GPIO pins in expansion header?

  • General GPIO / PWM pins available?

    I am switching from a RAMPs board to a DuetWifi, have most of the printer related stuff working, minus the bed heater, which I posted about in another thread.

    On the RAMPs I used 3 GPIO PWM pins to drive 3 IRF3708 mosfets which in turn control a string of common anode RGB leds. Would like to use the same setup on my DuetWifi.

    I see the expansion header but it appears those pins are already spoken for. Is it possible to use them for GPIO PWM instead? If so, is there a pinout I can use to map a M42 gcode to?

    If there is not, is it possible to have messages sent out via SPI via gcode? I am looking at some SPI controlled PWM boards from Adafruit that might just be the ticket if GPIO pins are not available.

  • administrators

    All the hardware-PWM-capable output pins are assigned to heaters and fans. Currently you can't reassign the heater pins without recompiling the firmware, because the associated PIDs are liable to overwrite anything you write to them. I intend to introduce an M code that would let you specify now many heaters you have, thereby allowing the remaining heater pins to be used as GPIO pins.

    The Duet WiFi expansion boards we are working on will also provide additional PWM channels.

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