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dc42
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The board I propose will also cost less to manufacture than a Duet, mostly by using a microcontroller with fewer pins and without on-chip Ethernet, leaving off the other Ethernet bits...
Just two posts above you argued in favor of including an Ethernet interface and now you are arguing that to save costs this same Ethernet interface should not be included in your new design?
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dc42
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I'd be reluctant to move anything to a Linux box, because I like the fact that both my Duet-powered printers are ready to be controlled within a second of being powered up.
The small ARM boxes I use as Linux Debian / OctoPrint servers stay on 24/7, their power consumption being approximately the same as the standby power consumption of the ATX PSUs I use for my 3D printers (i.e 2.5W), so as far as "readyness to print after power on" is concerned, they are a non-issue.
So far it seems to me that you are planning your new design basically by making small changes to the Duet design, what I am proposing is to think outside the box and do something different.