Provide a FastLED specific version of wiring for the timing functions when on AVR to get more efficient TIMER0 interrupt handlers in place.

2 files changed, 306 insertions, 0 deletions

diff --git a/FastLED.h b/FastLED.h
index 07b26471..5c656aeb 100644
--- a/FastLED.h
+++ b/FastLED.h
@@ -308,6 +308,15 @@ static CLEDController &addLeds(struct CRGB *data, int nLedsOrOffset, int nLedsIf
 	CRGB *leds() { return (*this)[0].leds(); }
 };
 
+#ifdef FASTLED_AVR
+extern "C" {
+	unsigned long millis(void);
+unsigned long micros(void);
+void delay(unsigned long);
+void delayMicroseconds(unsigned int us);
+};
+#endif
+
 #define FastSPI_LED FastLED
 #define FastSPI_LED2 FastLED
 #ifndef LEDS
diff --git a/wiring.cpp b/wiring.cpp
new file mode 100644
index 00000000..f0e64087
--- /dev/null
+++ b/wiring.cpp
@@ -0,0 +1,297 @@
+#include "FastLED.h"
+
+#ifdef FASTLED_AVR
+extern "C" {
+// 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))
+
+typedef union { unsigned long _long; uint8_t raw[4]; } tBytesForLong;
+// tBytesForLong FastLED_timer0_overflow_count;
+volatile unsigned long FastLED_timer0_overflow_count=0;
+volatile unsigned long FastLED_timer0_millis = 0;
+
+LIB8STATIC void  __attribute__((always_inline)) fastinc32 (volatile uint32_t & _long) {
+  uint8_t b = ++((tBytesForLong&)_long).raw[0];
+  if(!b) {
+    b = ++((tBytesForLong&)_long).raw[1];
+    if(!b) {
+      b = ++((tBytesForLong&)_long).raw[2];
+      if(!b) {
+        ++((tBytesForLong&)_long).raw[3];
+      }
+    }
+  }
+}
+
+#if defined(__AVR_ATtiny24__) || defined(__AVR_ATtiny44__) || defined(__AVR_ATtiny84__)
+ISR(TIM0_OVF_vect)
+#else
+ISR(TIMER0_OVF_vect)
+#endif
+{
+  fastinc32(FastLED_timer0_overflow_count);
+  // FastLED_timer0_overflow_count++;
+}
+
+// there are 1024 microseconds per overflow counter tick.
+unsigned long millis()
+{
+        unsigned long m;
+        uint8_t oldSREG = SREG;
+
+        // disable interrupts while we read FastLED_timer0_millis or we might get an
+        // inconsistent value (e.g. in the middle of a write to FastLED_timer0_millis)
+        cli();
+        m = FastLED_timer0_overflow_count;  //._long;
+        SREG = oldSREG;
+
+        return (m*MICROSECONDS_PER_TIMER0_OVERFLOW)/1000;
+}
+
+unsigned long micros() {
+        unsigned long m;
+        uint8_t oldSREG = SREG, t;
+
+        cli();
+        m = FastLED_timer0_overflow_count; // ._long;
+#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)
+{
+        uint16_t start = (uint16_t)micros();
+
+        while (ms > 0) {
+                if (((uint16_t)micros() - start) >= 1000) {
+                        ms--;
+                        start += 1000;
+                }
+        }
+}
+
+/* Delay for the given number of microseconds.  Assumes a 8 or 16 MHz clock. */
+void delayMicroseconds(unsigned int us)
+{
+        // 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 >= 20000000L
+        // for the 20 MHz clock on rare Arduino boards
+
+        // for a one-microsecond delay, simply wait 2 cycle and return. The overhead
+        // of the function call yields a delay of exactly a one microsecond.
+        __asm__ __volatile__ (
+                "nop" "\n\t"
+                "nop"); //just waiting 2 cycle
+        if (--us == 0)
+                return;
+
+        // 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
+
+        // account for the time taken in the preceeding commands.
+        us -= 2;
+
+#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 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
+
+        // busy wait
+        __asm__ __volatile__ (
+                "1: sbiw %0,1" "\n\t" // 2 cycles
+                "brne 1b" : "=w" (us) : "0" (us) // 2 cycles
+        );
+}
+#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
+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);
+#elif defined(TCCR1)
+  #warning this needs to be finished
+#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
+  #warning 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
+  #warning 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 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);
+#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
+}
+};
+#endif