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Frequency Input » History » Revision 1

Revision 1/2 | Next »
Adam Klama, 06/21/2026 02:23 PM

Frequency Input# Frequency Input

Overview

A Frequency Input reads a pulsing signal on a hardware pin and, depending on
its mode, reports the signal's:

  • Frequency — pulses per second;
  • Speed / RPM — frequency scaled by the tooth count of the wheel/sensor;
  • Duty — the on/off ratio of the signal;
  • Time — the pulse/period time.

Use it for crank/shaft speed sensors (including missing-tooth wheels), wheel-speed
sensors, flow meters, and any frequency- or duty-output sensor.

This input also covers what older configs called the separate Frequency and
Duty inputs — they are folded in here as modes.

Prerequisites & hardware

  • A sensor that produces a pulse train on the pin (Hall, VR via a conditioner,
    optical, etc.), wired to the pin with a common ground.
  • For speed/RPM, know the tooth count (pulses per revolution).
  • Pull-up support is hardware dependent — only some pins provide it. Where it
    is absent, condition the signal externally.

Add it in the app

  1. Add a new input and choose Frequency Input as the type.
  2. Select the pin and give it a clear alias (e.g. Crank Speed).
  3. Choose the mode (Frequency, Duty or Time) and, for speed, set the
    tooth count.
  4. Set the signal mode and detection threshold voltages to match the sensor.

Settings reference

Schema: config/PhonicWheelConfiguration.proto.

Setting Meaning Unit Range / values Notes
Mode What the input reports — Frequency, Duty, Time Frequency (with tooth count) gives speed/RPM; Duty = on/off ratio; Time = pulse/period time.
Tooth count Pulses per revolution teeth uint32 Scales frequency into speed/RPM.
Missing tooth count Number of missing teeth on the wheel teeth uint32 For missing-tooth crank wheels (e.g. 60-2 → 2). 0 for an even wheel.
Signal mode How the pulse edges are interpreted — Legacy, Positive pulse, Negative pulse, Quadrature, Quadrature rising edge, Quadrature falling edge Quadrature modes use a two-channel sensor and give direction; pulse modes count single-channel edges.
Median filter length Median filter window samples int Rejects spikes; larger = smoother but slower to respond.
Pull mode Direction of the input pull — Up, Down Sets the idle level for the detection comparator.
Enable pull-ups Enable the pin pull-up(s) — on / off Hardware dependent — only on pins that provide a pull-up.
Pull-up voltage Adjustable pull-up reference mV uint32 The pull-up rail used by the detection thresholds (adjustable-pull-up hardware).
Reference voltage / Hi / Lo Detection comparator thresholds mV uint32 The switching thresholds that turn the analog signal into clean pulses (with hysteresis between Hi and Lo).
Fault voltage Hi / Lo Fault thresholds mV uint32 Readings beyond these flag an open/short or failed sensor.
Input config Whether to (re)configure the pin hardware — Configure, Skip configuration Skip configuration leaves the pin hardware as-is (advanced).

Common settings

Frequency Input also uses the shared settings — alias and pin. See
Common IO Settings.

Example — crank speed from a 60-2 wheel

  1. Type Frequency Input, alias Crank Speed, on the sensor's pin.
  2. Mode Frequency, Tooth count 60, Missing tooth count 2.
  3. Signal mode Positive pulse (single-channel Hall).
  4. Set Reference Hi/Lo thresholds with enough hysteresis to reject noise.
  5. Median filter length a few samples to suppress spikes at speed.

Troubleshooting

  • No reading / drops out at speed: check the threshold voltages and add
    median filtering; verify the sensor type matches the signal mode.
  • Speed/RPM reads wrong by a factor: the tooth count (or missing-tooth
    count) doesn't match the wheel.
  • Counts in the wrong direction: use a Quadrature signal mode with a
    two-channel sensor.
  • Reads a fault: the level is beyond Fault voltage Hi/Lo — check wiring.

Related

Updated by Adam Klama 1 day ago · 2 revisions