Let’s see some basic functions related to Startup and GPIO that are frequently used in Energia IDE.

Functions at startup

a)  setup()

• This function is called at the beginning of the sketch.
• It is used for initializing variables, pin modes, etc.
• It runs only once after each power-up, or when the TI LaunchPad board resets.

b)  loop()

• Once the setup function is completed, the loop function is executed over and over continuously.

On-Board LED Blinking Code using MSP430 Launchpad

/* Blinking on-board LED connected to pin 2 of MSP-EXP430G2 Launchpad board */

/* Setup is run once at the start (Power-On or Reset) of sketch */
void setup()
{
    pinMode(2, OUTPUT); 	/* Pin 2 is defined as Output */
}

/* Loop runs over and over after the startup function */
void loop()
{
    digitalWrite(2, HIGH); 	/* Make pin 2 High, LED ON */
    delay(1000); 			/* Wait for 1 second */
    digitalWrite(2, LOW);	/* Make pin 2 Low, LED OFF*/
    delay(1000); 			/* Wait for 1 second */
}

Functions for using GPIO

a)  pinMode(pin, mode)

• pin: The pin for which a specific mode is selected
• mode: The mode for the pin specified in the function. It can be INPUT, INPUT PULLUP, INPUT PULLDOWN, or OUTPUT. 
• This function is used to configure the pin specified to behave as Input (INPUT), Input with pull up resistor (INPUT_PULLUP),  Input with a pull-down resistor (INPUT_PULLDOWN), or Output (OUTPUT).
• Example  

pinMode(3, INPUT); //configure digital pin 3 as an input pin.

b)  digitalRead(digital_pin)

• digital_pin: The digital pin which is to be read. 
• This function is used to read the digital signal from the specified digital pin (digital_pin).
• The function returns either HIGH or LOW.
• Example 

digitalRead(11); //reads value on pin 11. 

c)  digitalWrite(pin,value)

• pin: The digital pin to which value is to be written.
• value: Can be HIGH or LOW. 
• This function is used to write a HIGH or a LOW value to a digital pin.
• Example 

digitalWrite(12, HIGH); //makes the pin 12 HIGH. 

d)  analogRead(analog_pin)

• analog_pin: The analog pin whose value is to be read.
• This function is used to read the analog signal from the specified analog pin (analog_pin).
• The function returns an integer value in the range of 0 to 1023.
• Example 

analogRead(A3); //reads the value on analog pin A3. 

e)  analogWrite(pin,value)

• pin: The analogl pin to which value is to be written. 
• value: Can be any number between 0 to 255. 0 being 0% duty cycle and 255 being 100% duty cycle.
• This function is used for generating PWM on PWM digital pins.
• value can be any number between 0 to 255. 0 being 0% duty cycle and 255 being 100% duty cycle.
• Example 

analogWrite(10, 128); //generates a PWM wave of 50% duty cycle on pin 10.

LED Brightness Control using potentiometer Code using MSP430 Launchpad

/* Blink on-board LED connected to pin 2 of MSP-EXP430G2 Launchpad board */
/* Read analog value on analog pin A4 of MSP-EXP430G2 Launchpad board */
/* Read digital value on pin 6 of MSP-EXP430G2 Launchpad board */
/* Vary intensity of external LED connected to pin 11 of MSP-EXP430G2 Launchpad board */


/* Setup is run once at the start (Power-On or Reset) of sketch */
void setup()
{
    pinMode(2, OUTPUT); /* Pin 2 is defined as Output */
    pinMode(11, OUTPUT);  /* Pin 11 is defined as Output */
    pinMode(6, INPUT); /* Pin 6 is defined as Input */
}

/* Loop runs over and over after the startup function */
void loop()
{
    digitalWrite(2, HIGH); /* Make pin 2 High, LED ON */
    delay(1000); /* Wait for 1 second */
    digitalWrite(2, LOW); /* Make pin 2 Low, LED OFF*/
    delay(1000); /* Wait for 1 second */

    for(int i =0; i<256; i++)
    {
        analogWrite(11, i); /* Vary intensity of LED connected externally to pin 11 of MSP-EXP430G2 Launchpad board */
        /* Vary the intensity by applying PWM of duty cycle varying from 0 to 100% (writing value 0 to 255) */
        delay(300); /* Wait for 300 milliseconds */
    }

   int dig_val; 
   dig_val = digitalRead(6); /* Read digital signal on pin 8 */

    int adc_val;
    adc_val = analogRead(A4); /* Read analog signal present on pin A4 */
}