EmbeddedSystems/EmbeddedSystemsTHM/UART.c

145 lines
3.8 KiB
C

/*
* UART.c
*
* Created: 25/11/2021 16:26:10
* Author: n0x
*/
#include "UART.h"
/* create structs for TX and TX buffer */
CircularBuffer TxBuffer;
CircularBuffer* pTxBuffer = &TxBuffer;
CircularBuffer RxBuffer;
CircularBuffer* pRxBuffer = &RxBuffer;
volatile uint8_t TxActive;
void
uart_init(void) {
UBRR0 = 103; /* set BAUD rate to 9600 */
UCSR0C |=
(0<<UMSEL00)|(0<<UMSEL01)| /* Async UART */
(0<<UPM00)|(0<<UPM01)| /* Disable Parity */
(1<<UCSZ00)|(1<<UCSZ01)| /* 8 Bit */
(0<<USBS0); /* 1 Stopbit */
UCSR0B |=
(1<<TXEN0)|(1<<RXEN0)| /* enable send and receive */
(1<<RXCIE0); /* enable Receive interrupts */
/* Initiate read- and write-pointers with 0 */
pTxBuffer->Readpointer = 0;
pTxBuffer->Writepointer = 0;
pRxBuffer->Readpointer = 0;
pRxBuffer->Writepointer = 0;
}
/********Sending Data********/
void
uart_send_string(char* string) {
/* Take a whole string and transmit every char from it */
int i = 0;
while(string[i] != '\0'){
uart_send_byte(string[i]);
i++;
}
}
void
uart_send_byte(char c) {
/* Disable the TX Interrupt to prevent issues while writing to the send buffer*/
UCSR0B &= ~(1<<TXCIE0);
/* Check if a transmit is in progress
if yes -> write the byte to the buffer
if no -> write the byte to the UDR0 register and enable the transmit in progress flag
*/
if(TxActive){
pTxBuffer->data[pTxBuffer->Writepointer++] = c;
if (pTxBuffer->Writepointer>=SIZE_BUFFER){
pTxBuffer->Writepointer = 0;
}
} else {
TxActive = 1;
UDR0 = c;
}
/* Enable the TX Interrupt again*/
UCSR0B |= (1<<TXCIE0);
}
/* when data (a data frame) is to be send (written to UDR0) */
ISR(USART0_TX_vect) {
/* check if the read and write pointer of the send buffer are not aligned
if not aligned -> read the next byte and write it to UDR0 register
if aligned -> no more data to send, disable the send in progress flag */
if(pTxBuffer->Readpointer != pTxBuffer->Writepointer)
{
/* writing data to the register withing the interrupt will cause a new interrupt which then will repeat till no more data is to be read from the send buffer */
UDR0 = pTxBuffer->data[pTxBuffer->Readpointer++];
if(pTxBuffer->Readpointer >= SIZE_BUFFER){
pTxBuffer->Readpointer = 0;
}
} else {
TxActive = 0;
}
}
/*******Receiving Data*******/
uint8_t
uart_data_available(void) {
uint8_t dataAvailabel = 0;
/* Disable the RX Interrupt to prevent issues when checking if data is available */
UCSR0B &= ~(1<<RXCIE0);
/* check if read and write pointer are at different locations
if yes -> data is available and can be read */
if(pRxBuffer->Readpointer != pRxBuffer->Writepointer){
dataAvailabel = 1;
}
/* Enable the RX Interrupt again*/
UCSR0B |= (1<<RXCIE0);
return dataAvailabel;
}
char
uart_get_data(void) {
char data = 0;
/* Disable the RX Interrupt to prevent issues when reading out a char from the buffer */
UCSR0B &= ~(1<<RXCIE0);
/* check if read and write pointer are at different locations
if yes -> data is available and can be read */
if(pRxBuffer->Readpointer != pRxBuffer->Writepointer)
{
/* read a char from the buffer and increment the read pointer */
data = pRxBuffer->data[pRxBuffer->Readpointer++];
if(pRxBuffer->Readpointer >= SIZE_BUFFER){
pRxBuffer->Readpointer = 0;
}
}
/* Enable the RX Interrupt again*/
UCSR0B |= (1<<RXCIE0);
/* give back the read in character */
return data;
}
/* when data (a data frame) is received */
ISR(USART0_RX_vect) {
uint8_t status = UCSR0A;
uint8_t data = UDR0;
/* check status flags if data is correctly accessible */
if((status & ((1<<DOR0) | (1<<FE0))) == 0){
/* Save data to buffer and increment the write pointer */
pRxBuffer->data[pRxBuffer->Writepointer++] = data;
if(pRxBuffer->Writepointer >= SIZE_BUFFER) {
pRxBuffer->Writepointer = 0;
}
}
}