Moving hardware/targets to hardware/cores.

1 files changed, 196 insertions, 0 deletions

diff --git a/cores/arduino/wiring.c b/cores/arduino/wiring.c
new file mode 100755
index 0000000..5dda822
--- /dev/null
+++ b/cores/arduino/wiring.c
@@ -0,0 +1,196 @@
+/*
+  wiring.c - Partial implementation of the Wiring API for the ATmega8.
+  Part of Arduino - http://www.arduino.cc/
+
+  Copyright (c) 2005-2006 David A. Mellis
+
+  This library is free software; you can redistribute it and/or
+  modify it under the terms of the GNU Lesser General Public
+  License as published by the Free Software Foundation; either
+  version 2.1 of the License, or (at your option) any later version.
+
+  This library 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
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General
+  Public License along with this library; if not, write to the
+  Free Software Foundation, Inc., 59 Temple Place, Suite 330,
+  Boston, MA  02111-1307  USA
+
+  $Id$
+*/
+
+#include "wiring_private.h"
+
+// The number of times timer 0 has overflowed since the program started.
+// Must be volatile or gcc will optimize away some uses of it.
+volatile unsigned long timer0_overflow_count;
+
+SIGNAL(SIG_OVERFLOW0)
+{
+	timer0_overflow_count++;
+}
+
+unsigned long millis()
+{
+	// timer 0 increments every 64 cycles, and overflows when it reaches
+	// 256.  we would calculate the total number of clock cycles, then
+	// divide by the number of clock cycles per millisecond, but this
+	// overflows too often.
+	//return timer0_overflow_count * 64UL * 256UL / (F_CPU / 1000UL);
+	
+	// instead find 1/128th the number of clock cycles and divide by
+	// 1/128th the number of clock cycles per millisecond
+	return timer0_overflow_count * 64UL * 2UL / (F_CPU / 128000UL);
+}
+
+void delay(unsigned long ms)
+{
+	unsigned long start = millis();
+	
+	while (millis() - start < ms)
+		;
+}
+
+/* Delay for the given number of microseconds.  Assumes a 16 MHz clock. 
+ * Disables interrupts, which will disrupt the millis() function if used
+ * too frequently. */
+void delayMicroseconds(unsigned int us)
+{
+	uint8_t oldSREG;
+
+	// calling avrlib's delay_us() function with low values (e.g. 1 or
+	// 2 microseconds) gives delays longer than desired.
+	//delay_us(us);
+
+#if F_CPU >= 16000000L
+    // for the 16 MHz clock on most Arduino boards
+
+	// for a one-microsecond delay, simply return.  the overhead
+	// of the function call yields a delay of approximately 1 1/8 us.
+	if (--us == 0)
+		return;
+
+	// the following loop takes a quarter of a microsecond (4 cycles)
+	// per iteration, so execute it four times for each microsecond of
+	// delay requested.
+	us <<= 2;
+
+	// account for the time taken in the preceeding commands.
+	us -= 2;
+#else
+    // for the 8 MHz internal clock on the ATmega168
+
+    // for a one- or two-microsecond delay, simply return.  the overhead of
+    // the function calls takes more than two microseconds.  can't just
+    // subtract two, since us is unsigned; we'd overflow.
+	if (--us == 0)
+		return;
+	if (--us == 0)
+		return;
+
+	// the following loop takes half of a microsecond (4 cycles)
+	// per iteration, so execute it twice for each microsecond of
+	// delay requested.
+	us <<= 1;
+    
+    // partially compensate for the time taken by the preceeding commands.
+    // we can't subtract any more than this or we'd overflow w/ small delays.
+    us--;
+#endif
+
+	// disable interrupts, otherwise the timer 0 overflow interrupt that
+	// tracks milliseconds will make us delay longer than we want.
+	oldSREG = SREG;
+	cli();
+
+	// busy wait
+	__asm__ __volatile__ (
+		"1: sbiw %0,1" "\n\t" // 2 cycles
+		"brne 1b" : "=w" (us) : "0" (us) // 2 cycles
+	);
+
+	// reenable interrupts.
+	SREG = oldSREG;
+}
+
+void init()
+{
+	// this needs to be called before setup() or some functions won't
+	// work there
+	sei();
+	
+	// timer 0 is used for millis() and delay()
+	timer0_overflow_count = 0;
+	// on the ATmega168, timer 0 is also used for fast hardware pwm
+	// (using phase-correct PWM would mean that timer 0 overflowed half as often
+	// resulting in different millis() behavior on the ATmega8 and ATmega168)
+#if defined(__AVR_ATmega168__)
+	sbi(TCCR0A, WGM01);
+	sbi(TCCR0A, WGM00);
+#endif  
+	// set timer 0 prescale factor to 64
+#if defined(__AVR_ATmega168__)
+	sbi(TCCR0B, CS01);
+	sbi(TCCR0B, CS00);
+#else
+	sbi(TCCR0, CS01);
+	sbi(TCCR0, CS00);
+#endif
+	// enable timer 0 overflow interrupt
+#if defined(__AVR_ATmega168__)
+	sbi(TIMSK0, TOIE0);
+#else
+	sbi(TIMSK, TOIE0);
+#endif
+
+	// timers 1 and 2 are used for phase-correct hardware pwm
+	// this is better for motors as it ensures an even waveform
+	// note, however, that fast pwm mode can achieve a frequency of up
+	// 8 MHz (with a 16 MHz clock) at 50% duty cycle
+
+	// set timer 1 prescale factor to 64
+	sbi(TCCR1B, CS11);
+	sbi(TCCR1B, CS10);
+	// put timer 1 in 8-bit phase correct pwm mode
+	sbi(TCCR1A, WGM10);
+
+	// set timer 2 prescale factor to 64
+#if defined(__AVR_ATmega168__)
+	sbi(TCCR2B, CS22);
+#else
+	sbi(TCCR2, CS22);
+#endif
+	// configure timer 2 for phase correct pwm (8-bit)
+#if defined(__AVR_ATmega168__)
+	sbi(TCCR2A, WGM20);
+#else
+	sbi(TCCR2, WGM20);
+#endif
+
+	// set a2d reference to AVCC (5 volts)
+	cbi(ADMUX, REFS1);
+	sbi(ADMUX, REFS0);
+
+	// set a2d prescale factor to 128
+	// 16 MHz / 128 = 125 KHz, inside the desired 50-200 KHz range.
+	// XXX: this will not work properly for other clock speeds, and
+	// this code should use F_CPU to determine the prescale factor.
+	sbi(ADCSRA, ADPS2);
+	sbi(ADCSRA, ADPS1);
+	sbi(ADCSRA, ADPS0);
+
+	// enable a2d conversions
+	sbi(ADCSRA, ADEN);
+
+	// the bootloader connects pins 0 and 1 to the USART; disconnect them
+	// here so they can be used as normal digital i/o; they will be
+	// reconnected in Serial.begin()
+#if defined(__AVR_ATmega168__)
+	UCSR0B = 0;
+#else
+	UCSRB = 0;
+#endif
+}
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