Lesson 15: Universal Asynchronous Receiver Transmitter (UART)

By default, the Keil μVision will configure the system clock to 50 MHz for EK-TM4C123G LaunchPad.

Using PA0 and PA1 to communicate with PC through ICDC virtual COM port. The configuration of UART is: 115200bps, 8-bit data, No parity check, 1-stop bit.

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <stdint.h>

#include "TM4C123GH6PM.h"

void Setup_UART0();
void Setup_GPIO();
void Delay(int s);

int main(void)
{
    char ch;
    char chNewLine = 10;
    char chReturn  = 13;
    int  i;

    Setup_UART0();
    Setup_GPIO();

    while (1){
        ch = 'A';
        for (i = 0; i < 26; i++){
            while ((UART0->FR & ____) == ____) {};
            UART0->DR = ch;
            Delay(10);    // Software Delay
            ch ++;
        }
        while ((UART0->FR & ____) == ____) {};
        UART0->DR = chNewLine;
        while ((UART0->FR & ____) == ____) {};
        UART0->DR = chReturn;
        Delay(100);       // Software Delay
    }
}

void Setup_UART0() // UART Setting=115200,8N1
{
    int BRDI = __;
    int BRDF = __;

    // 1. Enable clock to UART Module (SYSCTL_RCGCUART)
    SYSCTL->RCGCUART |= (__);
    // allow time for clock to stabilize
    while ((SYSCTL->PRUART & (__) ) != (__)){};
    // 2. Disable UART by clearing UARTEN in UARTCTL register
    UART0->CTL &= ~(__);
    // 3. Write BRD to UARTIBRD and UARTFBRD register
    UART0->IBRD = BRDI;
    UART0->FBRD = BRDF;
    // 4. Write UART Line Control, High Byte (UARTLCRH register)
    //    8bit, No parity, 1-stop bit, no FIFO = 0x00000060
    UART0->LCRH = ____;
    // 5. Configure the UART clock source (UARTCC register)
    UART0->CC = 0x00;   // Clock Source from System Clock
    // 6. Enable UART by clearing UARTEN in UARTCTL register
    UART0->CTL = ____; // Enable UART0, TXE, RXE
}
void Setup_GPIO()
{
    // Enable PA0, PA1 for UART
    // GPIO Initialization and Configuration
    // 1. Enable Clock to the GPIO Modules (SYSCTL->RCGCGPIO |= (_PORTs);)
    SYSCTL->RCGCGPIO |= (_PORTs); |= (__);   // PortA
    // allow time for clock to stabilize (SYSCTL->PRGPIO)
    while ((SYSCTL->PRGPIO & (__)) != (__) ){};

    // 2. Unlock GPIO only PD7, PF0 on TM4C123G; PD7, PE7 on TM4C1294 (GPIOx->LOCK = 0x4C4F434B; and GPIOx->CR = _PINs;)
    // 3. Set Analog Mode Select bits for each Port (GPIOx->AMSEL = _PINs; 0=digital, 1=analog)
    // 4. Set Port Control Register for each Port (GPIOx->PCTL = PMCn << _PTCL_PINn, check the PCTL table)
    GPIOA->PCTL = ____;
    // 5. Set Alternate Function Select bits for each Port (GPIOx->AFSEL = _PINs; 0=regular I/O, 1=PCTL peripheral)
    GPIOA->AFSEL |= ____;
    // 6. Set Output pins for each Port (Direction of the Pins: GPIOx->DIR = _PINs; 0=input, 1=output)
    // 7. Set PUR bits for internal pull-up, PDR for pull-down reg, ODR for open drain (0: disable, 1=enable)
    // 8. Set Digital ENable register on all GPIO pins (GPIOx->DEN = _PINs; 0=disable, 1=enable)
    GPIOA->DEN = ____;
}
void Delay(int s)
{
    volatile int i, j;
    for (i = 0; i < s; i++)
        for (j = 0; j < 3180; j++) {};
}

The default System Clock is 16MHz. Using PA0 and PA1 to communicate with PC through ICDC virtual COM port. The configuration of UART is: 115200bps, 8-bit data, No parity check, 1-stop bit

After power-on-reset, the system clock is 16MHz for TM4C1294 LaunchPad.

