usart.h File Reference

Driver file providing core USART communication between the target MCU and your PC. More...

#include <stdint.h>

Go to the source code of this file.

Macros
#define	BAUD   9600
#define	USART_HAS_DATA   bit_is_set(UCSR0A, RXC0)
#define	USART_READY   bit_is_set(UCSR0A, UDRE0)

Functions
void	init_usart (void)
	Takes the defined BAUD and F_CPU, calculates the bit-clock multiplier, configures the hardware USART. More...
void	print_string (const char myString[])
	Utility function to transmit an entire string from RAM. More...
void	read_string (char myString[], uint8_t maxLength)
	Define a string variable, pass it to this function. More...
void	print_byte (uint8_t byte)
	Prints a byte out as its 3-digit ascii equivalent. More...
void	print_word (uint16_t word)
	Prints a word (16-bits) out as its 5-digit ascii equivalent. More...
void	print_binary_byte (uint8_t byte)
	Prints a byte out in 1s and 0s. More...
char	nibble_to_hex (uint8_t nibble)
	Convert nibble to hex.
char	nibble_to_hex_character (uint8_t nibble)
	Convert nibble to hex character. More...
void	print_hex_byte (uint8_t byte)
	Prints a byte out in hexadecimal. More...
uint8_t	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.

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

Definition in file usart.h.

Macro Definition Documentation

BAUD

#define BAUD   9600

Definition at line 36 of file usart.h.

USART_HAS_DATA

#define USART_HAS_DATA   bit_is_set(UCSR0A, RXC0)

Definition at line 45 of file usart.h.

USART_READY

#define USART_READY   bit_is_set(UCSR0A, UDRE0)

Definition at line 46 of file usart.h.

Function Documentation

init_usart()

void init_usart

(

void

)

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

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);
}

print_string()

void print_string

(

const char

myString[]

)

Utility function to transmit an entire string from RAM.

Definition at line 67 of file usart.c.

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

read_string()

void read_string	(	char	myString[],
		uint8_t	maxLength
	)

Define a string variable, pass it to this function.

The string will contain whatever you typed over serial.

Definition at line 81 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 */
}

print_byte()

void print_byte

(

uint8_t

byte

)

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

Definition at line 106 of file usart.c.

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

print_word()

void print_word

(

uint16_t

word

)

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

Definition at line 115 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
}

print_binary_byte()

void print_binary_byte

(

uint8_t

byte

)

Prints a byte out in 1s and 0s.

Definition at line 125 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');
    }
  }
}

nibble_to_hex_character()

char nibble_to_hex_character

(

uint8_t

nibble

)

Convert nibble to hex character.

Definition at line 142 of file usart.c.

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

print_hex_byte()

void print_hex_byte

(

uint8_t

byte

)

Prints a byte out in hexadecimal.

Definition at line 155 of file usart.c.

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

get_number()

uint8_t get_number

(

void

)

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

Definition at line 165 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');
}