Distance sensors#

A VL53L0X on any sensor port gives you range in millimetres.

Reading distance#

double mm = exp.getDistanceMm(1);

The board detects the sensor type by itself, so there is nothing to configure. Asking for a distance from a port holding a colour sensor throws rather than returning nonsense.

Invalid readings#

A distance sensor cannot always produce an answer. Nothing in range, a surface too dark to bounce enough light back, bright sunlight washing out the return — all of these give you a reading that means “I don’t know” rather than a distance.

Check validity before trusting a number:

BBRDigitalExpander.TelemetryBlock t = exp.readTelemetry();
if (t.isDistanceValid(1)) {
    double mm = t.distanceMm[1];
}

The telemetry block also carries signalRate and ambientRate, which tell you why a reading is weak — low signal means not enough light coming back, high ambient means too much light overall.

Triggering on proximity#

The board can watch the distance for you and drive a digital output when something comes within range:

exp.triggerWhenNear(0, 1, 300);   // output 0 high when port 1 sees something within 300 mm

Saved automatically. Your match code reads a DigitalChannel and does no I2C at all.

This helper sets a signal-rate floor for you, so weak edge-of-range returns don’t cause the output to chatter. That is exactly the kind of tuning value the everyday tier exists to hide.

Full control#

If you need a two-sided window — “between 100 mm and 300 mm” rather than “closer than 300 mm” — use the advanced tier:

BBRDigitalExpander.DistanceClass cls = new BBRDigitalExpander.DistanceClass();
cls.distMin = 100;
cls.distMax = 300;
cls.hysteresisMm = 10;      // stops chatter at the boundary
cls.minSignalRate = 100;    // reject weak returns
exp.writeDistanceClass(1, 5, cls);   // port 1, class slot 5
exp.saveConfigToFlash();             // advanced tier does NOT auto-save

hysteresisMm is what stops the output flickering when the robot sits exactly on the threshold. Leave it at the default unless you have a reason.

Worked example#

BBRDistanceTriggerSetup is the canonical setup-once OpMode, and BBRDistanceTriggerRuntime is the match half that reads a plain digital input. See Example OpModes.