--- /dev/null
+/*
+ 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
+*/
+
+#include "wiring_private.h"
+
+// the prescaler is set so that timer0 ticks every 64 clock cycles, and the
+// the overflow handler is called every 256 ticks.
+#define MICROSECONDS_PER_TIMER0_OVERFLOW (clockCyclesToMicroseconds(64 * 256))
+
+// the whole number of milliseconds per timer0 overflow
+#define MILLIS_INC (MICROSECONDS_PER_TIMER0_OVERFLOW / 1000)
+
+// the fractional number of milliseconds per timer0 overflow. we shift right
+// by three to fit these numbers into a byte. (for the clock speeds we care
+// about - 8 and 16 MHz - this doesn't lose precision.)
+#define FRACT_INC ((MICROSECONDS_PER_TIMER0_OVERFLOW % 1000) >> 3)
+#define FRACT_MAX (1000 >> 3)
+
+volatile unsigned long timer0_overflow_count = 0;
+volatile unsigned long timer0_millis = 0;
+static unsigned char timer0_fract = 0;
+
+#if defined(TIM0_OVF_vect)
+ISR(TIM0_OVF_vect)
+#else
+ISR(TIMER0_OVF_vect)
+#endif
+{
+ // copy these to local variables so they can be stored in registers
+ // (volatile variables must be read from memory on every access)
+ unsigned long m = timer0_millis;
+ unsigned char f = timer0_fract;
+
+ m += MILLIS_INC;
+ f += FRACT_INC;
+ if (f >= FRACT_MAX) {
+ f -= FRACT_MAX;
+ m += 1;
+ }
+
+ timer0_fract = f;
+ timer0_millis = m;
+ timer0_overflow_count++;
+}
+
+unsigned long millis()
+{
+ unsigned long m;
+ uint8_t oldSREG = SREG;
+
+ // disable interrupts while we read timer0_millis or we might get an
+ // inconsistent value (e.g. in the middle of a write to timer0_millis)
+ cli();
+ m = timer0_millis;
+ SREG = oldSREG;
+
+ return m;
+}
+
+unsigned long micros() {
+ unsigned long m;
+ uint8_t oldSREG = SREG, t;
+
+ cli();
+ m = timer0_overflow_count;
+#if defined(TCNT0)
+ t = TCNT0;
+#elif defined(TCNT0L)
+ t = TCNT0L;
+#else
+ #error TIMER 0 not defined
+#endif
+
+#ifdef TIFR0
+ if ((TIFR0 & _BV(TOV0)) && (t < 255))
+ m++;
+#else
+ if ((TIFR & _BV(TOV0)) && (t < 255))
+ m++;
+#endif
+
+ SREG = oldSREG;
+
+ return ((m << 8) + t) * (64 / clockCyclesPerMicrosecond());
+}
+
+void delay(unsigned long ms)
+{
+ uint32_t start = micros();
+
+ while (ms > 0) {
+ yield();
+ while ( ms > 0 && (micros() - start) >= 1000) {
+ ms--;
+ start += 1000;
+ }
+ }
+}
+
+/* Delay for the given number of microseconds. Assumes a 1, 8, 12, 16, 20 or 24 MHz clock. */
+void delayMicroseconds(unsigned int us)
+{
+ // call = 4 cycles + 2 to 4 cycles to init us(2 for constant delay, 4 for variable)
+
+ // 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 >= 24000000L
+ // for the 24 MHz clock for the aventurous ones, trying to overclock
+
+ // zero delay fix
+ if (!us) return; // = 3 cycles, (4 when true)
+
+ // the following loop takes a 1/6 of a microsecond (4 cycles)
+ // per iteration, so execute it six times for each microsecond of
+ // delay requested.
+ us *= 6; // x6 us, = 7 cycles
+
+ // account for the time taken in the preceeding commands.
+ // we just burned 22 (24) cycles above, remove 5, (5*4=20)
+ // us is at least 6 so we can substract 5
+ us -= 5; //=2 cycles
+
+#elif F_CPU >= 20000000L
+ // for the 20 MHz clock on rare Arduino boards
+
+ // for a one-microsecond delay, simply return. the overhead
+ // of the function call takes 18 (20) cycles, which is 1us
+ __asm__ __volatile__ (
+ "nop" "\n\t"
+ "nop" "\n\t"
+ "nop" "\n\t"
+ "nop"); //just waiting 4 cycles
+ if (us <= 1) return; // = 3 cycles, (4 when true)
+
+ // the following loop takes a 1/5 of a microsecond (4 cycles)
+ // per iteration, so execute it five times for each microsecond of
+ // delay requested.
+ us = (us << 2) + us; // x5 us, = 7 cycles
+
+ // account for the time taken in the preceeding commands.
