I was so happy to start, that I connected my Lan cable with the maiana Port in the hurry.
Soon after starting it started to smoke at the opposite side of the board.
I can not even say if it was on the hat or the pi, where the smoke came from.
But it seems that nothing was damaged so far.
(Now I've put a tape over the maiana port)
Welcome to the club
Only the diode of the MAIANA TX switch connector should be damaged, the rest will work as expected. If you want to use a MAIANA transponder remove the burned diode and the switch should work again.
Without a doubt this is something that we could improve in the next version and protect this connector from this possible mistake.
We will probably ship the next few batches with some cover or dummy plug to prevent mistakes like this.
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Still thinking about a future circuit revision that makes this mistake less catastrophic. The issue is, that when plugging an Ethernet device into that port while the MacArthur HAT is powered from 12V, the pin where MAIANA excpects 12v will loop back to the pin where MAIANA expects the AIS TX switch. This blows up an ESD protection diode on the MacArthur HAT. The tricky thing is, to apply a fix that's not interfering with the functionality of MAIANA. Increasing the working voltage of the ESD diode from 3.3V to >12V is my current favorite.
Meanwhile, people that already have a MacArthur HAT can make their own dummy plugs by cutting off the connector from an old network cable.