title: Connect usb scale in Ubuntu, cdc_acm says failed to set dtr/trs
body: <p>I am trying to connect an scale (Dibal series 400) in Linux (Ubuntu), and I can not succeed. The scale works on Windows after installing a driver to enable a Virtual Com Port, but when I plug in the scale in Linux, it tries to start, but after a while the scale is power down.</p>
  
  <p>The sys log messages says:</p>
  
  <pre><code>kernel: [ 3202.896355] usb 1-2: new full-speed USB device number 8 using xhci_hcd
  kernel: [ 3203.038395] usb 1-2: New USB device found, idVendor=0483, idProduct=5740
  kernel: [ 3203.038400] usb 1-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
  kernel: [ 3203.038403] usb 1-2: Product: Dibal G Series
  kernel: [ 3203.038405] usb 1-2: Manufacturer: DIBAL S.A
  kernel: [ 3203.038407] usb 1-2: SerialNumber: 00000000001A
  kernel: [ 3203.039349] cdc_acm 1-2:1.0: ttyACM0: USB ACM device
  mtp-probe: checking bus 1, device 8: "/sys/devices/pci0000:00/0000:00:14.0/usb1/1-2"
  mtp-probe: bus: 1, device: 8 was not an MTP device
  kernel: [ 3203.081110] [UFW BLOCK] IN=wlp2s0 OUT= MAC= SRC=fe80:0000:0000:0000:8bb6:c943:d1eb:b07f DST=ff02:0000:0000:0000:0000:0000:0000:0001 LEN=64 TC=0 HOPLIMIT=1 FLOWLBL=400724 PROTO=UDP SPT=8612 DPT=8612 LEN=24 
  kernel: [ 3203.081125] [UFW BLOCK] IN=wlp2s0 OUT= MAC= SRC=fe80:0000:0000:0000:8bb6:c943:d1eb:b07f DST=ff02:0000:0000:0000:0000:0000:0000:0001 LEN=64 TC=0 HOPLIMIT=1 FLOWLBL=123875 PROTO=UDP SPT=8612 DPT=8610 LEN=24 
  kernel: [ 3203.091404] [UFW BLOCK] IN=wlp2s0 OUT= MAC= SRC=fe80:0000:0000:0000:8bb6:c943:d1eb:b07f DST=ff02:0000:0000:0000:0000:0000:0000:0001 LEN=64 TC=0 HOPLIMIT=1 FLOWLBL=400724 PROTO=UDP SPT=8612 DPT=8612 LEN=24 
  kernel: [ 3203.091423] [UFW BLOCK] IN=wlp2s0 OUT= MAC= SRC=fe80:0000:0000:0000:8bb6:c943:d1eb:b07f DST=ff02:0000:0000:0000:0000:0000:0000:0001 LEN=64 TC=0 HOPLIMIT=1 FLOWLBL=123875 PROTO=UDP SPT=8612 DPT=8610 LEN=24 
  kernel: [ 3207.543042] usb 1-2: USB disconnect, device number 8
  kernel: [ 3207.543169] cdc_acm 1-2:1.0: failed to set dtr/rts
  ModemManager[1005]: &lt;warn&gt;  (ttyACM0) could not open serial device (2)
  ModemManager[1005]: &lt;warn&gt;  (Plugin Manager) (Nokia) [ttyACM0] error when checking support: '(tty/ttyACM0) failed to open port: Could not open serial device ttyACM0: No such file or directory'
  ModemManager[1005]: &lt;warn&gt;  (ttyACM0) could not open serial device (2)
  ModemManager[1005]: &lt;warn&gt;  (Plugin Manager) (Iridium) [ttyACM0] error when checking support: '(tty/ttyACM0) failed to open port: Could not open serial device ttyACM0: No such file or directory'
  ModemManager[1005]: &lt;warn&gt;  (ttyACM0) could not open serial device (2)
  ModemManager[1005]: &lt;warn&gt;  (Plugin Manager) (Cinterion) [ttyACM0] error when checking support: '(tty/ttyACM0) failed to open port: Could not open serial device ttyACM0: No such file or directory'
  ModemManager[1005]: &lt;warn&gt;  (ttyACM0) could not open serial device (2)
  ModemManager[1005]: &lt;warn&gt;  (Plugin Manager) (Generic) [ttyACM0] error when checking support: '(tty/ttyACM0) failed to open port: Could not open serial device ttyACM0: No such file or directory'
  ModemManager[1005]: &lt;info&gt;  Couldn't find support for device at '/sys/devices/pci0000:00/0000:00:14.0/usb1/1-2': not supported by any plugin
  </code></pre>
  
  <p>As additional information, in Windows it is recognized as:</p>
  
  <p>STMicroelectronics Virtual COM Port (COM3)
  And it has the next configuration:
  Baudrate: 9600
  Parity: None</p>
  
  <p>While the scale is starting (the 3 or 4 secs that keeps running), I have tested:</p>
  
  <p>udevadm test /sys/devices/pci0000:00/0000:00:14.0/usb1/1-1</p>
  
  <pre><code>ACTION=add
  BUSNUM=001
  DEVNAME=/dev/bus/usb/001/036
  DEVNUM=036
  DEVPATH=/devices/pci0000:00/0000:00:14.0/usb1/1-1
  DEVTYPE=usb_device
  DRIVER=usb
  ID_BUS=usb
  ID_MODEL=Dibal_G_Series
  ID_MODEL_ENC=Dibal\x20G\x20Series
  ID_MODEL_FROM_DATABASE=STM32F407
  ID_MODEL_ID=5740
  ID_REVISION=0200
  ID_SERIAL=DIBAL_S.A_Dibal_G_Series_00000000001A
  ID_SERIAL_SHORT=00000000001A
  ID_USB_INTERFACES=:020201:0a0000:
  ID_VENDOR=DIBAL_S.A
  ID_VENDOR_ENC=DIBAL\x20S.A
  ID_VENDOR_FROM_DATABASE=STMicroelectronics
  ID_VENDOR_ID=0483
  MAJOR=189
  MINOR=35
  PRODUCT=483/5740/200
  SUBSYSTEM=usb
  TYPE=0/0/0
  USEC_INITIALIZED=9445077321
  Unload module index
  Unloaded link configuration context.
  </code></pre>
  
  <p>Could anyone help me?</p>
  
  <p>Thank you very much, 
  Javi. </p>