Implementing the Smart Home Control project

The STM32 instances come with support for Platform IO Core (CLI). We will be using it for working on our projects. To know more about Platform IO Core (CLI) and the different commands go to the Platform IO documentation.

First, we need to initialise a new project using Platform IO. Let's create a new folder called Smart-Home which will hold all our code related to the project and then open the newly created folder in the terminal. Use the following commands:

mkdir /workspace/Smart-Home/
cd /workspace/Smart-Home/

Now we will initialise a new project using Platform IO. Type the following command in the terminal:

pio project init --board nucleo_f411re

The pio project init command is used to initialise the project. Then we need to specify the board which we want to use with the --board flag.

Once the project init command has run successfully, we will see some new folders inside the Smart-Home folder. We will store the files related to the project in the src folder.

After running the project init command, if you can't see the new files, you may have to reload the project files by clicking on PROJECT in the File Explorer pane.

Create a new file called main.cpp inside the src folder. This file will hold the code for the Smart Home Control program. Click on the main.cpp file to open it up in our code editor. Now, paste the following code inside the main.cpp file.

#include <Arduino.h>

#include "Adafruit_MQTT.h"
#include "Adafruit_MQTT_Client.h"

#include <Ethernet.h>
#include <EthernetClient.h>

#include <Wire.h>

/************************* Ethernet Client Setup *****************************/
byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
IPAddress ip(172, 17, 0, 2);
IPAddress myDns(8, 8, 8, 8);

/************************* Setup *********************************/

#define AIO_SERVER      ""
#define AIO_SERVERPORT  1883
#define AIO_USERNAME  "yourusername"       //Replace this with your username
#define AIO_KEY       "youradafruitiokey"  //Replace this with your Adafruit IO key

/************ Global State (you don't need to change this!) ******************/

//Set up the ethernet client
EthernetClient client;


// You don't need to change anything below this line!
#define halt(s) { Serial.println(F( s )); while(1);  }

/****************************** Feeds ***************************************/

// Notice MQTT paths for AIO follow the form: <username>/feeds/<feedname>
Adafruit_MQTT_Publish light = Adafruit_MQTT_Publish(&mqtt,  AIO_USERNAME "/feeds/light");
Adafruit_MQTT_Subscribe lamp = Adafruit_MQTT_Subscribe(&mqtt, AIO_USERNAME "/feeds/lamp");

/************************* APDS Driver code *********************************/

class APDS9301 {
  bool begin(int addr = 0x29) {
    i2cAddr = addr;
    if (!setPower(true)) {
      return false;
    if (!setTiming(true, 0)) {
      return false;
    return true;

  bool setPower(bool on) {
    byte regVal = (on ? REG_CONTROL_POWER_ON : 0);

    return setReg(REG_CONTROL, regVal);

  bool setTiming(bool highGain, int integration) {
    byte regVal;

    if (highGain) {
      regVal = REG_TIMING_GAIN_16;
      gain = 1;
    else {
      regVal = REG_TIMING_GAIN_1;
      gain = 1 / 16.0;
    switch (integration) {
    case 0:
      regVal |= REG_TIMING_INTEGRATE_13_7MS;
      this->integration = TIMING_SCALE_13_7MS;
    case 1:
      regVal |= REG_TIMING_INTEGRATE_101MS;
      this->integration = TIMING_SCALE_101MS;
      regVal |= REG_TIMING_INTEGRATE_402MS;
      this->integration = TIMING_SCALE_402MS;
    return setReg(REG_TIMING, regVal);

  bool readLux(float *lux) {
    uint16_t ch0, ch1;
    if (!getReg16(REG_DATA0LOW, &ch0) || !getReg16(REG_DATA1LOW, &ch1)) {
      return false;
    *lux = calcLux(ch0, ch1);
    return true;

  bool setReg(int reg, byte val) {
    int size = Wire.write(reg | REG_COMMAND_CMD);
    if (size == 1) {
    if ((Wire.endTransmission() != 0) || (size != 1)) {
      return false;
    return true;

  bool getReg16(int reg, uint16_t *val) {
    int size = Wire.write(reg | REG_COMMAND_CMD | REG_COMMAND_WORD);
    if ((Wire.endTransmission() != 0) || (size != 1)) {
      return false;
    if (Wire.requestFrom(i2cAddr, 2) != 2) {
      return false;
    byte lsb =;
    *val =;
    *val = (*val << 8) | lsb;
    return true;

  float calcLux(uint16_t ch0, uint16_t ch1) {
    float ch0f = ch0 / gain / integration;
    float ch1f = ch1 / gain / integration;

    if (ch0f == 0) {
      return 0;
    float d = ch1f / ch0f;
    if (d <= 0.5) {
      return (0.0304 * ch0f - 0.062 * ch0f * pow(d, 1.4));
    else if (d <= 0.61) {
      return (0.0224 * ch0f - 0.031 * ch1f);
    else if (d <= 0.8) {
      return (0.0128 * ch0f - 0.0153 * ch1f);
    else if (d <= 1.3) {
      return (0.00146 * ch0f - 0.00112 * ch1f);
    else {
      return 0;

