Maestro: Turning a 12864 on/off?



  • Hi,
    I've got an Maestro board, powered by an ATX PSU.
    Currently the 12864 LCD and it's light is permanent turned on, even when the board is powered only by the ATX Standby. This annoys me a little.
    Is there any way to have it only turned on, when ATX is turned on and the board is powered by VIN or to turn it on and off by any Gcode?
    Thanks
    Thomas



  • the standard 12864 hardware does not allow this
    see
    https://github.com/MarlinFirmware/Marlin/issues/4728



  • @tcj said in Maestro: Turning a 12864 on/off?:

    Is there any way to have it only turned on, when ATX is turned on and the board is powered by VIN or to turn it on and off by any Gcode?

    You could rewire the Vcc pin for the 12864 to a 5v fan pin, or maybe the buffered servo output, or an external switch of sorts; but you might find that it then needs to be initialized after being powered on, which the firmware cannot do more than once with the current implementation.

    Another option is to cut the backlight traces and insert a mosfet or something there which you can wire to the duet, should work regardless of firmware support, I intend to do something similar with mine when RRF3 is ready with all the conditional g-code.

    But as it stands it will require hardware modifications, and possibly even changes to the firmware.


  • administrators

    Not easy, but possible. With the display the right way up and looking at it from the front, the leftmost pin in the row at the bottom of the 12864 display module is the backlight LED cathode. You need to disconnect it from the main PCB, for example by sawing through the black spacer and the pin inside it with a hacksaw blade. Or if you heat the pin using SMD heated tweezers on one end and a soldering iron on the other end, you may be able to pull it out with the tweezers. Then connect that pin of the display module to the negative pin of a spare heater or fan output on the Maestro. You could then use the M42 command to control the backlight intensity.

    PanelDue already includes an option to dim the backlight (but not turn it off completely) after a period of inactivity.



  • @dc42 Thank you - that sounds promising - I will try



  • Just realized, that I don't have any free heater or fan output. Could I use EXP0 instead?


  • administrators

    @tcj said in Maestro: Turning a 12864 on/off?:

    Just realized, that I don't have any free heater or fan output. Could I use EXP0 instead?

    You would need to use a small mosfet or NPN transistor + resistor to control the backlight from an expansion pin.


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