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Step 06 — Replacing RMT with PWM

After this step the same portal command flow will drive a PWM output instead of RMT. A typical use case is a heater controlled via a MOSFET or a DC dimmer.

How it works

The executor is a plain callback function. RmtOutputAdapter from the previous step is one implementation. Replace it with ledcWrite code — everything else (MQTT, commands, status) stays unchanged.

Steps

1. Remove the RmtOutputAdapter include and instance from main.cpp:

// Remove:
#include "controller/RmtOutputAdapter.h"
static iheaterlink::RmtOutputAdapter s_output{iheaterlink::RmtOutputConfig{}};

2. Add PWM initialisation in setup():

#define PWM_PIN     0      // GPIO for MOSFET gate
#define PWM_CHANNEL 0      // LEDC channel (0–15)
#define PWM_FREQ_HZ 25000  // 25 kHz — inaudible for most heaters
#define PWM_RES     8      // 8-bit → duty 0–255

ledcSetup(PWM_CHANNEL, PWM_FREQ_HZ, PWM_RES);
ledcAttachPin(PWM_PIN, PWM_CHANNEL);
ledcWrite(PWM_CHANNEL, 0);  // off at startup

3. In the command handler replace s_output.apply(cmd) with ledcWrite:

device().onCommand("invoke", [](JsonObjectConst data) {
    const char* action   = data["action"] | "";
    JsonObjectConst args = data["args"];

    if (strcmp(action, "heat.start") == 0) {
        float power01 = args["power"] | 1.0f;  // 0.0–1.0
        uint8_t duty  = (uint8_t)(power01 * 255.0f);
        ledcWrite(PWM_CHANNEL, duty);

        device().status.mode[0]             = iDryer::UnitMode::Drying;
        device().telemetry.heaterPower01[0] = power01;
        device().publishStatusNow();

    } else if (strcmp(action, "heat.stop") == 0) {
        ledcWrite(PWM_CHANNEL, 0);

        device().status.mode[0]             = iDryer::UnitMode::Idle;
        device().telemetry.heaterPower01[0] = 0.0f;
        device().publishStatusNow();
    }
});

4. loop() does not change:

void loop() {
    device().loop();
}

Warning

ledcSetup / ledcAttachPin is the Arduino ESP32 API for versions before 3.x. In version 3.x and above use ledcAttach(pin, freq, resolution) and ledcWrite(pin, duty). Check your version in platformio.ini (platform = espressif32@X.Y.Z).

Verification

Press the Heat button on the portal. The output pin will carry a PWM signal with a duty cycle proportional to the power argument. Verify with a multimeter (average voltage) or an oscilloscope.

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