TM4C123 UART

Programming UART on  ARM Cortex-m4 TM4C123 Tiva C LaunchPad 

In this example the TM4C123 micocontroller communicates with the PC by means of UART communication protocol. On the PC side, we need to download a serial terminal program to receive and send data from the pc. Tera Term is a highly recommended one, it can be downloaded just by doing a google search. After downloading and installing, follow the setup depicted in the two figures below.

When the program is opened, select the “Serial”  radio-button and in the drop-down select “COMx :Stellaris Virtual Serial Port” or any other port name you think relates to your microcontroller (the names in the drop-down vary sometimes)

Tera Term Serial Port Selection

Tera Term Serial Port Selection

 

Tera Term Serial Port Settings

Tera Term Serial Port Settings

This is the default setting but just to sure  go to  Setup -> Serial Port…

and verify.

In the program presented below, when any key is pressed in Tera terminal, the LEDs on the TM4C123 Tiva C launchpad either change color or go off depending on the ascii value of the key pressed . 

Note : The pressed key will not be printed in the terminal, just the LEDs will change.

 

Program :

#include "TM4C123.h" // Device header
#include <stdint.h>

char UART0Rx(void); 
void delayMs(int n);

int main(void) 
{
 char c;

 SYSCTL->RCGCUART |= 1; /* provide clock to UART0 */
 SYSCTL->RCGCGPIO |= 1; /* enable clock to PORTA */
 SYSCTL->RCGCGPIO |= 0x20; /* enable clock to PORTF */

 /* UART0 initialization */
 UART0->CTL = 0; /* disable UART0 */
 UART0->IBRD = 104; /* 16MHz/16=1MHz, 1MHz/104=9600 baud rate */
 UART0->FBRD = 11; /* fraction part, see Example 4-4 */
 UART0->CC = 0; /* use system clock */
 UART0->LCRH = 0x60; /* 8-bit, no parity, 1-stop bit, no FIFO */
 UART0->CTL = 0x301; /* enable UART0, TXE, RXE */

 /* UART0 TX0 and RX0 use PA0 and PA1. Set them up. */
 GPIOA->DEN = 0x03; /* Make PA0 and PA1 as digital */
 GPIOA->AFSEL = 0x03; /* Use PA0,PA1 alternate function */
 GPIOA->PCTL = 0x11; /* configure PA0 and PA1 for UART */

 GPIOF->DIR = 0x0E; /* configure Port F to control the LEDs */
 GPIOF->DEN = 0x0E;
 GPIOF->DATA = 0;

 for(;;)
 {
 c = UART0Rx(); /* get a character from UART */
 GPIOF->DATA = c << 1; /* shift left and write it to LEDs */ } } /* UART0 Receive */ /* This function waits until a character is received then returns it. */ char UART0Rx(void) { char c; while((UART0->FR & 0x10) != 0); /* wait until the buffer is not empty */
 c = UART0->DR; /* read the received data */
 return c; /* and return it */
}

/* Append delay functions and SystemInit() here */
void delayMs(int n){
int i,j; 

 for(i=0;i<n;i++){
 for(j=0;j<3180;j++)
 {}
 }
}

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