121 lines
3.2 KiB
C
121 lines
3.2 KiB
C
/*
|
|
serial.c - Low level functions for sending and recieving bytes via the serial port
|
|
Part of Grbl
|
|
|
|
Copyright (c) 2009-2011 Simen Svale Skogsrud
|
|
|
|
Grbl is free software: you can redistribute it and/or modify
|
|
it under the terms of the GNU General Public License as published by
|
|
the Free Software Foundation, either version 3 of the License, or
|
|
(at your option) any later version.
|
|
|
|
Grbl is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
GNU General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with Grbl. If not, see <http://www.gnu.org/licenses/>.
|
|
*/
|
|
|
|
/* This code was initially inspired by the wiring_serial module by David A. Mellis which
|
|
used to be a part of the Arduino project. */
|
|
|
|
#include <avr/interrupt.h>
|
|
#include <avr/sleep.h>
|
|
|
|
|
|
#ifdef __AVR_ATmega328P__
|
|
#define RX_BUFFER_SIZE 256
|
|
#else
|
|
#define RX_BUFFER_SIZE 64
|
|
#endif
|
|
|
|
#define TX_BUFFER_SIZE 16
|
|
|
|
uint8_t rx_buffer[RX_BUFFER_SIZE];
|
|
uint8_t rx_buffer_head = 0;
|
|
uint8_t rx_buffer_tail = 0;
|
|
|
|
uint8_t tx_buffer[TX_BUFFER_SIZE];
|
|
uint8_t tx_buffer_head = 0;
|
|
volatile uint8_t tx_buffer_tail = 0;
|
|
|
|
|
|
void serial_init(long baud)
|
|
{
|
|
UBRR0H = ((F_CPU / 16 + baud / 2) / baud - 1) >> 8;
|
|
UBRR0L = ((F_CPU / 16 + baud / 2) / baud - 1);
|
|
|
|
/* baud doubler off - Only needed on Uno XXX */
|
|
UCSR0A &= ~(1 << U2X0);
|
|
|
|
// enable rx and tx
|
|
UCSR0B |= 1<<RXEN0;
|
|
UCSR0B |= 1<<TXEN0;
|
|
|
|
// enable interrupt on complete reception of a byte
|
|
UCSR0B |= 1<<RXCIE0;
|
|
|
|
// defaults to 8-bit, no parity, 1 stop bit
|
|
}
|
|
|
|
void serial_write(uint8_t data) {
|
|
// Calculate next head
|
|
uint8_t next_head = (tx_buffer_head + 1) % TX_BUFFER_SIZE;
|
|
|
|
// Wait until there's a space in the buffer
|
|
while (next_head == tx_buffer_tail) { sleep_mode(); };
|
|
|
|
// Store data and advance head
|
|
tx_buffer[tx_buffer_head] = data;
|
|
tx_buffer_head = next_head;
|
|
|
|
// Enable Data Register Empty Interrupt
|
|
UCSR0B |= (1 << UDRIE0);
|
|
}
|
|
|
|
// Data Register Empty Interrupt handler
|
|
SIGNAL(USART_UDRE_vect) {
|
|
|
|
// temporary tx_buffer_tail (to optimize for volatile)
|
|
uint8_t tail = tx_buffer_tail;
|
|
|
|
// Send a byte from the buffer
|
|
UDR0 = tx_buffer[tail];
|
|
|
|
// Update tail position
|
|
tail ++;
|
|
tail %= TX_BUFFER_SIZE;
|
|
tx_buffer_tail = tail;
|
|
|
|
// Turn off Data Register Empty Interrupt if this concludes the transfer
|
|
if (tail == tx_buffer_head) { UCSR0B &= ~(1 << UDRIE0); }
|
|
}
|
|
|
|
uint8_t serial_read()
|
|
{
|
|
if (rx_buffer_head != rx_buffer_tail) {
|
|
return 0xff;
|
|
} else {
|
|
uint8_t data = rx_buffer[rx_buffer_tail];
|
|
rx_buffer_tail = (rx_buffer_tail + 1) % RX_BUFFER_SIZE;
|
|
return data;
|
|
}
|
|
}
|
|
|
|
SIGNAL(USART_RX_vect)
|
|
{
|
|
uint8_t data = UDR0;
|
|
uint8_t next_head = (rx_buffer_head + 1) % RX_BUFFER_SIZE;
|
|
|
|
// if we should be storing the received character into the location
|
|
// just before the tail (meaning that the head would advance to the
|
|
// current location of the tail), we're about to overflow the buffer
|
|
// and so we don't write the character or advance the head.
|
|
if (next_head != rx_buffer_tail) {
|
|
rx_buffer[rx_buffer_head] = data;
|
|
rx_buffer_head = next_head;
|
|
}
|
|
}
|