Skip to main content

Current draw of ATtiny85 ticking clock using watchdog timer

I modified the previous watchdog timer code to test the current draw of ATtiny85 ticking a clock using POWER_DOWN deep sleep.

 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
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
#include <avr/io.h>
#include <avr/wdt.h>
#include <avr/sleep.h>
#include <avr/interrupt.h>
#include <avr/power.h>

#define TIMER0_PRESCALER 1024
#define OCR0A_DEFVAL ((byte)(F_CPU / (float)TIMER0_PRESCALER * 200/1000.0) - 1)
#define adc_disable() (ADCSRA &= ~(1<<ADEN)) // disable ADC (before power-off)

volatile byte timer0_tickpin = PB3;
volatile bool wdtimer = false;

void startTimer0() {
  // Set prescaler to 1024, thereby starting Timer0
  TCCR0B = bit(CS02) | bit(CS00); 
}

void stopTimer0() {
  // Set prescaler to 0, thereby stopping Timer0
  TCCR0B = 0;
}

// Interrupt service routine for Timer0
// The effective outcome is to toggle tickpin high for 100ms, then rest for 200ms
ISR(TIMER0_COMPA_vect) {
    stopTimer0();
    digitalWrite(timer0_tickpin, LOW);
    timer0_tickpin = (timer0_tickpin == PB3 ? PB4: PB3);
}

ISR(WDT_vect) {
  wdtimer = true;
}

void setup() {
  pinMode(PB3, OUTPUT); digitalWrite(PB3, LOW);
  pinMode(PB4, OUTPUT); digitalWrite(PB4, LOW);

  power_adc_disable();

  // Reset prescalers for Timer0 and Timer1
  GTCCR |= bit(PSR0) | bit(PSR1);

  // Setup Timer0 (but don't run it yet)
  TCCR0A = 0;
  TCCR0B = 0;
  TCNT0  = 0;
  TCCR0A = bit(WGM01); // CTC mode
  OCR0A = OCR0A_DEFVAL;

  // Interrupt on compare match with OCR0A
  TIMSK |= bit(OCIE0A);

  // Set up watchdog timer
  MCUSR &= ~_BV(WDRF);
  WDTCR |= (_BV(WDCE) | _BV(WDE));   // Enable the WD Change Bit
  WDTCR =   _BV(WDIE) |              // Enable WDT Interrupt
    _BV(WDP2) | _BV(WDP1);           // Set Timeout to ~1 seconds (or something)

  set_sleep_mode(SLEEP_MODE_PWR_DOWN);
  sleep_mode();
}

void loop() {
  if (wdtimer) {
    wdtimer = false;
    digitalWrite(timer0_tickpin, HIGH);
    startTimer0();
    set_sleep_mode(SLEEP_MODE_IDLE);
    sleep_mode();
  } else {
    set_sleep_mode(SLEEP_MODE_PWR_DOWN);
    sleep_mode();
  }
}

In summary, the watchdog timer wakes up the ATtiny85 every sec. The tickpin is toggled within a 200ms window using IDLE sleep (via Timer0), then it will go back to deep sleep for 800ms. The current draw as measured is 1.7mA.

If the deep sleep current draw of the D1 Mini can be reduced from 0.8 to 0.1mA by using a barebones ESP8266, then the current draw of the ATtiny85 is only 1mA.

Comments

Popular posts from this blog

Update: Line adapter for Ozito Blade Trimmer

Update (Dec 2021): If you access to a 3D printer, I would now recommend this solution , which makes it super easy to replace the trimmer line. I have been using it for a few months now with zero issue.

Attiny85 timer programming using Timer1

This Arduino sketch uses Timer1 to drive the LED blinker: 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

Line adapter for Ozito Blade Trimmer

This is an adapter for Ozito 18V battery trimmer (and possibly some Bosch trimmers as well) that uses a plastic blade for cutting. It lets you insert a 2.4mm trimmer line (about 8cm long) and use that for cutting. Simply cut a length of trimmer line and briefly heat up one end with a lighter so that a little bulb is formed. Then insert the trimmer line into the adapter and slot that into the trimmer as per normal. Make sure the trimmer line is not so long that it touches the safety guard. If that is the case, simply trim off any excess with a cutter or scissors. This part is best printed using PETG, which is a tougher and more flexible material. PLA is more rigid and breaks more easily. However, even with PETG, it will still break when it hits something really hard. Since this takes only 0.5m of material and 15 minutes to print, I will usually print a batch of nine at a time at very little cost. The blades that they sell do not break when it hits a hard object, but