add blinky and more setup details

1_Basic_GPIO/blinky.md

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+## Blinky
+
+The classic, the helloWorld of embedded programming. This program turns the LED on and off periodically.
+
+### Initial steps: 
+- Create new project with project generator.
+- Open the project folder in VSCode.
+- Build the project by pressing the `build` button at the bottom and select the option with `arm-none-eabi`.
+- Make sure the build exits with code 0.
+
+<img src="../assets/buildButton.png" width="300">
+
+### Basic Code:
+
+``` C
+int main()
+{
+    stdio_init_all();
+
+    const uint OnBoardLED = PICO_DEFAULT_LED_PIN;
+    gpio_init(OnBoardLED);
+    gpio_set_dir(OnBoardLED, GPIO_OUT);
+    while (true){
+        gpio_put(OnBoardLED, true);
+        sleep_ms(500);
+        gpio_put(OnBoardLED, false);
+        sleep_ms(500);
+    }
+}
+```
+
+#### Explanation:
+`stdio_init_all()`: initialize stuff
+
+`OnBoardLED = PICO_DEFAULT_LED_PIN`: Get the GPIO number of onboard LED. Remember this is GPIO Number, NOT PIN NUMBER.
+
+`gpio_init(OnBoardLED)`: Initialize that GPIO pin.
+
+`gpio_set_dir(OnBoardLED, GPIO_OUT)`: Set GPIO direction (`GPIO_OUT` for writing and `GPIO_IN` for reading).
+
+`while (true){}`: Super loop of the program
+
+`gpio_put(OnBoardLED, true)`: Set `OnBoardLED` pin to `on` (`true` to turn on/set to high/voltage to VDD, `false` to turn off/set to low/voltage to GND)
+
+Pico login HIGH voltage is 3.3v and LOW voltage is 0v.
+
+`sleep_ms(500)`: sleep for 500ms.
+
+---
+