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BLTouch on UM2+ : got it working on Marlin bugfix 1.1.x but hotend fan won't spin up

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Posted · BLTouch on UM2+ : got it working on Marlin bugfix 1.1.x but hotend fan won't spin up

Recently upgraded my UM2+ to BLTouch for auto bed levelling, with Marlin bugfix 1.1.x firmware.

Auto bed levelling works fine, but the hotend fan won't spin up after the hotend reaches and exceeds the trigger temperature. 

I know the fan itself works and is hooked up correctly because I re-uploaded the stock UM2+ firmware and watched it correctly spin the fan when hotend heated up. 


Been all through the firmware and can't find where it references the hotend fan pin on J34 (PJ6).   I've even been through the UM2 original firmware and can't find that pin referenced anywhere either.  


Any ideas what could be wrong?



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    Posted · BLTouch on UM2+ : got it working on Marlin bugfix 1.1.x but hotend fan won't spin up

    Howdy Tinkergnome, thanks for the speedy reply.  I figured it had to be hardwired somewhere.  I will give that a shot.


    Any chance the tinkergnome firmware could be augmented to support BLTouch?  That firmware is my preference to run on a farm of UM2+ printers.  

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    Posted (edited) · BLTouch on UM2+ : got it working on Marlin bugfix 1.1.x but hotend fan won't spin up

    Is there some trick to getting that code to work?  Have added the UM2 specific code into temperature.cpp to set the PORTJ register but no joy.  hotend fan still inoperative.  I am thinking of just hot-wiring the fan to +5V and let it spin continuously.  That's the electrical engineer's solution to a software problem. 😎


    DDRJ |= _BV(6);
      if (current_temperature[0] > EXTRUDER_AUTO_FAN_TEMPERATURE
      #if EXTRUDERS > 1
      || current_temperature[1] > EXTRUDER_AUTO_FAN_TEMPERATURE
      #if EXTRUDERS > 2
      || current_temperature[2] > EXTRUDER_AUTO_FAN_TEMPERATURE
      PORTJ |= _BV(6);
      PORTJ &=~_BV(6);


    Edited by lowracer
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