Just starting with this coming from a JS background.

I am looking into IoT development and wanted to set up my own repo without uploading the SSID and password of my personal WiFi.

Platform IO offers this `platformio.ini` as I understand to set `build_flags`.

```
  build_flags = 
     -D SSID="MySSID"

```

I don't know how to access them from my CPP file though. I want to inject the value from the build flag SSID into my \*.cpp file.

```
  #define SSID

  void loop()
  {
    Serial.println(SSID);
  }

```

The above doesn't write anything to the serial monitor.

What am I doing wrong? The code does compile.