The datasheet of the F-Carrier (1.3) states that ATTN and F_EN are “shared”. Now maybe you imply something different with “shared”, but I interpret this as “they are connected”. Which they are not.
I think they should be, because if connected, the card.attn-API would just automatically control the power of the connected Feather. Adding a DuPont-jumper wire fixes this, but this not an elegant solution.
Hi,
There is a dip switch on the Notecarrier-F which is labeled “Feather EN” and setting this to N_ATTN will connect the ATTN pin to the EN pin of the Notecarrier regulator which controls power to the Feather headers. In that sense you are correct in saying that you dont get contact between F_EN and ATTN.
However you are able to completely power down the feather using ATTN pin via the regulator which powers the feather headers.
Does that make sense ?
BR,
Serge
Oh thanks. Now that you mention this switch, I can actually see it 
How do I operate this switch? It seems there is a protective foil, I probably have to remove that?!
During my tests, I am connected using the Feather-USB (which does provide power), so I did not notice that ATTN powers down the complete device. I will have to retest. In this case, the connection to F_EN is actually not necessary.
Anyhow, I think both infos are important and should be added to the datasheet.
Hi,
How do I operate this switch? It seems there is a protective foil, I probably have to remove that?!
You can remove the foil or simply move the switch with a pin or small screwdriver.
During my tests, I am connected using the Feather-USB (which does provide power), so I did not notice that ATTN powers down the complete device.
Yes for ATTN to power down the feather you cannot power the feather board directly. If you need to debug via serial port you can connect a TTL converter to F_TX and F_RX and use that. If you need to use the serial port for a sensor, with the Swan (any maybe others) you have a second UART on pins D12 and D13.
Thanks,
Serge