usart_atmega

usart library for the atmega328p for embedded systems programming using embedded C and avr-gcc

Still in development

The following is a list of features still to be implemented into the library:

• ODR (output data rate) flag for baud rate control
• Resolve issue with F_CPU macro conflict
• Add interrupt support handlers
• Add usart number flag to select which usart to use (if more that usart 0 is available on microcontroller)
• add read functions (unfortunately missed this in first pass 🫣)

makefile Suggestions

A possible way of including this library to projects are to git clone the repository to a libs directory in the project directory. Then you can either generate a shell script to iterate through all project folders to call make or make a explicit rule in your project makefile. make -C other_makefile_dir the command above will run make in the provided directory.

Disclaimer

Currently the library requires the manual definition of F_CPU macro in usart.h. This macro is also used by the avr-libc for functions like _delay_ms()

type definitions

usart_mode_t

USART_MODE_ASYNC

Asynchronous communication (UART)

USART_MODE_SYNC

Synchronous communication (USRT)

usart_stop_bit_t

USART_STOP_BIT_1

Sets the frame to use 1 stop bit

USART_STOP_BIT_2

Sets the frame to use 2 stop bits

usart_parity_t

USART_PARITY_OFF

Disables parity checking on frame transmission

USART_PARITY_EVEN

Sets parity on and enables even parity

USART_PARITY_ODD

Sets parity on and enables odd parity

usart_config_t

Struct that hold the desired usart configuration data.

data member name	description
usart_num	The index number of target usart
baudrate	the desired baudrate of the usart communication
usart_mode	the desired mode of communication async or sync (refer to usart modes for macro options)
frame_size	the number of bits per frame transmission (accepts values where 5 <= frameSize <= 9 as uint8_t)
stop_bits	the number of stopBits per frame transmission (refer to stop bit options for macro options)
parity_mode	enable/disable parity for usart transmission (refer to parity modes for macro options)

usart_config_ptr

pointer to usart_config_t

Functions

uint8_t usart_calc_baud(uint8_t usart_num, uint16_t baudrate)

Function that calculates the UDDRn value required to achieve desired baudrate. (Disclaimer currently requires manual setting of U2Xn)

void usart_set_baud(uint8_t usart_num, uint16_t baudrate)

Function to the baudrate of target usart

void usart_set_frame_size(uint8_t usart_num, uint8_t frame_size)

Function to set frame size of target usart

void usart_set_mode(uint8_t usart_num, usart_mode_t mode)

Function to set the mode of target usart.

void usart_set_parity(uint8_t usart_num, usart_parity_t parity)

Function to set the parity of target usart

void usart_set_stopbits(uint8_t usart_num, usart_stop_bit_t stop_bits)

Function to set the stop bits of target usart

void usart_init(usart_config_ptr config_data)

function that initialises the usart using the usart_config_t data passed

usart_sendChar(uint8_t usart_num, char c)

Function to send a single character of the usart bus

usart_sentString(uint8_t usart_num, char* string)

Function to send a string over the usart bus