Hello!
i use the librem mainly as a development platform, but since i am at it, i wanted to migrate some of my projects to it too…
first of all, none of my UART adapters work with it, they disconnect immediately:
Nov 15 16:47:58 shinji kernel: [19309.422003] usb 1-2: new full-speed USB device number 9 using xhci_hcd
Nov 15 16:47:58 shinji kernel: [19309.601581] usb 1-2: New USB device found, idVendor=10c4, idProduct=ea60, bcdDevice= 1.00
Nov 15 16:47:58 shinji kernel: [19309.601599] usb 1-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
Nov 15 16:47:58 shinji kernel: [19309.601612] usb 1-2: Product: CP2102 USB to UART Bridge Controller
Nov 15 16:47:58 shinji kernel: [19309.601624] usb 1-2: Manufacturer: Silicon Labs
Nov 15 16:47:58 shinji kernel: [19309.601635] usb 1-2: SerialNumber: 0001
Nov 15 16:47:58 shinji mtp-probe: checking bus 1, device 9: “/sys/devices/pci0000:00/0000:00:14.0/usb1/1-2”
Nov 15 16:47:58 shinji mtp-probe: bus: 1, device: 9 was not an MTP device
Nov 15 16:47:58 shinji kernel: [19309.663746] usbcore: registered new interface driver cp210x
Nov 15 16:47:58 shinji kernel: [19309.663830] usbserial: USB Serial support registered for cp210x
Nov 15 16:47:58 shinji kernel: [19309.663975] cp210x 1-2:1.0: cp210x converter detected
Nov 15 16:47:58 shinji kernel: [19309.668853] usb 1-2: cp210x converter now attached to ttyUSB0
Nov 15 16:48:05 shinji kernel: [19317.200074] usb 1-2: usbfs: interface 0 claimed by cp210x while ‘brltty’ sets config #1
Nov 15 16:48:05 shinji kernel: [19317.201352] cp210x ttyUSB0: cp210x converter now disconnected from ttyUSB0
Nov 15 16:48:05 shinji kernel: [19317.201454] cp210x 1-2:1.0: device disconnected
i have 4 different kind of those adapters, thanks to chinese quality and depending on the device to test you need either of them, but none of them work on the librem with similar messages… so well no hardware debugging… 
sooo, now i went over to try to connect some ESD8266 or other Arduinos, no surprise, exactly the same behaviour…
now i took out a fossil out of my collection, a arduino 2009, which definitely doesn’t hit the limits of current drawing from the usb port , but still, i give this last one too:
Nov 15 16:52:39 shinji kernel: [19590.581440] usb 1-6: new full-speed USB device number 10 using xhci_hcd
Nov 15 16:52:39 shinji kernel: [19590.737350] usb 1-6: New USB device found, idVendor=0403, idProduct=6001, bcdDevice= 6.00
Nov 15 16:52:39 shinji kernel: [19590.737400] usb 1-6: New USB device strings: Mfr=1, Product=2, SerialNumber=3
Nov 15 16:52:39 shinji kernel: [19590.737411] usb 1-6: Product: FT232R USB UART
Nov 15 16:52:39 shinji kernel: [19590.737418] usb 1-6: Manufacturer: FTDI
Nov 15 16:52:39 shinji kernel: [19590.737426] usb 1-6: SerialNumber: A800eq3w
Nov 15 16:52:39 shinji kernel: [19590.741266] ftdi_sio 1-6:1.0: FTDI USB Serial Device converter detected
Nov 15 16:52:39 shinji kernel: [19590.741487] usb 1-6: Detected FT232RL
Nov 15 16:52:39 shinji kernel: [19590.753782] usb 1-6: FTDI USB Serial Device converter now attached to ttyUSB0
Nov 15 16:52:39 shinji mtp-probe: checking bus 1, device 10: “/sys/devices/pci0000:00/0000:00:14.0/usb1/1-6”
Nov 15 16:52:39 shinji mtp-probe: bus: 1, device: 10 was not an MTP device
Nov 15 16:52:42 shinji kernel: [19593.392678] usb 1-6: usbfs: interface 0 claimed by ftdi_sio while ‘brltty’ sets config #1
Nov 15 16:52:42 shinji kernel: [19593.394147] ftdi_sio ttyUSB0: FTDI USB Serial Device converter now disconnected from ttyUSB0
Nov 15 16:52:42 shinji kernel: [19593.394240] ftdi_sio 1-6:1.0: device disconnected
is there any hope? what’s going wrong?
ciao
Bruno