usart.c File Reference

Driver file providing core USART communication between the target MCU and your PC. This file was adapted from Elliot Williams' Github repo hexagon5un. (link in the see also section below). More...

#include <util/setbaud.h>
#include <avr/io.h>
#include "usart.h"

Go to the source code of this file.

Functions
void	init_usart (void)
	Takes the defined BAUD and F_CPU, calculates the bit-clock multiplier, configures the hardware USART ready for use. More...
void	usart_print_string (const char myString[])
	Utility function to transmit a string. More...
void	usart_read_string (char myString[], uint8_t maxLength)
	Define a string variable, pass it to this function. More...
void	usart_print_byte (uint8_t byte)
	Prints a byte out as its 3-digit ascii equivalent. More...
void	usart_print_decimal_digit (uint8_t byte)
	Prints a byte out as its 1-digit ascii equivalent. More...
void	usart_print_char (char byte)
	Prints a byte out as its 1-character ascii equivalent. More...
void	usart_print_word (uint16_t word)
	Prints a word (16-bits) out as its 5-digit ascii equivalent. More...
void	usart_print_binary_byte (uint8_t byte)
	Prints a byte out in 1s and 0s. More...
char	usart_nibble_to_hex_character (uint8_t nibble)
	Convert a nibble to a hex character. More...
void	usart_print_hex_byte (uint8_t byte)
	Prints a byte out in hexadecimal format. More...
uint8_t	usart_get_number (void)
	Takes in up to three ascii digits, converts them to a byte when press enter. More...

Detailed Description

Driver file providing core USART communication between the target MCU and your PC. This file was adapted from Elliot Williams' Github repo hexagon5un. (link in the see also section below).

Copyright

Copyright © 2022 by Jason Duffy.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Author

Jason Duffy

Date

15th March 2022

See also

https://github.com/hexagon5un/AVR-Programming

Definition in file usart.c.

Function Documentation

init_usart()

void init_usart

(

void

)

Takes the defined BAUD and F_CPU, calculates the bit-clock multiplier, configures the hardware USART ready for use.

Takes the defined BAUD and F_CPU, calculates the bit-clock multiplier, configures the hardware USART.

Definition at line 50 of file usart.c.

{
  // defined in setbaud.h
  UBRR0H = UBRRH_VALUE;
  UBRR0L = UBRRL_VALUE;
 
#if USE_2X
  UCSR0A |= (1 << U2X0);
#else
  UCSR0A &= ~(1 << U2X0);
#endif
  
  // Enable USART transmitter/receiver
  UCSR0B = (1 << TXEN0) | (1 << RXEN0);
  // 8 data bits, 1 stop bit
  UCSR0C = (1 << UCSZ01) | (1 << UCSZ00);
}

usart_print_string()

void usart_print_string

(

const char

my_string[]

)

Utility function to transmit a string.

Parameters

my_string

is the string constant youd like to print, and should be enclosed in "" quotation marks.

Definition at line 74 of file usart.c.

{
  uint8_t i = 0;
  while (myString[i])
  {
    transmit_byte(myString[i]);
    i++;
  }
}

usart_read_string()

void usart_read_string	(	char	my_string[],
		uint8_t	max_length
	)

Define a string variable, pass it to this function.

The string will contain. whatever you typed over serial.

Parameters

my_string	is a pointer to the first element in the character array you'd like to store the received message in.
max_length	is the maximum number of characters expected.

Definition at line 92 of file usart.c.

{
  char response;
  uint8_t count = 0;
 
  while (count < (maxLength - 1))
  {                  
    response = receive_byte();
    transmit_byte(response); // echo
 
    if (response == '\r') // enter marks the end
    {
      break;
    }
 
    else
    {
      myString[count] = response; // add in a letter
      ++count;
    }
  }
  myString[count] = 0; // terminal NULL character */
}

usart_print_byte()

void usart_print_byte

(

uint8_t

byte

)

Prints a byte out as its 3-digit ascii equivalent.

