The pins on the Pico board were already tested and they show the presence of 12V. I must test the laser itself because I’m starting having doubts of it’s functionality… Didn’t know you can add the same +12V to the PWM pin. It’s really a safe thing to do? The laser was pretty expensive and I do not want to blew it! 
Really thank you for your patience!
Well I did the test anyway but there is no laser action… 
Reading this thread reminds me of the old laser warning:
Don’t look into the laser with your remaining eye
Well, I can look with both of them, cause it’s not working!!
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Hi again,
I have another guess … maybe it is something with the GPIO pins. Pico has two gpio20, one for FAN3 port and same gpio20 for laser port. I guess I am controlling the one for the FAN3 port because like I said the small LED is acting accordingly on the M3 and M5 commands. The question is how do I “transfer” this to the laser port?
Found some information’s here and here but still not enough … I’m pretty sure that even if there are 2 gpio20 only one is generating the PWM signal and in this case obviously is the FAN port… Somehow I must route that to the laser port.
You can put +12V on PWM laser pin ONLY if laser specification said you can go 12V on PWM, or you can break the control board (not sure if its affects laser diod too).
Did you check gpio20 on laser pin PWM + GND pin using multimeter ? It must be about 3.3V if you go laser power 100% with SET_PIN command.
You can go for FAN pin as PWM source, but its will be inverted, i have schema to make it right, but not tested et
Also make sure laser PWM minimal V is 3
Thanks again! I have tested the pins with multimeter but honestly I forgot the value… will test again soon when I’m back home.
So there is precisely 3.3V between the PWM pin and the GND.
And your laser is working (with +12V in PWM)
And mother board have +3.3V
But laser not working from motherboard…
I don’t see you said if laser support +3V for PWM, a-a-and take multimeter to check laser cable output, also while connected (if possible, you can use needles to gently penetrate cable if you don’t have options to use multimeter while cable is connected, just care if you have separation of 12v / gnd / pwm wires in this cable). As said, protect your eyes.
With the laser came a small piece of paper with the following:
- Operating voltage 12V
- PWM / TTL input 3.3-12V
- Prefered 5 KHz
With the laser module connected and all electronics started, I’ve commanded the laser from Mainsail to Fully ON and measured the voltage on the pins. The voltages are correct 12V between GND and (+) pin and 3.3V between PWM and GND. This 3.3 oscilates correctly as I modify the power from Mainsail.
So everything is ok but the laser module does not fire…
Do you have a datasheet for the laser? A “small piece of paper” is generally not considered a reliable source.
I would suggest powering the laser with 12V and connect the “PWM/TTL input” to 12V as well and see if the laser fires.
My suspicion is that the even though the small piece of paper says the laser works with a 3.3V control, it actually doesn’t.
Check pwm votage on laser while connected
You can try to get +12V PWM from fan pin, but IT WILL BE INVERTED, means 0 = 1, care your eyes
I have already done that… (described couple of posts above) and laser not working.
I guess I know what is the problem… The SKR board generates PWM signal between 0-3.3V and the laser requires between 3.3-12V. I have tried to connect the FAN (+) pin to the PWM pin on laser module but the board does not start / boot. I can try to start everything and after that connect the FAN( +) to laser PWM…
Fan(+) must be just connection to +12v.
Controlled pin is another.
Check with multimeter and on laser end too.
But this way I will not control the PWM oscillation for the laser, this way I will oscilate the power of the module itself… or am I missing something?
There +12v goes to motherboard from outside. And its goes to fan+ pin.
If you open PDF on github with pins, you will see another fan pin marked by gpio number - this pin is where PWM can go out. But it will be in inverted state, because if you turn on the fan it need +12v and GND. +12v pin is here always +12v (actually it is what VCC is, the + from power supply), and GND appears when mcu send “high” (+3.3v) signal.
Hello,
Well, in very simple words… I found the problem! But what a journey… hours and hours, days of work in vain! Unbelievable! I’m so tired and empty that I can not express myself… Last night I decided to abandon the fight and opened up the laser module, maybe is something wrong over there, I thought. Only 4 screws that holds the small module on the heatsink that hides the laser diode. Well, guess what? One of the 2 leads that goes to the laser diode was unsoldered, disconnected, in air… I mean, how on Earth can happen such thing? The diode is in it’s brass heatsink and that is the big aluminum heatsink (down the hole), impossible to reach, impossible to take out, impossible to re-solder… I could try to heat up the aluminum maybe it will release the brass tube, but… I’m just tired