Recipe 7 — Oscilloscope-Style Centered View¶

An oscilloscope-style view needs a stable time window, predictable sample timing, and reference lines that make the input range easy to read. This recipe configures a single time-domain plot in microseconds with visible ground and mid-rail references.

Zero-centered scope view with volts on Y — Recipe 7 — zero-centered scope view with V on Y

#include <ViewPoint.h>
using namespace viewpoint;

const float VREF = 3.3f;
const uint32_t SAMPLE_RATE = 10000; // 10 kSPS
const int DISPLAY_SAMPLES = 500;
const uint32_t SAMPLE_INTERVAL_US = 1000000UL / SAMPLE_RATE;

uint32_t lastSampleUs = 0;

void setup() {
    view.begin();
    view.setDelay(0);
    view.setTitle("Oscilloscope");

    float time_span_us = DISPLAY_SAMPLES * (1.0f / SAMPLE_RATE) * 1e6f;
    float half_span = time_span_us / 2.0f;

    view.setPlotTitle("Oscilloscope");
    view.setVerticalRange(-0.5, 3.5, 8);
    view.setHorizontalRange(-half_span, half_span, 10);
    view.setAxisLabels("Time", "Voltage");
    view.setUnits("us", "V");
    view.addHorizontalReferenceLine(VREF / 2.0f, colors::DimGray);
    view.addHorizontalReferenceLine(0.0f, colors::DimGray);
}

void loop() {
    uint32_t now = micros();
    if (now - lastSampleUs < SAMPLE_INTERVAL_US) return;
    lastSampleUs += SAMPLE_INTERVAL_US;

    float volts = analogRead(A0) * VREF / 1023.0f;
    view.addData("Probe", volts);
    view.send();
}

What the functions do

setDelay(0) disables the library's built-in delay so the micros() gate controls sample cadence.
setHorizontalRange(-half_span, half_span, 10) gives the time-domain view a stable left/right span around zero.
setVerticalRange(-0.5, 3.5, 8) frames a 0–3.3 V ADC signal with headroom above and below the rails.
Reference lines at VREF / 2.0f and 0.0f mark mid-rail and ground, common scope landmarks for single-supply signals.