Facebook
Google
GitHub
Linkedin
i am just starting with microcontrollers so i don't know much about them to begin with.but as of now i am learning to configure uart hardware registers for serial communication and i seem to be stuck with weird strange characters being printed on my serial terminal. I am using avr328p-pu(extracted from an arduino uno board) with an external 16mhz oscillator and a usb to ttl converter(5V) for usb to serial conversion. I'm not using the power supply that comes with the usb-ttl adaptor instead i am using the powerline pins on arduino board as for the circuit diagram i will upload it and the code that i am using as well.
Initially i thought that my baud rate is messed up somehow because of that i hardcoded the baud rate in the registers using a baud rate calculator for 16mhz clock cycle you will see that in the code. could it be that i am using long jumper wires which could cause some noise?
can anyone help with this another thing that i noticed was when i unplug the power from the board the chip is still powered from the usb-ttl adaptor even though i am not using it's 5V power supply pin can anyone look at the circuit and explain that to me as well.
i am using coolTerm for serial Terminal and it is set to 9600
Initially i thought that my baud rate is messed up somehow because of that i hardcoded the baud rate in the registers using a baud rate calculator for 16mhz clock cycle you will see that in the code. could it be that i am using long jumper wires which could cause some noise?
can anyone help with this another thing that i noticed was when i unplug the power from the board the chip is still powered from the usb-ttl adaptor even though i am not using it's 5V power supply pin can anyone look at the circuit and explain that to me as well.
i am using coolTerm for serial Terminal and it is set to 9600
serialCom.c:
#include<avr/io.h>
#include<util/delay.h>
#include "USART.h"
int main(void){
char serialcharacter;
DDRB|=(1<<0)|(1<<1)|(1<<2);
initUSART();
while(1){
serialcharacter = receiveByte();
transmitByte(serialcharacter);
PORTB=serialcharacter&(255>>5); /*get the 3 most significant bits*/
}
}
USART.h:
/* Functions to initialize, send, receive over USART
initUSART requires BAUD to be defined in order to calculate
the bit-rate multiplier.
*/
#ifndef BAUD /* if not defined in Makefile... */
#define BAUD 9600 /* set a safe default baud rate */
#endif
/* These are defined for convenience */
#define USART_HAS_DATA bit_is_set(UCSR0A, RXC0)
#define USART_READY bit_is_set(UCSR0A, UDRE0)
/* Takes the defined BAUD and F_CPU,
calculates the bit-clock multiplier,
and configures the hardware USART */
void initUSART(void);
/* Blocking transmit and receive functions.
When you call receiveByte() your program will hang until
data comes through. We'll improve on this later. */
void transmitByte(uint8_t data);
uint8_t receiveByte(void);
void printString(const char myString[]);
/* Utility function to transmit an entire string from RAM */
void readString(char myString[], uint8_t maxLength);
/* Define a string variable, pass it to this function
The string will contain whatever you typed over serial */
void printByte(uint8_t byte);
/* Prints a byte out as its 3-digit ascii equivalent */
void printWord(uint16_t word);
/* Prints a word (16-bits) out as its 5-digit ascii equivalent */
void printBinaryByte(uint8_t byte);
/* Prints a byte out in 1s and 0s */
char nibbleToHex(uint8_t nibble);
char nibbleToHexCharacter(uint8_t nibble);
void printHexByte(uint8_t byte);
/* Prints a byte out in hexadecimal */
uint8_t getNumber(void);
/* takes in up to three ascii digits,
converts them to a byte when press enter */
USART.c:
#include <avr/io.h>
#include "USART.h"
#include <util/setbaud.h>
void initUSART(void) { /* requires BAUD */
UBRR0H = 0x00; /* defined in setbaud.h */
UBRR0L = 0x67;
#if USE_2X
UCSR0A |= (1 << U2X0);
#else
UCSR0A &= ~(1 << U2X0);
#endif
/* Enable USART transmitter/receiver */
UCSR0B = (1 << TXEN0) | (1 << RXEN0);
UCSR0C = (1 << UCSZ01) | (1 << UCSZ00); /* 8 data bits, 1 stop bit */
}
void transmitByte(uint8_t data) {
/* Wait for empty transmit buffer */
loop_until_bit_is_set(UCSR0A, UDRE0);
UDR0 = data; /* send data */
}
uint8_t receiveByte(void) {
loop_until_bit_is_set(UCSR0A, RXC0); /* Wait for incoming data */
return UDR0; /* return register value */
}
/* Here are a bunch of useful printing commands */
void printString(const char myString[]) {
uint8_t i = 0;
while (myString[i]) {
transmitByte(myString[i]);
i++;
}
}
void readString(char myString[], uint8_t maxLength) {
char response;
uint8_t i;
i = 0;
while (i < (maxLength - 1)) { /* prevent over-runs */
response = receiveByte();
transmitByte(response); /* echo */
if (response == '\r') { /* enter marks the end */
break;
}
else {
myString[i] = response; /* add in a letter */
i++;
}
}
myString[i] = 0; /* terminal NULL character */
}
void printByte(uint8_t byte) {
/* Converts a byte to a string of decimal text, sends it */
transmitByte('0' + (byte / 100)); /* Hundreds */
transmitByte('0' + ((byte / 10) % 10)); /* Tens */
transmitByte('0' + (byte % 10)); /* Ones */
}
void printWord(uint16_t word) {
transmitByte('0' + (word / 10000)); /* Ten-thousands */
transmitByte('0' + ((word / 1000) % 10)); /* Thousands */
transmitByte('0' + ((word / 100) % 10)); /* Hundreds */
transmitByte('0' + ((word / 10) % 10)); /* Tens */
transmitByte('0' + (word % 10)); /* Ones */
}
void printBinaryByte(uint8_t byte) {
/* Prints out a byte as a series of 1's and 0's */
uint8_t bit;
for (bit = 7; bit < 255; bit--) {
if (bit_is_set(byte, bit))
transmitByte('1');
else
transmitByte('0');
}
}
char nibbleToHexCharacter(uint8_t nibble) {
/* Converts 4 bits into hexadecimal */
if (nibble < 10) {
return ('0' + nibble);
}
else {
return ('A' + nibble - 10);
}
}
void printHexByte(uint8_t byte) {
/* Prints a byte as its hexadecimal equivalent */
uint8_t nibble;
nibble = (byte & 0b11110000) >> 4;
transmitByte(nibbleToHexCharacter(nibble));
nibble = byte & 0b00001111;
transmitByte(nibbleToHexCharacter(nibble));
}
uint8_t getNumber(void) {
// Gets a numerical 0-255 from the serial port.
// Converts from string to number.
char hundreds = '0';
char tens = '0';
char ones = '0';
char thisChar = '0';
do { /* shift over */
hundreds = tens;
tens = ones;
ones = thisChar;
thisChar = receiveByte(); /* get a new character */
transmitByte(thisChar); /* echo */
} while (thisChar != '\r'); /* until type return */
return (100 * (hundreds - '0') + 10 * (tens - '0') + ones - '0');
}
