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I am using an Arduino MEGA connected to my Linux workstation via USB. I have been using this setup for several months with no issues.

A few days ago, the usual serial device file (/dev/ttyACM0) stopped showing up when I plug in the device)

  • Haven't re-flashed recently.
  • Unable to reflash.
  • Removing the devices only shield does not do anything.
  • Have not changed my physical setup recently.
  • Connector cable is confirmed working with a different device.

Is this a case of bad hardware, or is there a possible fix other than buying a new device?

dmesg results: None (cleared buffer and re-ran dmesg after plugging / unplugging device) usb-devices:

T:  Bus=01 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=480 MxCh= 2
D:  Ver= 2.00 Cls=09(hub  ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=1d6b ProdID=0002 Rev=03.13
S:  Manufacturer=Linux 3.13.0-37-generic ehci_hcd
S:  Product=EHCI Host Controller
S:  SerialNumber=0000:00:1a.0
C:  #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=0mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub

T:  Bus=01 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#=  2 Spd=480 MxCh= 6
D:  Ver= 2.00 Cls=09(hub  ) Sub=00 Prot=01 MxPS=64 #Cfgs=  1
P:  Vendor=8087 ProdID=0024 Rev=00.00
C:  #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=0mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub

T:  Bus=02 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=480 MxCh= 2
D:  Ver= 2.00 Cls=09(hub  ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=1d6b ProdID=0002 Rev=03.13
S:  Manufacturer=Linux 3.13.0-37-generic ehci_hcd
S:  Product=EHCI Host Controller
S:  SerialNumber=0000:00:1d.0
C:  #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=0mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub

T:  Bus=02 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#=  2 Spd=480 MxCh= 6
D:  Ver= 2.00 Cls=09(hub  ) Sub=00 Prot=01 MxPS=64 #Cfgs=  1
P:  Vendor=8087 ProdID=0024 Rev=00.00
C:  #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=0mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub

T:  Bus=02 Lev=02 Prnt=02 Port=03 Cnt=01 Dev#=  3 Spd=480 MxCh= 0
D:  Ver= 2.00 Cls=ef(misc ) Sub=02 Prot=01 MxPS=64 #Cfgs=  1
P:  Vendor=1bcf ProdID=2805 Rev=20.15
S:  Manufacturer=6047B0021601A0218M7NB
S:  Product=HP HD Webcam [Fixed]
C:  #Ifs= 2 Cfg#= 1 Atr=80 MxPwr=500mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=0e(video) Sub=01 Prot=00 Driver=uvcvideo
I:  If#= 1 Alt= 0 #EPs= 0 Cls=0e(video) Sub=02 Prot=00 Driver=uvcvideo

T:  Bus=02 Lev=02 Prnt=02 Port=05 Cnt=02 Dev#=  4 Spd=12  MxCh= 0
D:  Ver= 2.00 Cls=e0(wlcon) Sub=01 Prot=01 MxPS=64 #Cfgs=  1
P:  Vendor=0bda ProdID=0001 Rev=68.17
S:  Product=CSR BS8510
C:  #Ifs= 2 Cfg#= 1 Atr=e0 MxPwr=0mA
I:  If#= 0 Alt= 0 #EPs= 3 Cls=e0(wlcon) Sub=01 Prot=01 Driver=btusb
I:  If#= 1 Alt= 0 #EPs= 2 Cls=e0(wlcon) Sub=01 Prot=01 Driver=btusb

T:  Bus=03 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=480 MxCh= 2
D:  Ver= 2.00 Cls=09(hub  ) Sub=00 Prot=01 MxPS=64 #Cfgs=  1
P:  Vendor=1d6b ProdID=0002 Rev=03.13
S:  Manufacturer=Linux 3.13.0-37-generic xhci_hcd
S:  Product=xHCI Host Controller
S:  SerialNumber=0000:26:00.0
C:  #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=0mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub

T:  Bus=04 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=5000 MxCh= 2
D:  Ver= 3.00 Cls=09(hub  ) Sub=00 Prot=03 MxPS= 9 #Cfgs=  1
P:  Vendor=1d6b ProdID=0003 Rev=03.13
S:  Manufacturer=Linux 3.13.0-37-generic xhci_hcd
S:  Product=xHCI Host Controller
S:  SerialNumber=0000:26:00.0
C:  #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=0mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub

ls-usb:

Bus 002 Device 004: ID 0bda:0001 Realtek Semiconductor Corp. 
Bus 002 Device 003: ID 1bcf:2805 Sunplus Innovation Technology Inc. 
Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
  • Please give us any relevant output from dmesg and also lsusb and usb-devices – Majenko May 11 '15 at 12:41
1

The fact that dmesg gives you nothing at all is the most telling fact. The there was a communication problem, or the firmware had messed up on the USB interface chip, then you'd expect something to show up - even if it was something along the lines of "device not accepting address 8: -71"

We can ignore the main ATMega2560 chip since that has no bearing on the USB interface. Instead we're interested in the ATMega16U2 (or whatever is on your board version).

So some things you need to confirm by probing around on the board with a multimeter, or better still, an oscilloscope:

  1. Check that there is power to the board through the USB.
  2. Check that there is power both sides of the green (or brown-ish if you have a clone) poly-fuse near the USB socket
  3. If you have an oscilloscope, switch the probe to 10x and look for oscillations on the crystal's pins.
  4. Grab the datasheet for your ATMegaxxU2 chip and get the pinout. Check that there is power on the pins there should be power on.
  5. Check that the RESET pin of the ATMegaxxU2 chip is HIGH.

If you have a hardware programmer, or another Arduino you can use as a hardware programmer, connect it to the 2x3 header (you may need to populate it first) and try get it to identify the chip ID. Try to re-flash the USB interface firmware.

Another thing to check is the USB socket itself. Those big chunky USB sockets look strong, but they're actually quite flimsy inside. The metal leaves that the plug presses against can bend with time and not make a good contact. Using a fine needle try lifting them up slightly so they make better contact with the cable. I think Arduino are the only people that still use them in an active product these days ;)

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