Serial adapters/Linux/ModemManager

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Some hosts include a USB modem detector, modemmanager, which opens any newly plugged adapter, configures it for 57600 baud, and transmits AT commands to elicit a response from a modem. This may interfere with use of a serial adapter. There are several workarounds:

  • wait out the delay, and connect the coloured serial cable after starting screen,
  • remove the ModemManager package, permanently preventing probe of USB modems, type this:
sudo rpm -e ModemManager && sudo killall modem-manager
  • add udev rules to exclude the adapter, add this to /etc/udev/rules.d/01-local:
ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6001", ENV{ID_MM_DEVICE_IGNORE}="1"

Affected hosts include:

  • XOs with recent OLPC OS builds,
  • Ubuntu,
  • Debian.