[ 2690.566436] usb 5-1: new full-speed USB device number 103 using uhci_hcd
[ 2690.959439] usb 5-1: New USB device found, idVendor=239a, idProduct=8032
[ 2690.959443] usb 5-1: New USB device strings: Mfr=2, Product=3, SerialNumber=1
[ 2690.959445] usb 5-1: Product: Grand Central M4 Express
[ 2690.959447] usb 5-1: Manufacturer: Adafruit Industries LLC
[ 2690.959449] usb 5-1: SerialNumber: 546586EE3353533502020243E3E0xxxx
[ 2690.964492] cdc_acm 5-1:1.0: ttyACM0: USB ACM device
[ 2690.969479] usb-storage 5-1:1.2: USB Mass Storage device detected
[ 2690.969852] scsi host6: usb-storage 5-1:1.2
[ 2690.979633] input: Adafruit Industries LLC Grand Central M4 Express as /devices/pci0000:00/0000:00:1a.2/usb5/5-1/5-1:1.3/0003:239A:8032.02DF/input/input751
[ 2691.039135] hid-generic 0003:239A:8032.02DF: input,hidraw3: USB HID v1.11 Keyboard [Adafruit Industries LLC Grand Central M4 Express] on usb-0000:00:1a.2-1/input3
[ 2691.039227] usb 5-1: USB disconnect, device number 103
The disconnecting will continue to loop. (See last line of dmesg output. 103 and going). I have two boards and both have the same problem. Using Arduino IDE. I can program other boards with no problems. It's just this board disconnects. I don't know why it's disconnecting. Does anyone have udev rule for this board? Or our you having the same problem?
Some Grand Central boards were shipped with the on-board crystal installed upside down. See pictures in this post: viewtopic.php?f=63&t=152105&p=750925#p750925. This can mess up the USB timing. Take a look at your board and see if that's the issue.
If not (if crystal is installed correctly):
What is the host computer you're using? Is it a PC (x64) or is it some other Linux board?
Other boards are Arduino Due R3, Adafruit Arduino Pro Mini, Gameduino 3, etc... The the on-board crystal is OK. The problem is only with Metro Grand Central connecting and disconnecting loop.
I can get the board to connect to Linux by holding down the reset button. (30 sec or maybe longer) Then NeoPixel will be solid green, the L - Red LED will be a slow glowing pulse and ON led will be green. The storage will show as GCM4BOOT with 3 files: CURRENT.UF2 INDEX.HTM and INFO_UF2.TXT The board is connected to the system /dev/ttyACM0 and we have access to storage GCM4BOOT. It looks like the board is not running the default program with NeoPixel light changing colors. I don't know what state the board is in, but think this boot load/access mode. For Linux user make sure to umount the Metro storage device before discounting the USB (Power Off).
So far this is the only way I can get to board stop the loop of connecting and discounting. It looks like maybe a problem with the storage on the board and Linux. Maybe disabling the storage connecting with udev rule may solve the problem. When I get some more time I will try to upload a program.
Once you see GCM4BOOT, try loading Blink or something simple on the board. Make sure the board is set in Arduino to Grand Central, and make sure the Adafruit SAMD board support package up to date.
