Tiva C Projects: Blinking External LED on PORTA

In the previous instructable, we made blinking built-in LED on PORTF link

In this instructable, we will make the blinking external LED on PORTA and give instructions for different ports.

Let`s do it

• Tiva C board (TM4C123G)
• LED
• Resistor (330 Ohms)
• Jumpers

• Connect 330Ohms resistor with PA2
• Connect the other pin of 330Ohms resistor to positive pin of LED
• Connect the negative pin of LED with GND on Tiva C Board

The base address of PORTA is 0x40004000 so we should look at the offset of different registers and add the offset to the base address of PORTA

Example: the offset of direction register is 0x400 so 0x40004000 + 0x400 = 0x40004400

and so on for different registers. look at the previous instructable if you want

link of the previous instructable: https://www.instructables.com/Blinking-LED-in-Tiva...

//define part

#define SYSCTL_RCGCGPIO_R (*((volatile int *) 0x400FE608))

#define GPIO_PORTA_DEN_R (*((volatile int *) 0x4000451C))

#define GPIO_PORTA_DIR_R (*((volatile int *) 0x40004400))

#define GPIO_PORTA_DATA_R (*((volatile int *) 0x40004010))

#define GPIO_PORTA_AMSEL_R (*((volatile int *) 0x40004528))

#define GPIO_PORTA_AFSEL_R (*((volatile int *) 0x40004420))

#define GPIO_PORTA_PCTL_R (*((volatile int *) 0x4000452C))

For clock enable, there is a table to help you

PORTA --> 0x01 , PORTB --> 0x02 , PORTC --> 0x04 , PORTD --> 0x08 , PORTE --> 0x10 , PORTF --> 0x20

#define GPIO_PORTA_CLK_EN 0x01 //enable clock for PORTA
#define GPIO_PORTA_PIN2_EN 0x04 //enable pin 2 of PORTA

#define LED_ON2 0x04 //turn on LED on Pin 2 PORTA

#define LED_OFF2 0x00 //turn off LED on Pin 2 PORTA

void Delay(unsigned int);

int main (void)

{

SYSCTL_RCGCGPIO_R |= GPIO_PORTA_CLK_EN; //activate clock for Port A
Delay(10); //Delay 10 msec to allow

clock to start on PORTA

GPIO_PORTA_DEN_R |= GPIO_PORTA_PIN2_EN; // Enable pin 2 of PORTA

GPIO_PORTA_DIR_R |= GPIO_PORTA_PIN2_EN; // Make pin 2 of PORTA as ouptut pin GPIO_PORTA_PCTL_R &= ~GPIO_PORTA_PIN2_EN; // Regular GPIO of PORTA

GPIO_PORTA_AMSEL_R &= ~GPIO_PORTA_PIN2_EN; // Disable analog function on pin 2 of PORTA GPIO_PORTA_AFSEL_R &= ~GPIO_PORTA_PIN2_EN; // Regular port function

while(1)
{ GPIO_PORTA_DATA_R = LED_ON2; //Turn on Blue LED

Delay(1000); //Delay almost 1 sec

GPIO_PORTA_DATA_R = LED_OFF2; //Turn off LED

Delay(1000); //Delay almost 1 sec }

}

void Delay(unsigned int delay)
{ volatile unsigned int i, counter;

counter = delay * 4000; // 1 second (1000 msec) needs 40000000 counter so 4000000/1000 = 4000

for(i=0;I<counter;i++);

}

You must change the following:

• Look at the base address of the port you want to work on. For example: PORTB -> base address is 0x40005000
• change the define part in the code corresponding to the new port.
• change the value of GPIO DATA register if you want to work on different pin (ex: for pin 3 --> 0b0000100000 and convert it to hex 0x20 and adding to the base address of the port)
• change GPIO clock enable from 0x01 (for PORTA ) to new value of the new port (ex: for PORTB -> 0x02)
• change GPIO enable pin from 0x04 (for pin 2) if you want to work on a different pin (ex: for pin 3 --> 0x08)
• change the circuit diagram.