+ // we just burned 26 (28) cycles above, remove 7, (7*4=28)
+ // us is at least 10 so we can substract 7
+ us -= 7; // 2 cycles
+
+#elif 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 takes 14 (16) cycles, which is 1us
+ if (us <= 1) return; // = 3 cycles, (4 when true)
+
+ // the following loop takes 1/4 of a microsecond (4 cycles)
+ // per iteration, so execute it four times for each microsecond of
+ // delay requested.
+ us <<= 2; // x4 us, = 4 cycles
+
+ // account for the time taken in the preceeding commands.
+ // we just burned 19 (21) cycles above, remove 5, (5*4=20)
+ // us is at least 8 so we can substract 5
+ us -= 5; // = 2 cycles,
+
+#elif F_CPU >= 12000000L
+ // for the 12 MHz clock if somebody is working with USB
+
+ // for a 1 microsecond delay, simply return. the overhead
+ // of the function call takes 14 (16) cycles, which is 1.5us
+ if (us <= 1) return; // = 3 cycles, (4 when true)
+
+ // the following loop takes 1/3 of a microsecond (4 cycles)
+ // per iteration, so execute it three times for each microsecond of
+ // delay requested.
+ us = (us << 1) + us; // x3 us, = 5 cycles
+
+ // account for the time taken in the preceeding commands.
+ // we just burned 20 (22) cycles above, remove 5, (5*4=20)
+ // us is at least 6 so we can substract 5
+ us -= 5; //2 cycles
+
+#elif F_CPU >= 8000000L
+ // for the 8 MHz internal clock
+
+ // for a 1 and 2 microsecond delay, simply return. the overhead
+ // of the function call takes 14 (16) cycles, which is 2us
+ if (us <= 2) return; // = 3 cycles, (4 when true)
+
+ // the following loop takes 1/2 of a microsecond (4 cycles)
+ // per iteration, so execute it twice for each microsecond of
+ // delay requested.
+ us <<= 1; //x2 us, = 2 cycles
+
+ // account for the time taken in the preceeding commands.
+ // we just burned 17 (19) cycles above, remove 4, (4*4=16)
+ // us is at least 6 so we can substract 4
+ us -= 4; // = 2 cycles
+
+#else
+ // for the 1 MHz internal clock (default settings for common Atmega microcontrollers)
+
+ // the overhead of the function calls is 14 (16) cycles
+ if (us <= 16) return; //= 3 cycles, (4 when true)
+ if (us <= 25) return; //= 3 cycles, (4 when true), (must be at least 25 if we want to substract 22)
+
+ // compensate for the time taken by the preceeding and next commands (about 22 cycles)
+ us -= 22; // = 2 cycles
+ // the following loop takes 4 microseconds (4 cycles)
+ // per iteration, so execute it us/4 times
+ // us is at least 4, divided by 4 gives us 1 (no zero delay bug)
+ us >>= 2; // us div 4, = 4 cycles
+
+
+#endif
+
+ // busy wait
+ __asm__ __volatile__ (
+ "1: sbiw %0,1" "\n\t" // 2 cycles
+ "brne 1b" : "=w" (us) : "0" (us) // 2 cycles
+ );
+ // return = 4 cycles
+}
+
+void init()
+{
+ // this needs to be called before setup() or some functions won't
+ // work there
+ sei();
+
+ // 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(TCCR0A) && defined(WGM01)
+ sbi(TCCR0A, WGM01);
+ sbi(TCCR0A, WGM00);
+#endif
+
+ // set timer 0 prescale factor to 64
+#if defined(__AVR_ATmega128__)
+ // CPU specific: different values for the ATmega128
+ sbi(TCCR0, CS02);
+#elif defined(TCCR0) && defined(CS01) && defined(CS00)
+ // this combination is for the standard atmega8
+ sbi(TCCR0, CS01);
+ sbi(TCCR0, CS00);
+#elif defined(TCCR0B) && defined(CS01) && defined(CS00)
+ // this combination is for the standard 168/328/1280/2560
+ sbi(TCCR0B, CS01);
+ sbi(TCCR0B, CS00);
+#elif defined(TCCR0A) && defined(CS01) && defined(CS00)
+ // this combination is for the __AVR_ATmega645__ series
