Laser power control via PPI instead of PWM

[o_lampe]

Hi Dev-team,
I've played a few days with the K40 laser and the meerk40t firmware (which only runs with the original M2 controller).
What I like most is the power control over pulse per inch algorhythm. It produces always the same grayscale, no matter how fast the axis moves. From the looks, it also works at the turning points where we usually see (with PWM control) darker engraving due to deceleration/acceleration.
For image raster engraving we only have to define max. power for black, the lighter colours follow a bezier curve to adapt for non linear laser behaviour.
The power supply of the K40 supports up to 1000ppi, which allows us to fire the laser a few times per pixel.
It would be cool to implement this in RRF laser mode, too!

//edit found a Video, which explains it much better.
//edit 2 Sorry, this Video I had in mind

[gloomyandy]

@o_lampe Have you tried a recent beta of RRF? That should include some improvements in the way that the laser power is adjusted over a move that may get close to what you are looking for. RRF for some time now has adjusted the laser power over the length of a move to take into account the speed and acceleration, but there have been some recent changes that should have improved that algorithm. My understanding is that it just uses a simple linear adjustment such that the power will be zero at the turn around point (when the velocity is zero). However it may be that the frequency of this adjustment (I seem to remember that it uses a timer based mechanism to adjust the pwm values), may not I think you have seen the results obtained in this thread: https://forum.duet3d.com/topic/19555/ghosting-laser-while-rastering?_=1641308239707

[o_lampe]

@gloomyandy
Yes I've read that thread. It retriggered my interest in laser-stuff, which was gone due to diode laser issues.
If I understood the second video correctly, their ppi is directly connected to the (X-)stepper pulses. E.g. at 500ppi every other stepper pulse also fires the laser. That's equally simple and elegant, IMHO.
No need for extra timer routines etc.