Parameters

byte	is the 8 bits of data to be sent, must be unsigned.

Definition at line 121 of file usart.c.

{
  // Converts a byte to a string of decimal text, sends it
  if (byte > 99)
  {
    transmit_byte('0' + (byte / 100));      // Hundreds
  }
  if (byte > 9)
  {
    transmit_byte('0' + ((byte / 10) % 10));   // Tens
  }
  transmit_byte('0' + (byte % 10));     // Ones
}

usart_print_decimal_digit()

void usart_print_decimal_digit

(

uint8_t

byte

)

Prints a byte out as its 1-digit ascii equivalent.

Parameters

byte	is the 8 bits of data to be sent, must be unsigned, with a value of 0-9;

Definition at line 141 of file usart.c.

{
  transmit_byte(byte);
}

usart_print_char()

void usart_print_char

(

char

byte

)

Prints a byte out as its 1-character ascii equivalent.

Parameters

byte	is the character to be sent.

Definition at line 151 of file usart.c.

{
  transmit_byte(byte);
}

usart_print_word()

void usart_print_word

(

uint16_t

word

)

Prints a word (16-bits) out as its 5-digit ascii equivalent.

Parameters

word	is the 16 bits of data to be sent, must be unsigned.

Definition at line 161 of file usart.c.

{
  transmit_byte('0' + (word / 10000));       // Ten-thousands
  transmit_byte('0' + ((word / 1000) % 10)); //  Thousands
  transmit_byte('0' + ((word / 100) % 10));  //  Hundreds
  transmit_byte('0' + ((word / 10) % 10));   //  Tens
  transmit_byte('0' + (word % 10));          //  Ones
}

usart_print_binary_byte()

void usart_print_binary_byte

(

uint8_t

byte

)

Prints a byte out in 1s and 0s.

Parameters

byte	is the 8 bits of data to be sent, must be unsigned.

Definition at line 175 of file usart.c.

{
  uint8_t bit;
  for (bit = 7; bit < 255; bit--)
  {
    if (bit_is_set(byte, bit))
    {
      transmit_byte('1');
    }
    else
    {
      transmit_byte('0');
    }
  }
}

usart_nibble_to_hex_character()

char usart_nibble_to_hex_character

(

uint8_t

nibble

)

Convert a nibble to a hex character.

Parameters

nibble

is the 4 bits of data to be sent, must be unsigned.

Definition at line 196 of file usart.c.

{
  if (nibble < 10)
  {
    return ('0' + nibble);
  }
  else
  {
    return ('A' + nibble - 10);
  }
}

usart_print_hex_byte()

void usart_print_hex_byte

(

uint8_t

byte

)

Prints a byte out in hexadecimal format.

Parameters

byte	is the 8 bits of data to be sent, must be unsigned.

Definition at line 213 of file usart.c.

{
  uint8_t nibble;
  nibble = (byte & 0b11110000) >> 4;
  transmit_byte(usart_nibble_to_hex_character(nibble));
  nibble = byte & 0b00001111;
  transmit_byte(usart_nibble_to_hex_character(nibble));
}

usart_get_number()

uint8_t usart_get_number

(

void

)

Takes in up to three ascii digits, converts them to a byte when press enter.

Returns

an unsigned 8 bit integer is returned - this is the data received.

Definition at line 227 of file usart.c.

{
  char hundreds = '0';
  char tens = '0';
  char ones = '0';
  char thisChar = '0';
  do
  {
    hundreds = tens;
    tens = ones;
    ones = thisChar;
    thisChar = receive_byte(); // get a new character
    transmit_byte(thisChar);   // echo
  }
  while (thisChar != '\r'); // until type return
 
  // TODO: Bracketise this further
  return (100 * (hundreds - '0') + 10 * (tens - '0') + ones - '0');
}