This Arduino sketch uses Timer1 to drive the LED blinker:
The internal RC oscillator can have a factory variance of up to 10%. I observe that my blinker pulsed slightly faster than 1Hz.
Thankfully, unlike the watchdog oscillator, the internal RC oscillator can be calibrated by using the OSCCAL register, or adjusting the value of OCR1A. I believe it should not be too difficult to automatically calibrate the oscillator between NTP calls by taking the difference in actual time and clock time (in seconds) and adjust OCR1A accordingly to get as close to 1Hz as possible.
So on initial startup, the ESPCLOCK may not be pulsing at 1Hz, but after 15 or 30 minutes, it should be fully calibrated.
The downside with this approach is we can only use SLEEP_MODE_IDLE to keep Timer1 running during sleep, which is not as power efficient as using the Watchdog Timer.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 | /* * Program ATTiny85 to blink LED connected to PB1 at 1s interval. * Assumes ATTiny85 is running at 1MHz internal clock speed. */ #include <avr/io.h> #include <avr/wdt.h> #include <avr/sleep.h> #include <avr/interrupt.h> bool timer1 = false, led = true; // Interrupt service routine for timer1 ISR(TIMER1_COMPA_vect) { timer1 = true; } void setup() { // Setup output pins pinMode(1, OUTPUT); digitalWrite(1, led); set_sleep_mode(SLEEP_MODE_IDLE); // Setup timer1 to interrupt every second TCCR1 = 0; // Stop timer TCNT1 = 0; // Zero timer GTCCR = _BV(PSR1); // Reset prescaler OCR1A = 243; // T = prescaler / 1MHz = 0.004096s; OCR1A = (1s/T) - 1 = 243 OCR1C = 243; // Set to same value to reset timer1 to 0 after a compare match TIMSK = _BV(OCIE1A); // Interrupt on compare match with OCR1A // Start timer in CTC mode; prescaler = 4096; TCCR1 = _BV(CTC1) | _BV(CS13) | _BV(CS12) | _BV(CS10); sei(); } void loop() { if (timer1) { timer1 = false; led = !led; digitalWrite(1, led); } sleep_enable(); sleep_cpu(); // CPU goes to sleep here; will be woken up by timer1 interrupt } |
The internal RC oscillator can have a factory variance of up to 10%. I observe that my blinker pulsed slightly faster than 1Hz.
Thankfully, unlike the watchdog oscillator, the internal RC oscillator can be calibrated by using the OSCCAL register, or adjusting the value of OCR1A. I believe it should not be too difficult to automatically calibrate the oscillator between NTP calls by taking the difference in actual time and clock time (in seconds) and adjust OCR1A accordingly to get as close to 1Hz as possible.
So on initial startup, the ESPCLOCK may not be pulsing at 1Hz, but after 15 or 30 minutes, it should be fully calibrated.
The downside with this approach is we can only use SLEEP_MODE_IDLE to keep Timer1 running during sleep, which is not as power efficient as using the Watchdog Timer.
Hi .help me to change the function from arduino codes at attyni85 usb .please help with .thanks
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// put your setup code here, to run once:
//timer2
OCR2A = 127; //50% duty cycle
TCCR2A = _BV(COM2A0) | _BV(WGM21) | _BV(WGM20); //toggle output, fast PWM mode
TCCR2B = _BV(WGM22) | _BV(CS21) | _BV(CS20); // fast PWM mode, prescale 1:64
pinMode(11, OUTPUT);
}
void loop()
{
delay(200); //duration of each frequency
OCR2A += 10; //step size of frequency change
if(OCR2A >= 245){OCR2A = 10; } //range of sweep, 245 is max.
}
there are only 2 timers on attiny85, timer0 and timer1
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