Step 3: Scaffold the firmware

Create an ESP-IDF C++ project:

idf.py create-project device
cd device

Add the RelayX Device SDK for C++ to device/main/idf_component.yml:

dependencies:
  relay/device-cpp: "^0.3.0"
  idf: ">=5.0"

Create device/main/app_shared.h. This header holds the config constants and shared globals used across the tutorial:

#pragma once

#include <atomic>
#include <cstdint>
#include "freertos/FreeRTOS.h"
#include "freertos/event_groups.h"
#include "driver/gpio.h"
#include "relay/device.h"

#define WIFI_SSID          ""
#define WIFI_PASS          ""

#define I2C_SDA_GPIO       GPIO_NUM_21
#define I2C_SCL_GPIO       GPIO_NUM_22
#define INA219_I2C_ADDR    0x40

#define RELAY_GPIO         GPIO_NUM_26
#define RELAY_ACTIVE_HIGH  0

#define RPC_SET_STATE      "state"
#define RPC_UPDATE_RATE    "updateSampleRate"

#define TELEMETRY_POWER    "power"
#define TELEMETRY_CURRENT  "current"
#define TELEMETRY_VOLT     "volt"

constexpr uint32_t SAMPLE_RATE_MIN_MS     = 100;
constexpr uint32_t SAMPLE_RATE_MAX_MS     = 600000;
constexpr uint32_t SAMPLE_RATE_DEFAULT_MS = 10000;

extern std::atomic<uint32_t> g_sample_rate_ms;
extern RelayDevice *g_device;
extern EventGroupHandle_t g_state_events;

constexpr EventBits_t DEVICE_READY_BIT = BIT0;

extern const relay_device_config_t device_config;

Fill in your WiFi credentials. The RelayX credentials are defined in the next step, inside app_shared.cpp.