Driver for USB-to-serial adaptors

Note: You must be root or have the right abilities to start this driver.


devc-serusb_dcd [options]

Runs on:

QNX Neutrino


ARMLE-v7, x86


-b baudrate
The initial baud rate. The supported baud rates are 75, 150, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200, 38400, 57600 (the default), 115200, 230400, and 460800.
-C size
The size of the canonical buffer, in bytes (default 256).
-d args[,args ...]
Device-specific options; see Device-specific options,” below.
Set options to “raw” (default).
Start in edited mode (default raw). Software flow control is enabled by default.
Disable hardware flow control (default to hardware flow control enabled). Hardware flow control isn't supported in edited mode.
Enable hardware flow control (default). Hardware flow control isn't supported in edited mode.
-I number
The size of the raw input buffer in bytes (default 2048).
-O number
(“Oh”) The size of the output buffer, in bytes (default 1536).
-o opt[,opt]...
(“oh”) A comma-separated list of additional options:
  • nodaemon — don't run in the background.
  • priority=prio — set the working priority of the internal pulse.
Disable / enable software flow control. The default depends on the mode: in raw mode (-E, the default), it's disabled; in edited mode (-e), it's enabled.

The order in which you specify the -E or -e, and -S or -s options matters:

Options Mode Software flow control
-e Edited Enabled
-S -e Edited Enabled
-e -S Edited Disabled
-E Raw Disabled
-s -E Raw Disabled
-E -s Raw Enabled
Be verbose; additional v characters cause more verbosity.

Device-specific options

The device-specific options that you can specify with the -d option are:

The device ID of the serial device.
Specify the USB interface number of the Communications class interface index. This option also causes the driver to immediately create a /dev/serusbX entry before the device is accessible to the host.
Connect to the specified USB stack. The default is /dev/usb/io-usb-otg.
Set the port index for subsequent port-specific options.
Set the priority of the Rx, Tx, and USB stack events. The default priority is 21.
The USB transfer size. The default is the bulk endpoints' maximum packet size, typically 512; the buffer size is rounded up to the nearest multiple of 512.
The vendor ID of the serial device.


The devc-serusb_dcd is a driver for USB-to-serial adaptors, which in combination with the USB device stack (io-usb-otg), supports a CDC (Communications Device Class) interface presented to a connected USB host.

Note: The io-usb-otg server must be running before you start this driver.

This driver creates a /dev/serusbX entry in the pathname space, where X is the next available integer, starting from 1. This happens when the device becomes accessible to the host, unless you specify the iface_list option, in which case it happens immediately.


The devc-serusb_dcd driver may require the following abilities:

Use secpolmonitor to determine which abilities devc-serusb_dcd is using on your specific system.

For more information on abilities, see procmgr_ability() in the C Library Reference.


Start the driver with edited mode enabled, verbosity enabled, HW and SW flow control disabled, and a USB index of 0 (which also immediately reserves the /dev/serusbX path):

devc-serusb_dcd -e -v -F -s -d iface_list=0