gweimer/hc-sr04-ultrasonic/ultrasonic-range

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ultrasonic-range

@/ultrasonic-range

TRIGnumber

Board port to which sensor’s `trig` pin is connected.

ECHOnumber

Board port to which sensor’s `echo` pin is connected.

PINGpulse

Triggers new ultrasonic ping which would result in the output update once sound echo will be captured. Pulses coming within 60 ms window after last one are ignored to fight sensor’s PCB resonance.

Dmnumber

Last measured distance in meters.

To use the node in your project you should have the gweimer/hc-sr04-ultrasonic library installed. Use the “File → Add Library” menu item in XOD IDE if you don’t have it yet. See Using libraries for more info.

struct State {
    TimeMs cooldownUntil = 0;
};

{{ GENERATED_CODE }}

static const uint32_t HCSR04_COOLDOWN_MS = 60;
static const uint32_t HCSR04_MAX_START_US = 5000;
static const uint32_t HCSR04_MAX_ROUNDTRIP_US =
    1000ul * 1000ul         // seconds to μs
    * 4ul                   // max meters
    * 2ul                   // to the moon and back
    / 340ul;                // sound speed

enum Status {
    HCSR04_OK,
    HCSR04_NO_ECHO,
    HCSR04_WRONG_CONNECTION
};

Status pingSync(uint8_t echoPort, uint8_t trigPort, uint32_t* outRoundtripUs) {
    uint32_t maxUs;

    // Request measurement: make a pulse for 10 μs.
    pinMode(trigPort, OUTPUT);
    digitalWrite(trigPort, HIGH);
    delayMicroseconds(10);
    digitalWrite(trigPort, LOW);

    // Wait for echo pin rise which means ultrasonic burst success
    maxUs = micros() + HCSR04_MAX_ROUNDTRIP_US;
    pinMode(echoPort, INPUT);
    while (digitalRead(echoPort) == LOW) {
        if (micros() > maxUs) {
            *outRoundtripUs = HCSR04_MAX_ROUNDTRIP_US;
            return HCSR04_OK;
            //return HCSR04_WRONG_CONNECTION;
        }
    }

    // Now wait for echo line to be pulled back low which means echo capture
    uint32_t tStart = micros();
    maxUs = tStart + HCSR04_MAX_ROUNDTRIP_US;
    while (digitalRead(echoPort) == HIGH) {
        if (micros() > maxUs) {
            *outRoundtripUs = -HCSR04_MAX_ROUNDTRIP_US;
            return HCSR04_OK;
            //return HCSR04_NO_ECHO;
        }
    }

    *outRoundtripUs = micros() - tStart;
    return HCSR04_OK;
}

void evaluate(Context ctx) {
    if (!isInputDirty<input_PING>(ctx))
        return;

    auto state = getState(ctx);
    if (millis() < state->cooldownUntil) {
        emitValue<output_Dm>(ctx, -1);
        return;
    }

    auto echoPort = (uint8_t)getValue<input_ECHO>(ctx);
    auto trigPort = (uint8_t)getValue<input_TRIG>(ctx);

    uint32_t t;
    auto status = pingSync(
        (uint8_t)getValue<input_ECHO>(ctx),
        (uint8_t)getValue<input_TRIG>(ctx),
        &t
    );

    // We should not ping too often as the PCB of the sensor could resonate
    state->cooldownUntil = millis() + HCSR04_COOLDOWN_MS;

    if (status == HCSR04_OK)
        emitValue<output_Dm>(ctx, Number(t) / 1000000.0 * 170);
}

ultrasonic-range

gweimer/hc-sr04-ultrasonic/ultrasonic-range

C++ implementation