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Brake

There is no friction brake

The kart has no mechanical brake. All braking is the ESC's electronic regenerative motor braking, commanded by software. A power or software failure removes braking authority — which is why the independent hardware e-stop exists.

How braking is commanded

The ESC exposes a low-brake line (a discrete input). The firmware drives it through a MOSFET as a held ground: the line is grounded (brake engaged) for as long as braking is wanted, and released otherwise.

  • Mainboard: Teensy pin 4 → ESC "Low Brake" (ESC pin 21), active-low.
  • It engages the ESC's highest regen level in one step, so it is a binary input, not a proportional one.

The pedal is a switch, not a proportional command

Because the ESC's brake input is one-step, the brake pedal (or the RC stick's lower band) is treated as a threshold switch:

flowchart LR
    pedal["Brake pedal / RC stick"] --> thr{"≥ 20% travel?"}
    thr -->|yes| on["Ground the ESC brake line<br/>(max regen)"]
    thr -->|no| off["Release the brake line"]
    on --> override["Brake ALWAYS overrides throttle"]
  • Past 20 % pedal travel the brake line is held; below it, released.
  • Brake always overrides throttle — while braking, the throttle DAC is forced to zero.
  • The brake line is also forced on during a controlled stop (the STOPPING state) regardless of the pedal.
  • Pressing the brake is also one leg of the wheel ARM chord.

On the RC remote, the same 20 % threshold applies to the lower band of the left stick — see the throttle glide band.

Proportional braking (future / research)

The SOFTWARE-STACK-PLAN.md describes a research track toward proportional braking — either by setting the ESC's regen level live over the FarDriver serial protocol, or by experimenting with a duty-cycled brake line. Neither is implemented today; braking is the one-step threshold switch described above.

Two brake lines on the ESC connector

The ESC connector exposes both a Low Brake (pin 21, active-low) and a High Brake (pin 11, active-high 12 V). The board drives Low Brake via the MOSFET on Teensy pin 4. See the Mainboard Pin Map.