Z axis motion flipped after disconnecting 1XD board
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Hi,
For a while now I've noticed that the Z axis on my printer occasionally moves in the wrong direction on startup, which has led to the printhead smashing into the bed a few times. I'm running a Duet MB6HC with a 1XD board controlling an external stepper. The mainboard controls the X and Y axes while the 1XD controls the Z axis. After a bit of debugging I've found that this issue happens when my board is connected to the computer over USB.
Disconnecting power to the printer ends up turning off the 1XD, but not the 6HC, which still receives 5V over USB. If I then reconnect power, the default direction for the external stepper is incorrect. Because the 6HC has not been powered off, it doesn't rerun the config file. Manually sending the appropriate M569 command restores the correct Z-axis direction.
How can I solve this issue? I think the right way to do this would be for the 6HC to send the appropriate commands to the 1XD when it first connects to it, but this doesn't seem to be the default behavior.
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After thinking about this a bit more, it seems like the only existing solution to this issue is cutting open the USB cable and removing the 5V input to the Duet; this would ensure the board turns off when I turn the printer off.
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Re-running config.g with M98 P"config.g" when you resume operation of the printer would also work.
