AVR_ATMEGA_USART/avr_usart.c

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/*
* Author: Jake Goodwin
* Date: 2023
* Description: Small library to communicate with the AT-09 bluetooth module.
*/
#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>
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#include <stdint.h>
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#include <util/delay.h>
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#include "avr_usart.h"
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//#############################
//Globals
//#############################
int main() {
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led_blink();
led_blink();
led_blink();
_delay_ms(1000);
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_delay_ms(1000);
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init_usart0();
//enable interrupts
sei();
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uint8_t buf_len = 12;
//unsigned char data[12] = "snd 12chars\0";
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//unsigned char data[1] = "A";
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unsigned char data[1] = "B";
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while(1) {
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//serial0_write(data, buf_len);
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if(data[0] == 0) {
data[0] = '!';
}
tx_usart0(data[0]);
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//serial0_read(data, buf_len);
//data = rx_usart0();
serial0_flush_rxbuf();
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serial0_read_with_err_checking(data, 1);
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}
return 0;
}
//#############################
//FUNCTIONS
//#############################
/*
* Input: None
* Output: None
* Description: init usart0 hardware in async mode
*/
void init_usart0(void) {
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//DDRB |= (1<<TX_DDR)|(0<<RX_DDR);
//PORTD |= (0<<TX_PIN)|(0<<RX_PIN);
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//setup stuff for usart communications.
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//set baud rate, this is 9600Baud with a 8Mhz clock
//UBRR0H |= (uint8_t) (BT_UBRR>>8);
//UBRR0L |= (uint8_t) BT_UBRR;
UBRR0H |= (uint8_t) (0x33>>8);
UBRR0L |= (uint8_t) 0x33;
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//Enable recv and Transmit pins, overrides other uses.
//IN the usart control and status register 0B
UCSR0B = (1<<RXEN0) | (1<<TXEN0);
//setting the data frame format
//We leave the 2MSB zero for async serial. And we also don't enable
//parity bits for now. We set a 2bit stop bit and 8bit char size.
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//UCSR0C = (1<<USBS0) | (3<<UCSZ00);
UCSR0C = (1<<USBS0) | (1<<UCSZ00) | (1<<UCSZ01) | (0<<UCSZ02);
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}
/*
* Input: a 8bit char
* Output: None
* Description: Sends a char over usart0
*/
void tx_usart0(unsigned char data) {
//first wait for the transmit buffer to be empty
while(!(UCSR0A & (1<<UDRE0))) {
;//Equiv of continue
}
//now that it's empty, fill buffer with TX data.
UDR0 = data;
}
/*
* Input:None
* Output: a 8bit char
* Description: Recvs a char over usart0
*/
unsigned char rx_usart0(void) {
//first wait for the data to be received.
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while( !(UCSR0A & (1<<RXC0)) ) {
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;//Equiv of continue
}
//now return the data
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return UDR0;
}
void serial0_flush_rxbuf(void) {
uint8_t none;
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while( UCSR0A & (1<<RXC0)) {
none = UDR0;
}
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}
/*
* Inupt: None
* Output: None
* Description: Nothing right now.
*/
void serial0_enable_timeouts(uint8_t ms) {
;
}
/*
* Inupt: None
* Output: None
* Description:
*/
void serial0_write(unsigned char* buffer, uint8_t write_length) {
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for(uint8_t i = 0; i < write_length; i++) {
tx_usart0(buffer[i]);
}
}
/*
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* Inupt: A serialbuffer and length
* Output: None
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* Description: Reads the serial data into a buffer of x length.
*/
void serial0_read(unsigned char* buffer, uint8_t buf_length) {
//clear buffer out?
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//buffer = 0;
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for(uint8_t i = 0; i < buf_length; i++) {
buffer[i] = rx_usart0();
}
}
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/*
* Inupt: A serialbuffer and length
* Output: None
* Description: Reads the serial data into a buffer of x length,
* it does error checking from the register first.
*/
void serial0_read_with_err_checking(unsigned char* buffer, uint8_t buf_length) {
//first wait for the data to be received.
while( !(UCSR0A & (1<<RXC0)) ) {
;//Equiv of continue
}
//check for errors in the register.
//Check for frame error.
if(UCSR0A & (1<<FE0)) {
led_blink();
}
//check for data over-run
else if(UCSR0A & (1<<DOR0)) {
led_blink();
led_blink();
}
//check for parity error
else if(UCSR0A & (1<<UPE0)) {
led_blink();
led_blink();
led_blink();
}
//now return the data
buffer[0] = UDR0;
}
/*
* Inupt: BUAD RATE as uint8_t
* Output: None
* Description: Sets the baud rate of the serial usart0
* VALUES @ 1Mhz:
* 207 --> 300bps
* 103 --> 600bps
* 51 --> 1200bps
* 25 --> 2400bps
* 12 --> 4800bps
* 6 --> 9600bps !!! 7% error rate
*/
void serial0_set_baud(uint8_t baud) {
UBRR0H |= (uint8_t) (baud>>8);
UBRR0L |= (uint8_t) baud;
}
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/*
* Input: None
* Output: None
* Description: Toggles the pin for the LED indicator.
*/
static void led_blink(void) {
//Set the DDR for output.
DDRC |= (1<<LED_PIN);
PORTC ^= (1<<LED_PIN);
_delay_ms(250);
PORTC ^= (1<<LED_PIN);
_delay_ms(250);
}