hardware_Tools repo: motors, ESC, ESC firmware, and the drone build.
Motor types, and why drones use brushless
| Type | Commutation | Efficiency | Control | Drone use |
|---|---|---|---|---|
| Brushed | Mechanical brushes | Low | Simple (voltage) | Toys only |
| Brushless (BLDC) | Electronic (ESC) | High | Needs an ESC | Yes - the standard |
| Servo | Position feedback | n/a | PWM angle | Gimbals, not props |
| Stepper | Step sequencing | Med | Open-loop steps | CNC, not drones |
Brushless wins: no brushes to wear, high power-to-weight, and precise electronic commutation - at the cost of needing an ESC to do that commutation. Background: Electric Motors.
The signal chain
The ESC reads a throttle command, energises the three phases in sequence, and senses back-EMF to know rotor position. Firmware is what makes that smooth and fast.
ESC firmware
| Firmware | Protocols | Notes |
|---|---|---|
| BLHeli_S | DShot up to 600 | Common, closed, hardware-specific |
| BLHeli_32 | DShot 1200, telemetry | 32-bit, feature-rich (now sunset) |
| AM32 | DShot, telemetry | Open-source, active, the modern pick |
Digital protocols (DShot) beat analog PWM: no calibration, checksummed frames, and bidirectional telemetry (RPM back to the FC). See ESC firmware.
Why DShot over PWM
Analog PWM needs endpoint calibration and drifts; DShot sends a checksummed digital value. Update rates and integrity both jump.
Where thrust comes from
Thrust rises roughly with the square of prop RPM, so the top of the throttle range buys the most thrust - and draws the most current. Motor KV, prop pitch, and cell count set where you sit on this curve. More in Brushless Motors.
Takeaway
Pick a brushless motor for its KV to match your cells and prop, run open AM32 firmware, and drive it with DShot for a clean digital loop with RPM telemetry. Full build notes: Drone Build.