+ sbi(TCCR0A, CS01);
+ sbi(TCCR0A, CS00);
+#else
+ #error Timer 0 prescale factor 64 not set correctly
+#endif
+
+ // enable timer 0 overflow interrupt
+#if defined(TIMSK) && defined(TOIE0)
+ sbi(TIMSK, TOIE0);
+#elif defined(TIMSK0) && defined(TOIE0)
+ sbi(TIMSK0, TOIE0);
+#else
+ #error Timer 0 overflow interrupt not set correctly
+#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
+
+#if defined(TCCR1B) && defined(CS11) && defined(CS10)
+ TCCR1B = 0;
+
+ // set timer 1 prescale factor to 64
+ sbi(TCCR1B, CS11);
+#if F_CPU >= 8000000L
+ sbi(TCCR1B, CS10);
+#endif
+#elif defined(TCCR1) && defined(CS11) && defined(CS10)
+ sbi(TCCR1, CS11);
+#if F_CPU >= 8000000L
+ sbi(TCCR1, CS10);
+#endif
+#endif
+ // put timer 1 in 8-bit phase correct pwm mode
+#if defined(TCCR1A) && defined(WGM10)
+ sbi(TCCR1A, WGM10);
+#endif
+
+ // set timer 2 prescale factor to 64
+#if defined(TCCR2) && defined(CS22)
+ sbi(TCCR2, CS22);
+#elif defined(TCCR2B) && defined(CS22)
+ sbi(TCCR2B, CS22);
+//#else
+ // Timer 2 not finished (may not be present on this CPU)
+#endif
+
+ // configure timer 2 for phase correct pwm (8-bit)
+#if defined(TCCR2) && defined(WGM20)
+ sbi(TCCR2, WGM20);
+#elif defined(TCCR2A) && defined(WGM20)
+ sbi(TCCR2A, WGM20);
+//#else
+ // Timer 2 not finished (may not be present on this CPU)
+#endif
+
+#if defined(TCCR3B) && defined(CS31) && defined(WGM30)
+ sbi(TCCR3B, CS31); // set timer 3 prescale factor to 64
+ sbi(TCCR3B, CS30);
+ sbi(TCCR3A, WGM30); // put timer 3 in 8-bit phase correct pwm mode
+#endif
+
+#if defined(TCCR4A) && defined(TCCR4B) && defined(TCCR4D) /* beginning of timer4 block for 32U4 and similar */
+ sbi(TCCR4B, CS42); // set timer4 prescale factor to 64
+ sbi(TCCR4B, CS41);
+ sbi(TCCR4B, CS40);
+ sbi(TCCR4D, WGM40); // put timer 4 in phase- and frequency-correct PWM mode
+ sbi(TCCR4A, PWM4A); // enable PWM mode for comparator OCR4A
+ sbi(TCCR4C, PWM4D); // enable PWM mode for comparator OCR4D
+#else /* beginning of timer4 block for ATMEGA1280 and ATMEGA2560 */
+#if defined(TCCR4B) && defined(CS41) && defined(WGM40)
+ sbi(TCCR4B, CS41); // set timer 4 prescale factor to 64
+ sbi(TCCR4B, CS40);
+ sbi(TCCR4A, WGM40); // put timer 4 in 8-bit phase correct pwm mode
+#endif
+#endif /* end timer4 block for ATMEGA1280/2560 and similar */
+
+#if defined(TCCR5B) && defined(CS51) && defined(WGM50)
+ sbi(TCCR5B, CS51); // set timer 5 prescale factor to 64
+ sbi(TCCR5B, CS50);
+ sbi(TCCR5A, WGM50); // put timer 5 in 8-bit phase correct pwm mode
+#endif
+
+#if defined(ADCSRA)
+ // set a2d prescaler so we are inside the desired 50-200 KHz range.
+ #if F_CPU >= 16000000 // 16 MHz / 128 = 125 KHz
+ sbi(ADCSRA, ADPS2);
+ sbi(ADCSRA, ADPS1);
+ sbi(ADCSRA, ADPS0);
+ #elif F_CPU >= 8000000 // 8 MHz / 64 = 125 KHz
+ sbi(ADCSRA, ADPS2);
+ sbi(ADCSRA, ADPS1);
+ cbi(ADCSRA, ADPS0);
+ #elif F_CPU >= 4000000 // 4 MHz / 32 = 125 KHz
+ sbi(ADCSRA, ADPS2);
+ cbi(ADCSRA, ADPS1);
+ sbi(ADCSRA, ADPS0);
+ #elif F_CPU >= 2000000 // 2 MHz / 16 = 125 KHz
+ sbi(ADCSRA, ADPS2);
+ cbi(ADCSRA, ADPS1);
+ cbi(ADCSRA, ADPS0);
+ #elif F_CPU >= 1000000 // 1 MHz / 8 = 125 KHz
+ cbi(ADCSRA, ADPS2);
+ sbi(ADCSRA, ADPS1);
+ sbi(ADCSRA, ADPS0);
+ #else // 128 kHz / 2 = 64 KHz -> This is the closest you can get, the prescaler is 2
+ cbi(ADCSRA, ADPS2);
+ cbi(ADCSRA, ADPS1);
+ sbi(ADCSRA, ADPS0);
+ #endif
+ // enable a2d conversions
+ sbi(ADCSRA, ADEN);
+#endif
+
+ // 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(UCSRB)
+ UCSRB = 0;
+#elif defined(UCSR0B)
+ UCSR0B = 0;
+#endif
+}
projects / max / tmk_keyboard.git / blobdiff