I think the Rock5b maybe quite a concrete design already but the mic according to Allnet is Audio 3.5mm jack with mic so its prob a mobile style TRRS type likely where a channel is for a mic.
I think the USB OTG is a limitation of the SoC and that its USB 2.0 only on the RK3588, my memory is bad at times but got it in my head the rk356x is the only one so far with usb3.0 OTG,
12v DC in & out again prob past point of changes but I will open up a discussion for maybe possible future changes.
I haven’t got any concrete solutions but the lack of a 12v bus is likely something that needs addressing and that the onboard 40 pin GPIO grabs a huge amount of space, never has enough pins so its always compromise on what the pin mux presents and always someone loses out to which pin mux is avail.
Also the pin mux and board routing often means its never completely Pi compatible its just this thing that looks Pi like that does something similar, but is never the same.
I have thought for a while higher density connectors such as flexible flat cables would likely make a much better job of distributing pin mux where a 40pin is offboard and merely the terminating connector that can mount on hex pillars if you wish so.
You could have a single 40pin with choice of 2x Flexible ribbons and have a choice of 80 pins from the mux without having to play hardware revision merry-go-round as you just swap the FPC over for a different pin mux or even have different 40 pin connector boards.
That would also likely free up space for DC power connectors also but which and what I dunno, but the connector I often question the most especially when its not 100% Pi compatible is the 40 pin GPIO.
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) … as of right now my $50 rebate feels kind of pointless given its original pricing … I’m saying it’s maybe better for me to wash the $5 cost of the voucher.