#ARDUINO PWM FREQUENCY SOFTWARE#

N = pre-scalar (set to 8 in my application)īased on the values of ICR1 from 1 to 65535 we get a frequency range from 15Hz to 1MHz. The output frequency is given by the formula: The number can be any value from 0 – 65535 (size = 16 bits). So in my application, I used Timer1, which is 16bit, and allows for a number to be stored in a register (ICR1), and the frequency is calculated based on that number. He uses Timer2 as an example, and while he explains everything in a great and easy to understand manner, the disadvantage there is that the user has to sacrifice one of the PWM outputs to gain the frequency adjustment on the other. While it is not the easiest read, it is much easier than reading the datasheet, and Ken has managed to bring it down to a few numbers. It is also available on the Arduino website, but over there it misses a few figures, so it is better to go to the original source. The second article which takes this to the next level is Ken Shirriff’s blog: Secrets of Arduino PWM. It also covers the issues you may encounter if you use that approach. This allows the user to use the different PWM signals at the prescaled frequencies without having to go through the ATmega328p datasheet. I found the following link very useful, and as it says, it is a very good cheat sheet: There is a lot of help on adjusting the frequencies. The Arduino offers six PWM outputs, and they are connected to three timers in the circuit in pairs:īeing connected to three different timers means that almost always these are not in sync, despite running off of one main clock, which is 16MHz in the case of the Arduino UNO. However, the challenge that faced me was producing a product that gave me a PWM signal(s) running on a variable frequency between 100Hz – 4kHz.

#ARDUINO PWM FREQUENCY SOFTWARE#

The product offers the user the ability to program in C language, and with a lot of libraries and open source software available, most applications are very easily achieved. Value − the duty cycle: between 0 (always off) and 255 (always on).The ARDUINO UNO is an amazing product that incorporates an ATmega328P onto a development board with a USB Bootloader. You do not need to call pinMode() to set the pin as an output before calling analogWrite(). Unlike the PWM pins, DAC0 and DAC1 are Digital to Analog converters, and act as true analog outputs. The Arduino Due supports analogWrite() on pins 2 through 13, and pins DAC0 and DAC1. Older Arduino boards with an ATmega8 only support analogWrite() on pins 9, 10, and 11.

On the Arduino Mega, it works on pins 2 - 13 and 44 - 46. On most Arduino boards (those with the ATmega168 or ATmega328), this function works on pins 3, 5, 6, 9, 10, and 11. Pins 3 and 11 on the Leonardo also run at 980 Hz. On the Uno and similar boards, pins 5 and 6 have a frequency of approximately 980 Hz. The frequency of the PWM signal on most pins is approximately 490 Hz. After a call of the analogWrite() function, the pin will generate a steady square wave of the specified duty cycle until the next call to analogWrite() or a call to digitalRead() or digitalWrite() on the same pin. It can be used to light a LED at varying brightness or drive a motor at various speeds. The analogWrite() function writes an analog value (PWM wave) to a pin. Using the period calculated above, duty cycle is calculated as − Period is the sum of both on and off times and is calculated as shown in the following equation −ĭuty cycle is calculated as the on-time of the period of time. Period − It is represented as the sum of on-time and off-time of PWM signal.ĭuty Cycle − It is represented as the percentage of time signal that remains on during the period of the PWM signal.Īs shown in the figure, T on denotes the on-time and T off denotes the off-time of signal. Off-Time − Duration of time signal is low. On-Time − Duration of time signal is high. There are various terms associated with PWM − A basic PWM signal is shown in the following figure. Pulse width modulation is basically, a square wave with a varying high and low time. PWM has many applications such as controlling servos and speed controllers, limiting the effective power of motors and LEDs. Pulse Width Modulation or PWM is a common technique used to vary the width of the pulses in a pulse-train.

Arduino pwm frequency