  static const byte REG_CONTROL = 0x00;
  static const byte REG_TIMING = 0x01;
  static const byte REG_THRESHLOWLOW = 0x02;
  static const byte REG_THRESHLOWHIGH = 0x03;
  static const byte REG_THRESHHIGHLOW = 0x04;
  static const byte REG_THRESHHIGHHIGH = 0x05;
  static const byte REG_INTERRUPT = 0x06;
  static const byte REG_CRC = 0x08;
  static const byte REG_ID = 0x0A;
  static const byte REG_DATA0LOW = 0x0C;
  static const byte REG_DATA0HIGH = 0x0D;
  static const byte REG_DATA1LOW = 0x0E;
  static const byte REG_DATA1HIGH = 0x0F;

  static const byte REG_COMMAND_CMD = 1 << 7;
  static const byte REG_COMMAND_CLEAR = 1 << 6;
  static const byte REG_COMMAND_WORD = 1 << 5;

  static const byte REG_CONTROL_POWER_ON = 0x03;

  static const byte REG_TIMING_GAIN_1 = 0 << 4;
  static const byte REG_TIMING_GAIN_16 = 1 << 4;
  static const byte REG_TIMING_START_CYCLE = 1 << 3;
  static const byte REG_TIMING_INTEGRATE_13_7MS = 0;
  static const byte REG_TIMING_INTEGRATE_101MS = 1;
  static const byte REG_TIMING_INTEGRATE_402MS = 2;

  static constexpr float TIMING_SCALE_13_7MS = 0.034;
  static constexpr float TIMING_SCALE_101MS = 0.252;
  static constexpr float TIMING_SCALE_402MS = 1;

  int i2cAddr;
  float gain;
  float integration;

APDS9301 apds9301;

/*************************** Sketch Code ************************************/

void setup() {
  pinMode(7, OUTPUT);


  Serial.println(F("Smart Bulb with MQTT Dash"));

  // Initialise the Client
  Serial.print(F("\nInit the Client..."));
  Ethernet.begin(mac, ip, myDns);
  delay(1000); //give the ethernet a second to initialize


// Function to connect and reconnect as necessary to the MQTT server.
// Should be called in the loop function and it will take care if connecting.
void MQTT_connect() {
  int8_t ret;

  // Stop if already connected.
  if (mqtt.connected()) {

  Serial.print("Connecting to MQTT... ");

  while ((ret = mqtt.connect()) != 0) { // connect will return 0 for connected
    Serial.println("Retrying MQTT connection in 5 seconds...");
    delay(5000);  // wait 5 seconds
  Serial.println("MQTT Connected!");

void loop() {
  // Ensure the connection to the MQTT server is alive (this will make the first
  // connection and automatically reconnect when disconnected).  See the MQTT_connect
  // function definition further below.

  //Get Lux values from APDS9301
  float lux; 
  if (apds9301.readLux(&lux)) {
    Serial.println("Luminosity: " + String(lux) + " lux");
  else {
    Serial.println("Cannot measure luminosity!");
  // Now we can publish stuff!
  Serial.print(F("\nSending lux value: "));
  if (! light.publish(lux++)) {
    Serial.println("Lux Failed");
  } else {
    Serial.println("Lux OK!");

  Adafruit_MQTT_Subscribe *subscription;
  while ((subscription = mqtt.readSubscription(1000))) {
    if (subscription == &lamp) {
      Serial.print(F("Got: "));

      char *received = (char *) lamp.lastread;
      if (lamp.lastread[0] == 49) {
        digitalWrite(7, HIGH);
        Serial.println(F("Lamp is now on"));
      else if (lamp.lastread[0] == 48) {
        digitalWrite(7, LOW);
        Serial.println(F("Lamp is now off"));

  // ping the server to keep the mqtt connection alive
  if (! {

In the above code, replace "yourusername" with your Adafruit IO username and "youradafruitiokey", with your Adafruit IO key which is present under My Key in Adafruit IO.

Before we can compile our code, we need to install a few libraries. First let's search for the Adafruit MQTT library. Go to your terminal and type:

pio lib search Adafruit MQTT

Platform IO will now search for the relevant libraries and provide us the results. Here we can see that we got the library we were looking for. We can see the Library ID at the top, in this case it is 1092. We will use this ID to install the library.

Type the following command in the terminal:

pio lib install 1092

This will install the Adafruit MQTT Library along with all of it's dependencies. Now we need to install the Ethernet library. Follow the same steps as before to install it via Platform IO.

pio lib search Ethernet #This is optional
pio lib install 872

Now we are ready to compile our code. Save the main.cpp file. We will again use Platform IO to compile our code. Go to your terminal and type the following command.

pio run

The first time this command is run, Platform IO will download and install the relevant framework and toolchains required for the STM32. This process will take a few seconds.

Now Platform IO will compile our code and output a firmware.bin file. We need to copy this firmware file from the .pio/build/nucleo_f411re to /workspace. Usually you would need to use the cp command, but we have created a custom command called load-firmware for ease of use. Just write the following command and the firmware.bin file will be copied to the workspace folder.


Once we have copied the firmware.bin file, all we need to do is to reset the STM32 by pressing the red button above the STM32.

After the reset, the STM32 will load the new firmware, and we should have a remote control that can be configured to work with any smart home gadget.

You can decrease the delay in the void loop to decrease the time between subsequent messages.

You can also use the Arduino IDE to work with the STM32. Follow our guide on Using STM32 with Arduino IDE and IoTIFY Virtual Lab.

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