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gnea / grbl

An open source, embedded, high performance g-code-parser and CNC milling controller written in optimized C that will run on a straight Arduino
https://github.com/gnea/grbl/wiki
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QUESTION: Modifying Laser/Spindle Frequency to ~20-kHz #738

Open cnburke opened 5 years ago

cnburke commented 5 years ago

I hate to open another issue for a question, but here goes:

Looking at trying to modify the PWM output of the variable spindle PWM to get close to 20kHz. The pre-scalars don't quite offer up what I'm hoping to achieve. I'm trying to understand the results of meddling with the PWM timer registers, but I'm also worried I'm going to affect something negatively, as all of the timer resources are tightly managed.

Is there any direction that could be given towards being able to modify the PWM frequency to a more custom frequency?

beckmx commented 4 years ago

I would put another atmega (tiny at least) in the port to avoid messing with the main code, that would allow you to update its firmware in a controlled way

bdurbrow commented 4 years ago

Can you switch to an Arduino Mega (and the Mega version of Grbl)? The timers on the ATMega2560 are more flexible...

rafaelalvesferreira commented 4 years ago

@cnburke, I'm on the same page. I'm looking for a laser module that the PWM operates in 3.3V (problem solved with a Bi-Directional Logic Level Converter) and a frequency between 20-50kHz.

Without the prescaler we can get 62.5kHz on the fast PWM mode. Looking better at the Avr datasheet I found that using the phase correct PWM mode we get half of it (31.25kHz) because the counter goes from 0 to 255 and back to 0. This way I'd be within the working range.

What I wonder, and it's my doubt, changing from fast PWM to phase correct PWM have any effect on the overall code? The fast PWM was choosen by any specific reason?

Tks

jak-pan commented 4 years ago

I'm also looking for 31.25kHz because my controller needs 20+kHz to operate.