UART 115200 with serial terminal

Quote from lvivgeorge on November 18, 2024, 6:37 am

Hi!

I was wondering if there are any known issues or limitations with simulating UART at a 115200 baud rate.

I've tested 9600, 19200, 38400, and 57600—all of them work fine. However, higher baud rates like 115200 and 230400 do not seem to work.

My code

#include <avr/io.h>

#include <util/delay.h>

#include <stdio.h>

#include <stdbool.h>

#define F_CPU 16000000UL // Clock speed

#define BAUD 115200

#define BAUDRATE ((F_CPU / (BAUD * 16UL)) - 1)

#define LED PB5

void uartInit(void);

void uartTransmit(char data);

char uartReceive(void);

void uartSendString(const char *str);

void lightLed(uint8_t n);

int main(void) {

DDRB|=1<<LED;

charbuffer[50]; // Buffer to hold the message

uartInit(); // Initialize UART

boolisCorrect=false;

 

while (1) {

charreceived=uartReceive(); // Receive a byte

 

// Check if the received byte is between '1' and '9'

if (received>='1'&&received<='9') {

isCorrect=true;

// Prepare a message with the number

sprintf(buffer, "Success! You entered: %c\r\n", received);

} else {

isCorrect=false;

sprintf(buffer, "Invalid input. Please send a number between 1-9.\r\n");

}

 

uartSendString(buffer);

if (isCorrect) {

uint8_tn=received-'0';

lightLed(n);

}

_delay_ms(1000);

}

}

// Initialize UART

void uartInit(void) {

// Set baud rate

UBRR0H= (BAUDRATE>>8);

UBRR0L=BAUDRATE;

// Enable transmitter and receiver

UCSR0B= (1<<RXEN0) | (1<<TXEN0);

// Set frame format: 8 data bits, 1 stop bit

UCSR0C= (1<<UCSZ01) | (1<<UCSZ00);

}

// Send a byte via UART

void uartTransmit(char data) {

// Wait for empty transmit buffer

while (!(UCSR0A& (1<<UDRE0)));

// Put data into buffer, sends the data

UDR0=data;

}

// Receive a byte via UART

char uartReceive(void) {

// Wait for data to be received

while (!(UCSR0A& (1<<RXC0)));

// Get and return received data from buffer

returnUDR0;

}

// Send a string via UART

void uartSendString(const char *str) {

while (*str) {

uartTransmit(*str++);

}

}

void lightLed(uint8_t n) {

for (uint8_ti=0; i<n; i++) {

PORTB|=1<<LED;

_delay_ms(200);

PORTB&=~(1<<LED);

_delay_ms(200);

}

}