Which FIRMWARE ??? grbl / smoothieware/ marlin / G2core / ???

[Frogblender]

I have a new 40W laser cutter build, which uses an Arduino DUE and ramps1.4 breakoutboard.

I have bludgeoned Marlin to work, but it has a couple of deal-breakers:

- Marlin does not ramp the laser power when accelerating/decelerating (ie. corners. This means corners get burned).
- Marlin PWM does not work at 25kHz (which is pwm frequency required for K40 power supplies), so laser power is either 100% ON or 100% OFF.

My must-haves:
- must run on DUE (perhaps not mandatory - I like due cuz it is super cheap and super powerful and pin-compatible with five-dollar ramps boards).
- must ramp laser power during accel/decel, to avoid scorched corners


Any advice would be greatly appreciated.

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[109jb]

First I'll say I'm not a laser guy but am a Grbl user on milling machine and am active on the Grbl github site. I have been thinking about trying laser out on my mill. anyway, here is what I know:

Grbl in general is stable and rock solid and has 2 current repositories that are kept up to date. One is for the Uno (328p) type platforms and the other is for the Mega 2560 platform. These 2 repositories are kept up to date.

There is a large laser user base and many of the things implemented are laser specific. I occasionally see posts about laser topics and most are configuration questions, not problems with how laser mode works. As I understand it, the laser mode has many features and can be read about here: https://github.com/gnea/grbl/wiki/Grbl-v1.1-Laser-Mode

As for using on the DUE, I'm sure there are ports, but who knows how up to date they are, or if maintained at all. The main programmer for Grbl is working on an ARM port with a HAL so that porting to any ARM platform should be much easier. For now the "official" versions are 328p and mega 2560. That said, the Mega2560 may work for you and only costs a few dollars. It is compatible with the RAMPS boards already.

Here is the Mega2560 verion on github https://github.com/gnea/grbl-Mega/wiki

[jfong]

I use both smoothieware and grbl-lpc on a cohesion3d board. This board uses the same 32bit mcu as the smoothieboard. With Lightburn laser software, it controls my k40 laser. Since it is a fast ARM board, it has no problem running quick raster image scanning. Both firmware supports variable laser power and will lower power when the laser slows down. Grbl-lpc runs gcode raster faster than smoothie.

I also have a DUE but do to the available firmware limitations, its not a good board to be using for a laser. I would use a 8bit Uno running grbl before using a DUE.

There is also a grbl port for the stm32 that is starting to get popular for lasers. Look up gerbil laser for the new controller board.

[Frogblender]

Much thanks to the above two dudes. I ended up taking their advice, dropped in my 8bit mega2560, installed grbl, and 5 hours later, my laser is running.

So to partially summarize: as of June2019:

- don't use Marlin for a laser (it lacks 25kHz laser PWM control, and does not modulate laser power vs. velocity).
- grbl on a mega2560 is OK. Works, but rastering is slow.

[jfong]

The arduino UNO or Mega2560 both run at 16mhz so same raster speed. Although you could change the xtal to 20mhz and recompile for the higher speed. They work fine for vector cutting but as you noticed, rasters can be slow. The 32bit controllers (lpc1769 for smoothie/grbl and STM32 for grbl) will run raster 3-4x faster. Depends on DPI density of the image.

https://embeddedtronicsblog.wordpress.com/

If you want to move up to a 32bit board.
This is my various 32bit firmware versions of grbl, smoothie, stm32, ESP32 that I have tested and can be used on a laser.

[Frogblender]

The arduino UNO or Mega2560 both run at 16mhz so same raster speed. Although you could change the xtal to 20mhz and recompile for the higher speed. They work fine for vector cutting but as you noticed, rasters can be slow. The 32bit controllers (lpc1769 for smoothie/grbl and STM32 for grbl) will run raster 3-4x faster. Depends on DPI density of the image.

https://embeddedtronicsblog.wordpress.com/

If you want to move up to a 32bit board.
This is my various 32bit firmware ports of grbl, smoothie, stm32, ESP32 that can be used on a laser.

So... you've tried just about every permutation of cpu (lpc17xx / STM32 / esp32 / mega / DUE) and firmware (grbl / smoothie).

Huh.

I'm particularly intrigued by your ESP32 grbl port (that is yours, correct?), seeing as esp32 is cheap, has wifi, and out-muscles (two freaking cores? 240MHz? dang.) all the above micros (except maybe stm32 m7?) - is esp32-grbl the future? Did you have problems with espressif's mushy rtos causing stepper pulse jitter?

I want.

[jfong]

Not my port, by Bart Dring, I’m just testing functionality. Under high speed rasters, there is jitter. I opened up a github issue #78 with Bart and he knows about the problem. I sent him scope and logic capture data of the jitter. It’s a problem that I suspect can’t be fixed. Under normal vector cutting speeds, it is fine.

I meant that there are pre compiled versions of most of the firmware that I have tested available for download.

grbl-lpc is the only firmware I have added code too. It’s not being actively maintained and I added code for the Cohesion3d laserboard trinamic drivers digital pot selection and a few minor bug fixes. I was the hardware beta tester for that board. I put it through months of testing before the designer release it for sale.

The STM32 grbl version is rather nice since the dev board can be bought for $2 on eBay. It can do rasters pretty fast too.

[jfong]

Here’s is another STM32 firmware, mini gerbil, that I tested.

https://embeddedtronicsblog.wordpres...rbil-firmware/