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <stdint.h>

#include "TM4C1294NCPDT.h"

void Setup_UART0();
void Delay(int s);

int main(void)
{
    char    ch = 'A';
    char    chNewLine = 10;
    char    chReturn  = 13;
    int     i;

    Setup_UART0();
    Setup_GPIO();

    while (1){
        ch = 'A';
        for (i = 0; i < 26; i++){
            while ((UART0->FR & ____) == ____) {};
            UART0->DR = ch;
            Delay(10);
            ch ++;
        }
        while ((UART0->FR & ____) == ____) {};
        UART0->DR = chNewLine;
        while ((UART0->FR & ____) == ____) {};
        UART0->DR = chReturn;
        Delay(100);
    }
}

void Setup_UART0() // UART Setting=115200,8N1
{
    int BRDI = 8;
    int BRDF = 44;

    // 1. Enable clock to UART Module (SYSCTL_RCGCUART)
    SYSCTL->RCGCUART |= (__);
    // allow time for clock to stabilize
    while ((SYSCTL->PRUART & (__)) != (__)){};

    // 2. Select the baud clock source for UART module
    UART0->CC = 0x0;  // Buad clock source from system clock
    // 3. Disable UART by clearing UARTEN in UARTCTL register
    UART0->CTL &= ~(__);
    // 4. Write BRD to UARTIBRD and UARTFBRD register
    UART0->IBRD = BRDI;
    UART0->FBRD = BRDF;
    // 5. Write UART Line Control, High Byte (UARTLCRH register)
    //    8bit, No parity, 1-stop bit, no FIFO = 0x00000060
    UART0->LCRH = ___;
    // 6. Configure the UART clock source (UARTCC register)
    UART0->CC = 0x00;   // Clock Source from System Clock
    // 7. Enable UART by clearing UARTEN in UARTCTL register
    UART0->CTL = ___; // Enable UART0, TXE, RXE
}
void Setup_GPIO()
{
    // Enable PA0, PA1 for UART
    // GPIO Initialization and Configuration
    // 1. Enable Clock to the GPIO Modules (SYSCTL->RCGCGPIO |= (_PORTs);)
    SYSCTL->RCGCGPIO |= (_PORTs); |= (__);   // PortA
    // allow time for clock to stabilize (SYSCTL->PRGPIO)
    while ((SYSCTL->PRGPIO & (__)) != (__)) {};

    // 2. Unlock GPIO only PD7, PF0 on TM4C123G; PD7, PE7 on TM4C1294 (GPIOx->LOCK = 0x4C4F434B; and GPIOx->CR = _PINs;)
    // 3. Set Analog Mode Select bits for each Port (GPIOx->AMSEL = _PINs; 0=digital, 1=analog)
    // 4. Set Port Control Register for each Port (GPIOx->PCTL = PMCn << _PTCL_PINn, check the PCTL table)
    GPIOA_AHB->PCTL = ___;
    // 5. Set Alternate Function Select bits for each Port (GPIOx->AFSEL = _PINs; 0=regular I/O, 1=PCTL peripheral)
    GPIOA_AHB->AFSEL |= ___;
    // 6. Set Output pins for each Port (Direction of the Pins: GPIOx->DIR = _PINs; 0=input, 1=output)
    // 7. Set PUR bits for internal pull-up, PDR for pull-down resister, ODR for open drain (0: disable, 1=enable)
    // 8. Set Digital ENable register on all GPIO pins (GPIOx->DEN = _PINs; 0=disable, 1=enable)
    GPIOA_AHB->DEN = ___;
}
void Delay(int s)
{
    volatile int i, j;
    for (i = 0; i < s; i++)
        for (j = 0; j < 3180; j++) {};
}