• MCU: ESP32-DEVKIT-V1
• Framework: Arduino
• Build system: PlatformIO
• Key libraries: built-in WiFi.h only

Ini
[env:esp32dev]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200
upload_speed = 921600
build_flags =
    -DCORE_DEBUG_LEVEL=3

Cpp
#include <Arduino.h>
#include <WiFi.h>

static constexpr int PIN_ADC_CURRENT = 34;   // U1:D34
static constexpr int PIN_ADC_VOLTAGE = 36;   // U1:VP
static constexpr int PIN_STATUS_LED  = 25;   // U1:D25
static constexpr int PIN_OPTO_OUT    = 26;   // U1:D26

static constexpr uint32_t SERIAL_BAUD = 115200;
static constexpr uint32_t SAMPLE_PERIOD_MS = 1000;
static constexpr uint8_t ADC_BITS = 12;
static constexpr float ADC_VREF = 3.3f;
static constexpr float ADC_MAX_COUNT = 4095.0f;
static constexpr float CT_BIAS_VOLTAGE = 1.65f;
static constexpr float ZMPT_DIVIDER_RATIO = (10.0f / (27.0f + 10.0f));

const char* WIFI_SSID = "YOUR_WIFI_SSID";
const char* WIFI_PASS = "YOUR_WIFI_PASSWORD";

unsigned long lastSampleMs = 0;
unsigned long lastWifiRetryMs = 0;

static float adcCountsToVoltage(int counts) {
    return (static_cast<float>(counts) * ADC_VREF) / ADC_MAX_COUNT;
}

static float readCurrentChannelVoltage(void) {
    int raw = analogRead(PIN_ADC_CURRENT);
    float voltage = adcCountsToVoltage(raw);
    return voltage - CT_BIAS_VOLTAGE;
}

static float readVoltageChannelAtAdc(void) {
    int raw = analogRead(PIN_ADC_VOLTAGE);
    return adcCountsToVoltage(raw);
}

static float estimateZmptModuleOutput(float adcVoltage) {
    return adcVoltage / ZMPT_DIVIDER_RATIO;
}

static void setOptoOutput(bool enabled) {
    digitalWrite(PIN_OPTO_OUT, enabled ? HIGH : LOW);
}

static void initWifi(void) {
    WiFi.mode(WIFI_STA);
    WiFi.begin(WIFI_SSID, WIFI_PASS);

    unsigned long startMs = millis();
    while (WiFi.status() != WL_CONNECTED && (millis() - startMs) < 10000UL) {
        delay(250);
        Serial.print('.');
    }
    Serial.println();

    if (WiFi.status() == WL_CONNECTED) {
        Serial.print("WiFi connected, IP: ");
        Serial.println(WiFi.localIP());
    } else {
        Serial.println("WiFi not connected; continuing in offline logging mode.");
    }
}

void setup() {
    Serial.begin(SERIAL_BAUD);
    delay(200);
    Serial.println("ESP32 energy monitor starting...");

    pinMode(PIN_STATUS_LED, OUTPUT);
    pinMode(PIN_OPTO_OUT, OUTPUT);

    digitalWrite(PIN_STATUS_LED, LOW);
    digitalWrite(PIN_OPTO_OUT, LOW);

    analogReadResolution(ADC_BITS);
    analogSetPinAttenuation(PIN_ADC_CURRENT, ADC_11db);
    analogSetPinAttenuation(PIN_ADC_VOLTAGE, ADC_11db);

    initWifi();
}

void loop() {
    unsigned long now = millis();

    if (WiFi.status() != WL_CONNECTED && (now - lastWifiRetryMs) >= 30000UL) {
        lastWifiRetryMs = now;
        Serial.println("Retrying WiFi connection...");
        WiFi.disconnect(true, true);
        delay(100);
        initWifi();
    }

    if ((now - lastSampleMs) >= SAMPLE_PERIOD_MS) {
        lastSampleMs = now;

        float ctAcComponent = readCurrentChannelVoltage();
        float adcVoltage = readVoltageChannelAtAdc();
        float zmptModuleOutput = estimateZmptModuleOutput(adcVoltage);

        Serial.print("CT centered voltage (V): ");
        Serial.print(ctAcComponent, 4);
        Serial.print(" | Voltage ADC (V): ");
        Serial.print(adcVoltage, 4);
        Serial.print(" | Estimated ZMPT OUT (V): ");
        Serial.println(zmptModuleOutput, 4);

        bool telemetryActive = (WiFi.status() == WL_CONNECTED);
        digitalWrite(PIN_STATUS_LED, telemetryActive ? HIGH : !digitalRead(PIN_STATUS_LED));
        setOptoOutput(telemetryActive);
    }
}

• Build: pio run
• Flash: pio run -t upload
• Serial monitor: pio device monitor -b 115200
• Normal reset: press the external SW1 reset button tied to EN
• Bootloader entry: use the board's built-in BOOT mechanism if your DevKit exposes it; this schematic currently adds only external reset, not an external GPIO0 boot button

• GPIO34 and GPIO36/VP are ADC1 inputs, so they remain usable while WiFi is active.
• The CT channel is biased at midscale and should be calibrated in firmware for offset and scaling after hardware bring-up.
• The ZMPT101B module output is additionally divided by R5/R6 before the ESP32 ADC; calibrate the final mains-voltage conversion in software.
• GPIO26 drives the PC817 LED through R9; set it HIGH to energize the optocoupler.