If you change timer0 registers, this may influence the Arduino timer function. In the Arduino world timer0 is been used for the timer functions, like delay(), millis() and micros(). In the Arduino firmware all timers were configured to a 1kHz frequency and interrupts are gerally enabled. The timer hardware can be configured with some special timer registers. So be careful when writing your own timer functions. Normally the system clock is 16MHz, but for the Arduino Pro 3,3V it is 8Mhz. The timer3, timer4 and timer5 are all 16bit timers, similar to timer1.Īll timers depends on the system clock of your Arduino system. Timer 0, timer1 and timer2 are identical to the ATmega168/328. Also identical only differs in memory size. The controller for the Arduino Mega series is the Atmel AVR ATmega1280 or the ATmega2560. 8bits means 256 values where 16bit means 65536 values for higher resolution. The most important difference between 8bit and 16bit timer is the timer resolution. Timer0 and timer2 are 8bit timer, where timer1 is a 16bit timer. Both have 3 timers, called timer0, timer1 and timer2. These chips are pin compatible and only differ in the size of internal memory. The controller of the Arduino is the Atmel AVR ATmega168 or the ATmega328. You can configure the prescaler for the timer, or the mode of operation and many other things. The timer can be programmed by some special registers. It is like a clock, and can be used to measure time events. Even the Servo library uses timers and interrupts.Ī timer or to be more precise a timer / counter is a piece of hardware builtin the Arduino controller (other controllers have timer hardware, too). The PWM functions analogWrite() uses timers, as the tone() and the noTone() function does. Many Arduino functions uses timers, for example the time functions: delay(), millis() and micros() and delayMicroseconds(). As Arduino programmer you will have used timers and interrupts without knowledge, bcause all the low level hardware stuff is hidden by the Arduino API. This tutorial shows the use of timers and interrupts for Arduino boards. Added ArduinoTimer101.zip examples source code for Arduino v1.x .Example 3 has been updated to work with Arduino v1.x.Please note, not all PWM mode are available on all clocks. Setting this to 400 results in a PWM frequency on the Arduino Mega pin of 16Mhz / 400 = 47304Hz, or possibly half that! The duty cycle is then changed by setting OCR4A or B to some value between 0 and 400įurther reading of the datasheet will explain all the registers, but hopefully this will point you in the right direction The actual frequency of the PWM is a function of these settings and the final entry, the input capture register. We have selected no prescaling, which corresponds to the native 16Mhz frequency of the Arduino clock. The CS bits relate to the clock selection, see table 17-6 in the datasheet. We have set it to mode 14, which is fast PWM with ICRn used as the maximum for the counter. The 4 statements relating to the WGM bits control the mode of operation of the PWM. Please note that the control registers 4, sections A & B will effect the PWM on all the OCR4n pins, see table above. Please see section 17.9 in the datasheet. These control the type, range and frequency of the PWM generated by the Arduino. We need to look at the timer counter control registers. This is extremely annoying as it produces a nasty noise when operating DC or stepper motors by PWM. One of the most annoying aspects of the native arduino PWM commands is that the PWM frequency is set to a value which is audible. How to change the frequency and range of the Arduino PWM? Now we can change the duty cycle using just the register Using the register is slightly faster.įirst we set the pin to output and use the analogWrite command to initialise the PWM Very simply we can use the register to set the duty cycle instead of the analogWrite command. How can we use this information on PWM registers? The following table gives the Arduino pin number and the corresponding register for controlling the duty cycle Arduino Pin Which Arduino Mega pins map to which registers in the ATMEL microcontroller? Normally you do this with the analogWrite() command, however, you can access the Atmel registers directly for finer control over the PWM on an Arduino including changing the type, range and frequency of the pulse width modulation PWM. The Arduino Mega 2560 has 15 pins which can be used for PWM output.
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