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#include "SafeSerial.h"
#include <avr/interrupt.h>
typedef struct {
uint8_t buffer[SERIAL_BUFFER_SIZE];
volatile uint16_t head;
volatile uint16_t tail;
} ring_buffer;
static ring_buffer tx_buffer = {{0}, 0, 0};
SafeSerial::begin(uint32_t baud) {
//enable double speed transmission
*ucsrXa |= (1 << u2xX);
uint16_t baudSetting = (F_CPU / 4 / baud - 1) / 2;
// assign the baud_setting, a.k.a. ubbr (USART Baud Rate Register)
*ubrrXh = baudSetting >> 8;
*ubrrXl = baudSetting;
// defaults to 8-bit, no parity, 1 stop bit
*ucsrXb |= (1 << *exenX) | (1 << *txenX) | (1 << *rxcieX);
*ucsrXb &= ~(1 << *udrieX) | (1 << *txenX) | (1 << *rxcieX);
}
//receive
ISR(USART0_RX_vect) {
uint8_t c = UDR0;
serial.put(c);
}
//data register empty
ISR(USART0_UDRE_vect) {
if (tx_buffer.head == tx_buffer.tail) {
//buffer empty, disable interruot
UCSR0B &= ~(1 << UDRIE0);
} else {
uint8_t c = tx_buffer.buffer[tx_buffer.tail];
tx_buffer.tail = (tx_buffer.tail + 1) % SERIAL_BUFFER_SIZE;
UDR0 = c; //write next byte
}
}
void SafeSerial::send(uint8_t byte) {
uint16_t i = (tx_buffer.head + 1) % SERIAL_BUFFER_SIZE;
// If the output buffer is full, there's nothing for it other than to
// wait for the interrupt handler to empty it a bit
if (i == tx_buffer.tail) return;
//while (i == tx_buffer.tail) {};
tx_buffer.buffer[tx_buffer.head] = byte;
tx_buffer.head = i;
//enable data register empty interrupt
UCSR0B |= (1 << UDRIE0);
};
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