Timer0 on the Attiny84 has an 8-bit and Timer1 a 10-bit counter. CS12Įvery timer has a counter, which is incremented on every tick of the timer. The prescaler is set with the bits CS12, CS11 and CS10. With a prescaler of 256 the timer ticks once for every 256 CPU clock ticks. The prescaler divides the CPU clock frequency into smaller chunks.
ARDUINO ANALOGWRITE VS CLOCK OUTPUT PWM FULL
With no prescaler enabled, the timer ticks at the full speed of the CPU clock frequency, which is usually too high for any practical purposes. This looks very complicated, but it is actually quite easy if you read the datasheet. The following table shows all the bits for the registers TCCR1A and TCCR1B. By setting and unsetting the bits in these registers, we can control the behavior of the timer. These registers are called "Timer/Counter Control Register" or TCCR for short. Register DescriptionĮvery timer has two registers to set its mode of operation. Timer0 works essentially the same, with some minor differences, which are outlined in the datasheet. For the sake of brevity I will describe only the configuration of Timer1 in this post. So by changing the frequency of Timer0 a lot of libraries will stop working correctly.
Timer0 is used by the Arduino environment for timing functions like delay(), millis() and micros() and many libraries depend on these. The pins 5 and 6 (Arduino digital pins 8 and 7 respectively) are controlled by Timer0 and the pins 7 and 8 (Arduino digital pins 6 and 5 respectively) are controlled by Timer1. The Attiny84 has two timers called Timer0 and Timer1 and four PWM pins. All this information can be obtained by reading the datasheet for the particular chip. Every PWM-pin is controlled by a certain timer and different chips have different timers. On the Attiny84 and other Atmel chips only certain pins can be used for PWM output.
ARDUINO ANALOGWRITE VS CLOCK OUTPUT PWM HOW TO
This post shows how to set these flags and how to create really high frequencies like 4 MHz. To change the frequency, you have to set the appropriate flags in the Attinys registers manually. The default frequency seems to be either 250 Hz or 500 Hz, which is clearly not enough for certain use cases. The problem is, that you cannot set the frequency of the output square wave. The variable dut圜ycle can be set to a value between 0 and 255, whereby 0 means the pin is always off and 255 means it's always on. The Arduino API allows you to use PWM and set the duty cycle with the function analogWrite(), which also works on the Attiny84: byte PWM_PIN = 6 This relation is given as a percentage and is called the duty cycle. The power supplied to the device is determined by the length of time the pin is on versus off. It works by switching a digital pin on and off at a high frequency. Pulse-width modulation can be used by a microcontroller to control the power supplied to other devices like LEDs or motors. How to set the PWM-frequency for the Attiny84 Author Andreas Rohner Date Tue Category Electronics How to set the PWM-frequency for the Attiny84 My Notebook
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