pentabug/firmware/lib/usart.c

/*
 * PentaFnord Firmware
 *
 * by Alexander Lorz <bigalex@gmx.de>
 *
 *
 * The USART control code is derived by code from the 4CHLED project
 * by sebseb7: https://github.com/sebseb7/eagle/tree/master/4CHLED/firmware
 *
 * This program is free software: you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 3 as published by
 * the Free Software Foundation.
 *
 * This program 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
 * this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <avr/io.h>
#include <avr/interrupt.h>

#include "usart.h"

#define UART_RXBUFSIZE 32

static volatile uint8_t rxbuf0[UART_RXBUFSIZE];
static volatile uint8_t * volatile rxhead0, * volatile rxtail0;


ISR (USART_RX_vect) {
	UCSR0B &= ~(1 << RXCIE0);
	asm volatile("sei");

	int diff;
	uint8_t c;
	c = UDR0;
	diff = rxhead0 - rxtail0;
	if (diff < 0)
		diff += UART_RXBUFSIZE;
	if (diff < UART_RXBUFSIZE - 1) {
		*rxhead0 = c;
		++rxhead0;
		if (rxhead0 == (rxbuf0 + UART_RXBUFSIZE))
			rxhead0 = rxbuf0;

	}
	UCSR0B |= (1 << RXCIE0);
}

void USART0_Init(void) {
	// set baudrate
#define 	BAUD_TOL   4
#undef 		BAUD
#define 	BAUD 115200
#include <util/setbaud.h>
	UBRR0H = UBRRH_VALUE;
	UBRR0L = UBRRL_VALUE;

#if USE_2X
	UCSR0A |= (1 << U2X0); // enable double speed operation
#else
	UCSR0A &= ~(1 << U2X0); // disable double speed operation
#endif

	// flush receive buffer
	while (UCSR0A & (1 << RXC0))
		UDR0;

	// set 8N1
	UCSR0C = (1 << UCSZ01) | (1 << UCSZ00);
	UCSR0B &= ~(1 << UCSZ02);

	UCSR0B |= (1 << RXEN0) | (1 << TXEN0); //enable send and receive

	UCSR0B |= (1 << RXCIE0); //enable receive interrup

	rxhead0 = rxtail0 = rxbuf0;

}

void USART0_putc(char c) {
	loop_until_bit_is_set(UCSR0A, UDRE0);
	UDR0 = c;
}

uint8_t USART0_Getc_nb(uint8_t *c) {
	if (rxhead0 == rxtail0)
		return 0;
	*c = *rxtail0;
	if (++rxtail0 == (rxbuf0 + UART_RXBUFSIZE))
		rxtail0 = rxbuf0;
	return 1;
}

void USART0_crlf(void) {
	USART0_putc(0x0A); //newline
	USART0_putc(0x0D); //carriage return
}
;

void USART0_put_uint8(uint8_t x) {
	uint8_t highchar = ((x & 0b11110000) >> 4) + 0x30;
	uint8_t lowchar = (x & 0b00001111) + 0x30;
	highchar = highchar > 0x39 ? highchar + 0x07 : highchar; //chars A to F start with 0x41 not 0x3A
	lowchar = lowchar > 0x39 ? lowchar + 0x07 : lowchar;
	USART0_putc(highchar);
	USART0_putc(lowchar);

}
void USART0_put_uint16(uint16_t x) {
	USART0_put_uint8((x & 0xFF00) >> 8);
	USART0_put_uint8(x & 0x00FF);

}