xod/common-hardware/hc-sr04-ultrasonic-time

Measures sound roundtrip time with HC-SR04 ultrasonic range meter. Outputs infinity on no echo. Possible errors: — Invalid port — Wrong connection

hc-sr04-ultrasonic-time

@/hc-sr04-ultrasonic-time

Deprecated: Use nodes from the `xod-dev/hc-sr04` standard library instead.

Measures sound roundtrip time with HC-SR04 ultrasonic range meter. Outputs infinity on no echo. Possible errors: — Invalid port — Wrong connection

TRIGport

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

ECHOport

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.

DONEpulse

Fires when ping is done

Tsnumber

Last measured sound roundtrip time in seconds.

#pragma XOD evaluate_on_pin disable
#pragma XOD evaluate_on_pin enable input_PING

struct State {
    TimeMs cooldownUntil = 0;
};

{{ GENERATED_CODE }}

constexpr uint32_t HCSR04_COOLDOWN_MS = 60;
constexpr uint32_t HCSR04_MAX_START_US = 5000;
constexpr 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_START_US;
    pinMode(echoPort, INPUT);
    while (digitalRead(echoPort) == LOW) {
        if (micros() > maxUs)
            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)
            return HCSR04_NO_ECHO;
    }

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

void evaluate(Context ctx) {
    static_assert(isValidDigitalPort(constant_input_ECHO), "must be a valid digital port");
    static_assert(isValidDigitalPort(constant_input_TRIG), "must be a valid digital port");

    if (!isInputDirty<input_PING>(ctx))
        return;

    auto state = getState(ctx);
    if (millis() < state->cooldownUntil)
        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_Ts>(ctx, Number(t) / 1000000.0);
        emitValue<output_DONE>(ctx, 1);
    } else if (status == HCSR04_NO_ECHO) {
        emitValue<output_Ts>(ctx, INFINITY);
        emitValue<output_DONE>(ctx, 1);
    } else {
        raiseError(ctx); // HCSR04_WRONG_CONNECTION
    }
}

hc-sr04-ultrasonic-time

xod/common-hardware/hc-sr04-ultrasonic-time

C++ implementation