kopia lustrzana https://github.com/fsphil/hadie
102 wiersze
2.3 KiB
C
102 wiersze
2.3 KiB
C
/* hadie - High Altitude Balloon flight software */
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/*============================================================*/
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/* Copyright (C)2010 Philip Heron <phil@sanslogic.co.uk> */
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/* */
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/* This program is distributed under the terms of the GNU */
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/* General Public License, version 2. You may use, modify, */
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/* and redistribute it under the terms of this license. A */
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/* copy should be included with this source. */
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#include "config.h"
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#include <avr/io.h>
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#include <util/delay.h>
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#include <avr/interrupt.h>
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#include <avr/pgmspace.h>
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#include <string.h>
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#include "rtty.h"
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/* MARK = Upper tone, Idle, bit */
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#define TXENABLE (0x04)
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#define MARK (0x02)
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#define SPACE (0x01)
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#define TXBIT(b) PORTB = (PORTB & ~(MARK | SPACE)) | (b)
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volatile uint8_t txpgm = 0;
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volatile uint8_t *txbuf = 0;
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volatile uint16_t txlen = 0;
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ISR(TIMER0_COMPA_vect)
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{
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/* The currently transmitting byte, including framing */
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static uint8_t byte = 0x00;
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static uint8_t bit = 0x00;
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uint8_t b = 0;
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switch(bit++)
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{
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case 0: b = 0; break; /* Start bit */
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case 9: b = 1; break; /* Stop bit */
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case 10: b = 1; TCNT0 += OCR0A >> 1; bit = 0; break; /* Stop bit 0.5 */
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default: b = byte & 1; byte >>= 1; break;
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}
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TXBIT(b ? MARK : SPACE);
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if(bit == 0 && txlen > 0)
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{
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if(txpgm == 0) byte = *(txbuf++);
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else byte = pgm_read_byte(txbuf++);
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txlen--;
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}
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}
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void rtx_init()
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{
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/* RTTY is driven by TIMER0 in CTC mode */
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TCCR0A = _BV(WGM01); /* Mode 2, CTC */
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TCCR0B = _BV(CS02) | _BV(CS00); /* prescaler 1024 */
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OCR0A = F_CPU / 1024 / RTTY_BAUD;
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TIMSK0 = _BV(OCIE0A); /* Enable interrupt */
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/* We use Port B pins 1, 2 and 3 */
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TXBIT(MARK);
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PORTB |= TXENABLE;
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DDRB |= MARK | SPACE | TXENABLE;
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}
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void inline rtx_wait()
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{
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/* Wait for interrupt driven TX to finish */
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while(txlen > 0) while(txlen > 0);
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}
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void rtx_data(uint8_t *data, size_t length)
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{
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rtx_wait();
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txpgm = 0;
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txbuf = data;
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txlen = length;
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}
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void rtx_data_P(PGM_P data, size_t length)
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{
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rtx_wait();
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txpgm = 1;
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txbuf = (uint8_t *) data;
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txlen = length;
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}
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void rtx_string(char *s)
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{
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uint16_t length = strlen(s);
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rtx_data((uint8_t *) s, length);
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}
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void rtx_string_P(PGM_P s)
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{
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uint16_t length = strlen_P(s);
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rtx_data_P(s, length);
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}
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