Almost all boards work similarly with few exceptions. The Arduino boards are widely used in the automation industry and embedded projects. The Arduino Mega 2560 Rev3 is a microcontroller board that is based on the ATmega2560 microcontroller. In this post today, I’ll walk you through the Introduction to Arduino Mega 2560 Rev3. but in case you want the 25khz, the manual for the avr chip has been included with the pages to look at.Hi Friends! Hope you’re well today. I would recommend in this case to use the defaults that marlin has set. for example output pin cross talk may or may not be an issue as well. This should show specific names of what timers are used, and what pre-scaler options can be set.Ĭhanging timer values can have unintended consequences, such as noise on analog to digital pins, and overall voltage stability of chip in general. so look after page 47 in the manual for the 8 bit at-mega 2560. You will need to change the pre-scaler value of the timer in question. more info here on timers Īnd specifics on atmega 2560 here it might do that or in your case it might all work ok. as the answer might break the rest of the avr or at least cause issues of troubleshooting reboots, bad adc measurements and so on. It is hard to answer question with a good answer. I was able to find this bit of code in "temperature.h" which I think means it depends on which pins are defined for fans but I'm not sure how it'll handle multiple fans if that's the case (which timer will be chosen? each timer for its respective pins? )Įdited 3 time(s). Static void set_pwm_frequency(const pin_t pin, int f_desired) Static Timer get_pwm_timer(const pin_t pin) Volatile uint16_t* ICRn // max 1 ICR register per timer Volatile uint16_t* OCRnQ // max 3 OCR registers per timer Volatile uint8_t* TCCRnQ // max 3 TCCR registers per timer Static void setPwmFrequency(const pin_t pin, int val) (see Configuration_adv.h -> FAST FAN PWM Settings) * NOTE that there are limitations, particularly if using TIMER2. * NOTE that the frequency is applied to all pins on the timer (Ex OC3A, OC3B and OC3 * resolution values required and sets the timer registers accordingly. * calculates the required waveform generation mode, prescaler and * as close as possible to the provided desired frequency. * Sets the frequency of the timer corresponding to the provided pin * Used by set_pwm_frequency, set_pwm_duty * returns Timer struct containing this information * Grabs timer information and registers of the provided pin #define FAST_PWM_FAN_FREQUENCY 31400 // Define here to override the defaults below Removes the PWM noise but increases heating in the FET/Arduino #define FAST_PWM_FAN // Increase the fan PWM frequency. * USE_OCR2A_AS_TOP sacrifices duty cycle control resolution to achieve this broader range of frequencies. Only use this option if you don't need PWM on 0C2A. But note that this option blocks the use of * A greater range can be achieved by enabling USE_OCR2A_AS_TOP. * Boards that use TIMER2 for PWM have limitations resulting in only a few possible frequencies on TIMER2: * Setting very high frequencies can damage your hardware. * NOTE: Setting very low frequencies (< 10 Hz) may result in unexpected timer behavior. * and not to complete it when users are not aware that the frequency must be specifically set to support the target board. * This F value is only to protect the hardware from an absence of configuration * For non AVR, if left undefined this defaults to F = 1Khz. * i.e., F = 31.4kHz on 16MHz microcontrollers or F = 39.2kHz on 20MHz microcontrollers. * For AVR, if left undefined this defaults to F = F_CPU/(2*255*1) * to produce a frequency as close as possible to the desired frequency. * Combinations of PWM Modes, prescale values and TOP resolutions are used internally With the same price as 3.2, I'll have unused pins for 2 more fans?Įdited 4 time(s). using another MCU (Attiny85 or ATmega328) to read the 1 kHz PWM and generate 25 kHz accordingly (4$) : I don't know if PLL preserves the duty cycle or notĤ. using PLL frequency multiplier from 1 to 25 kHz :ģ.1. I'll have to send Marlin's fan control commands through I2cģ. using a standalone driver with 25 kHz output like MAX31790 (which I can't source, any alternatives?) : I don't know If there are any unused timers by Marlin or not, and if there are, is it possible without affecting its other functionalities?Ģ. I don't think I need to worry about phase and only need to control the duty cycle and frequency(?)Īfter searching I came up with a couple of options but I don't know which is easier or more plausible so here I am
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