Laser M3 S argument

chege54 · July 9, 2021, 9:09pm

Hi Guys
I would have a small question regarding the snapmaker M3 command. As I have seen in the snapmaker custom M3_M4 gcode parser, they are using “P” argument to define the spindle speed or laser power. But I have checked the generated luban gcode and there the actual command is looking like this: “M3 P35 S89” in case of 35% laser power. What is the use case of the S part? Is just a legacy or compatibility stuff? Thanks

brent113 · July 10, 2021, 6:31am

It’s redundant and unneeded, and ignored by the firmware.

github.com

Snapmaker/Snapmaker2-Controller/blob/74b0f11138c698a136b3ac79983b219952a81d8b/snapmaker/src/gcode/M3-M5.cpp#L75

    
      
          
          
planner.synchronize();   // wait until previous movement commands (G0/G0/G2/G3) have completed before playing with the spindle
          
          
/**
           * Our final value for ocr_val is an unsigned 8 bit value between 0 and 255 which usually means uint8_t.
           * Went to uint16_t because some of the uint8_t calculations would sometimes give 1000 0000 rather than 1111 1111.
           * Then needed to AND the uint16_t result with 0x00FF to make sure we only wrote the byte of interest.
           */
           
          if(laser.IsOnline()) {
            if(parser.seen('P')) {
              laser.SetOutput(parser.value_float());
            }
            else {
              laser.TurnOn();
            }
          }
          else if(cnc.IsOnline()) {
            if(parser.seen('P'))
              cnc.SetOutput(parser.value_float());
            else

chege54 · July 10, 2021, 7:16am

thanks for the feedback. That was my assumption also.
Beside of this, based on the code I have seen snapmaker uses a lookup table for the PWM, and the table starts from 20. So 1% power == PWM 20. But If you generate the gcode: “M3 P1 S2”
So “S” will be 2, not 20 that was a bit contradicting to me

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Laser M3 S argument

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