M92 and M350 and External Drivers



  • Hi,

    I have some questions about the correct use of M92 and M350 for external drivers.

    From the documentation:

    When M350 is processed, the steps/mm will be adjusted automatically to allow for any changes in microstepping. Therefore you can either:

    a) Set Steps/mm correctly for the default 1/16 microstepping, then set the microstepping to the desired amount using M350:

    1st question: Since only whole steps can be sent to external drivers does M350 even apply.

    2nd question: Why did what happened as described below happen?

    Thinking I should use both M92 and M350 my first settings in config.g where these:

    M92  X3276  Y3276
    M350 X1  Y1   I0
    

    After booting M92 reported X204.75 Y204.75 which is correct for the hardware and also is 3276 / 16.

    So it seemed to make sense. The values of 3276 for 16x where divided by 16 for 1x.

    The external drivers were working just fine and the movement amount was absolutely correct.

    But this is where things went wonky.

    I like on occasion to execute M98 P"config.g" from the console to see if any issues are reported.

    So I did and and all was good except M92 now reported X3276 Y3276. The M92 values were no longer being adjusted based on the M350 values. And, as you would expect, the axes movements were decidedly incorrect - rather exciting in fact.

    So what happened?


    For now I am using M92 X204 Y204 with no M350 command and all seems good and survives M98 P"config.g".

    Thanks.

    Frederick



  • @fcwilt said in M92 and M350 and External Drivers:

    The M92 values were no longer being adjusted based on the M350 values

    You can put it that way: The M92 values were still adjusted to the M350 values, but_no_longer to the default value of M350.


  • administrators

    @fcwilt said in M92 and M350 and External Drivers:

    For now I am using M92 X240 Y204 with no M350 command and all seems good and survives M98 P"config.g".

    That's the correct approach when using external drivers.



  • @fcwilt said in M92 and M350 and External Drivers:

    For now I am using M92 X240 Y204

    Just picking beans, but shouldn't it be

    M92 X205 Y205
    

    X240 was a typo for sure, but 204.75 is closer to 205 than 204.



  • @o_lampe said in M92 and M350 and External Drivers:

    @fcwilt said in M92 and M350 and External Drivers:

    For now I am using M92 X240 Y204

    Just picking beans, but shouldn't it be

    M92 X205 Y205
    

    X240 was a typo for sure, but 204.75 is closer to 205 than 204.

    Thanks for catching that.

    And you are right - I forgot to take into account that 205 is the better number.

    Frederick


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