How to send and receive data through UART between two Arduino Unos - c

Question

I have been working through this problem for quite some time now and have succeeded in getting a partial mark. I would like to know what is wrong with the code that I have, that is preventing me from succeeding under certain conditions
I need one arduino to communicate with another one by sending a string of characters. So far I have succeeded in sending and receiving some data but think that I may be having an issue with the buffer I have set up in my uart_receive_string() function. I will provide all of the necessary information and code needed in order to test this, just let me know if any more info is required and Ill be happy to provide.
Here is a link to the tinkercad driver: https://www.tinkercad.com/things/eUZqkaIHp6J
Just click "Copy and Tinker" and hit the code button up top in order to paste the below code into it. You will need to paste the code into both ardunios by selecting them via the drop down box.
This is the criteria for the question I am working on:
This is the output I should receive in the test driver provided:
Here is the current code that I have implemented:
It is what needs to be copied into tinkercad for both arduino's
#include <stdint.h>
#include <stdio.h>
#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>
void uart_putbyte(unsigned char data);
int uart_getbyte(unsigned char *buffer);
/*
** Define a function named uart_send_string which transmits the contents of
** a standard C string (i.e. a null-terminated char array) over UART. The
** function should iterate over the characters in the array, using a cast to
** convert each to an unsigned char, and transmitting the resulting byte via
** uart_putbyte. The end of the string should be signalled by sending a single
** null byte. That is, the number 0, not the character '0'.
**
** Param: str - string to be transmitted.
**
** Returns: Nothing.
*/
// vvvvvvv I need help with this vvvvvvv
void uart_send_string(char str[])
{
int i = 0;
char ch;
do{
ch = str[i];
uart_putbyte(ch);
i++;
}while(ch != '\0');
}
/*
** Define a function named uart_receive_string which uses uart_getbyte to fetch
** the contents of a standard C string (i.e. a null-terminated char array)
** from UART. The function should wait for characters, and must not return
** until a complete string has been retrieved.
**
** Note that uart_getbyte will return 1 if a byte is available, and zero
** otherwise. Therefore, to fetch a byte and store it in a variable named x,
** you will need to use a construct of the form:
** unsigned char x;
** while (! uart_getbyte(&x)) {
** // Do nothing.
** }
**
** Param: buffer - a char array which has capacity to store a string
** containing at most (buff_len-1) characters. If more than (buff_len-1)
** characters are received, the first (buff_len-1) of them should be
** stored consecutively in the buffer, and any others discarded. The
** string must be terminated correctly with a null terminator in all
** circumstances.
**
** Param: buff_len - an int which specifies the capacity of the buffer.
**
** Returns: Nothing. However, up to buff_len elements of buffer may have been
** overwritten by incoming data.
*/
//vvvvvvv I need help with this vvvvvvv
void uart_receive_string(char buffer[], int buff_len)
{
int i = 0;
unsigned char ch;
while(!uart_getbyte(&ch))
{
if(ch == 0)
{
break;
}
if(i < buff_len-1)
{
ch = buffer[i];
uart_putbyte(ch);
i++;
}
}
buffer[i]=0;
}
/*
***************************************************************************
** Initialise UART.
***************************************************************************
*/
void uart_init(void) {
UBRR0 = F_CPU / 16 / 9600 - 1;
UCSR0A = 0;
UCSR0B = (1 << RXEN0) | (1 << TXEN0);
UCSR0C = (3 << UCSZ00);
}
/*
**************************************************************************
** Send one byte, protecting against overrun in the transmit buffer.
**
** Param: data - a byte to be transmitted.
**
** Returns: Nothing.
***************************************************************************
*/
#ifndef __AMS__
void uart_putbyte(unsigned char data) {
// Wait for empty transmit buffer
while (!(UCSR0A & (1 << UDRE0)));
// Send data by assigning into UDR0
UDR0 = data;
}
#endif
/*
***************************************************************************
** Attempt to receive one byte, returning immediately to sender.
**
** Param: buffer - the address of a byte in which a result may be stored.
**
** Returns: If a byte is available returns 1 and stores the incoming byte in
** location referenced by buffer. Otherwise returns 0 and makes no other
** change to the state.
***************************************************************************
*/
#ifndef __AMS__
int uart_getbyte(unsigned char *buffer) {
// If receive buffer contains data...
if (UCSR0A & (1 << RXC0)) {
// Copy received byte from UDR0 into memory location (*buffer)
*buffer = UDR0;
//
return 1;
}
else {
return 0;
}
}
#endif
/*
***************************************************************************
** Implement main event loop.
***************************************************************************
*/
void process() {
// Use two devices, as indicated in the supplied TinkerCad model. One
// device acts as the sender (is_sender = 1), the other as receiver
// (is_sender = 0). Change this to set the role accordingly.
const int is_sender = 1;
if (is_sender) {
static char * messages_to_send[] = {
"", // Empty string
"A", // String with one symbol.
"Hello from CAB202!", // Multiple symbols
"1234567890abcdefghijklmnopqrstuvwxyz", // Longer than buffer size.
NULL, // End of list
};
static int next_message = 0;
uart_send_string(messages_to_send[next_message]);
next_message ++;
if (messages_to_send[next_message] == NULL) next_message = 0;
_delay_ms(300);
}
else {
#define BUFF_SIZE 20
char buffer[BUFF_SIZE];
uart_receive_string(buffer, BUFF_SIZE);
uart_send_string(buffer);
uart_putbyte('\r');
uart_putbyte('\n');
}
}
int main(void) {
uart_init();
while (1) {
process();
}
return 0;
}
The areas of this code that I am required to work on are these:
This is needed to send the data:
void uart_send_string(char str[])
{
int i = 0;
char ch;
do{
ch = str[i];
uart_putbyte(ch);
i++;
}while(ch != '\0');
}
This is needed to receive the data:
void uart_receive_string(char buffer[], int buff_len)
{
int i = 0;
unsigned char ch;
while(!uart_getbyte(&ch))
{
if(ch == 0)
{
break;
}
if(i < buff_len-1)
{
ch = buffer[i];
uart_putbyte(ch);
i++;
}
}
buffer[i]=0;
}
I am really sorry if this is hard to understand. Ill do my best to clarify any additional information that is needed. I just need to figure out what I am doing incorrectly.