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/*
* AE6HO EZ-Doppler firmware for onboard ATmega8 microcontroller
* Copyright 2006 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
* GNU Radio 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 2, or (at your option)
* any later version.
*
* GNU Radio 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 GNU Radio; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
/*
* ARCHITECTURE
*
* Timer0 is 8000 Hz time base
* PORTD.2 through PORTD.5 are doppler antenna array element enables.
* PORTB.0 is a diagnostic LED, set low to light up
* ADC7 is audio input
* ADC6 is RSSI input - not yet used
*
*/
#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/signal.h>
#include "dopctrl.h"
#define LED 0
#define turn_off_led() PORTB |= _BV(LED);
#define turn_on_led() PORTB &= ~_BV(LED);
#define ANT1 _BV(2)
#define ANT2 _BV(3)
#define ANT3 _BV(4)
#define ANT4 _BV(5)
#define ANTMASK ANT1|ANT2|ANT3|ANT4
#define ADCAIN 7
#define BAUDRATE 250000
/* Assume these are all set to zero in startup code */
uint8_t rotate; /* Flag to indicate antennas should rotate or not */
uint8_t streaming; /* Flag to indicate continuous sampling */
uint8_t antennas; /* Holds shadow copy of PORTD antennas */
uint8_t speed; /* Holds samples per phase increment */
uint8_t phase; /* Holds rotation phase (measured in samples */
uint8_t audio_hi; /* High byte of ADC sample of audio */
uint8_t audio_lo; /* Low byte of ADC sample of audio */
uint8_t rx; /* Temporary holds received byte from USART */
uint8_t command; /* Temporary to hold command when getting operand */
uint8_t cmdbyte; /* Tracks bytes received in multi-byte commands */
int main(void)
{
/* Diagnostic port setup */
DDRB = _BV(LED); /* PB0 is output */
turn_off_led();
/* Antenna control port setup */
speed = 4; /* Todo: read from EEPROM */
antennas = ANT1; /* Start with antenna #1 */
PORTD = antennas; /* Set port value */
DDRD = ANTMASK; /* Set antenna enables as PORTD outputs */
/* ADC port setup */
ADMUX = _BV(REFS0)|ADCAIN; /* AVCC is reference, use ADC for audio input (ADC7) */
ADCSRA = _BV(ADEN)|_BV(ADIE)|0x07; /* Enable converter, prescale by 128, enable ADC interrupt */
/* USART port setup*/
UCSRA = 0; /* Normal asynchronous mode */
UCSRB = _BV(TXEN)|_BV(RXEN)|_BV(RXCIE); /* Enable transmitter and receiver, and receiver interrupts */
UCSRC = _BV(URSEL)|_BV(UCSZ1)|_BV(UCSZ0); /* 8N1 format */
UBRRH = 0; /* Set baud rate prescaler to 3 */
UBRRL = 3; /* To get 250000 bps */
/* Set up 8000 Hz time base */
timer_enable_int(_BV(TOIE0)); /* Turn on Timer0 output overflow interrupt */
TCCR0 = _BV(CS01); /* Clock Timer0 from CLK/8 */
sei(); /* Let 'er rip! */
return 0;
}
/* Timer0 overflow interrupt handler
*
* Creates 8000 Hz time base, or 125us budget
*
*/
SIGNAL(SIG_OVERFLOW0)
{
/* Reload Timer0 samples to 8, results in 8000 Hz overflow interrupt */
TCNT0 = 0x08;
if (streaming) {
/* Kick-off an audio sample conversion, will interrupt 104us later */
ADCSRA |= _BV(ADSC);
/* Write the first byte of previous sample and enable UDRIE */
UDR = audio_lo;
UCSRB |= _BV(UDRIE);
}
if (!rotate) /* Skip rotating antenna if not started */
return;
/* Increment antenna phase and see if antenna need to be rotated */
if (++phase == speed) {
phase = 0;
/* Sequence antenna array elements */
antennas >>= 1;
antennas &= ANTMASK;
if (!antennas)
antennas = ANT4;
PORTD = antennas;
}
}
/* ADC conversion complete interrupt handler
*
* Read value and store. Assume prior sample has been handled.
*
*/
SIGNAL(SIG_ADC)
{
audio_lo = ADCL;
audio_hi = ADCH;
}
/* USART data transmit holding register empty interrupt handler
*
* First byte is always sent from timer interrupt
* So second byte gets sent here with UDRIE disabled
*
*/
SIGNAL(SIG_UART_DATA)
{
/* Write second byte of previous sample and disable UDRIE */
UDR = audio_hi | (antennas << 2);
UCSRB &= ~_BV(UDRIE);
}
/* USART receive complete interrupt handler
*
* Received bytes are commands, with one or two bytes of operands following
*
*/
SIGNAL(SIG_UART_RECV)
{
rx = UDR;
if (cmdbyte == 0) {
if (rx == EZDOP_CMD_ROTATE) /* Start rotation */
rotate = 1;
else if (rx == EZDOP_CMD_STOP) /* Stop rotation */
rotate = 0;
else if (rx == EZDOP_CMD_RATE) { /* Set rotation rate */
command = rx;
cmdbyte = 1;
}
else if (rx == EZDOP_CMD_STREAM) /* Stream audio samples */
streaming = 1;
else if (rx == EZDOP_CMD_STROFF) /* Stop streaming */
streaming = 0;
else
turn_on_led(); /* Unknown command */
}
else if (cmdbyte == 1) {
if (command == EZDOP_CMD_RATE) { /* Operand is number of samples per phase increment */
speed = rx;
cmdbyte = 0;
}
else
turn_on_led(); /* Bogus command state */
}
else
turn_on_led(); /* Bogus command state */
}
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