USRP Hardware Driver and USRP Manual  Version:
UHD and USRP Manual
Configuration Files

For permanent configuration of certain device behaviours, UHD supports configuration files.

Format of the configuration files

Configurations files use the INI format. A UHD configuration file might look like this:

; Comments start with a semicolon
; Sections are put in square brackets:
; These settings apply to all USRPs that are of type b200:
; These settings apply to the USRPs with the given serial:
master_clock_rate=10e6 ; If this is a b200, this will overwrite the above settings

Configuring USRPs

For the most part, any setting that can get put into device args at initialization time can be put into the config file. For example, the X300 has a key called ext_adc_self_test which is disabled by default. To enable it, you can add it to your device args:

auto usrp = uhd::usrp::multi_usrp::make("type=x300,ext_adc_self_test=1");

However, this can be cumbersome if the intention is to permanently enable this for all X300s connected to this machine. To generally enable this option for all X300s without having to modify the make() call, the config file can simply be updated as such:


This will act as if this key/value pair had been passed to the device args directly.

Location of configuration files

UHD will look for up to three configuration files:

  1. A system-wide configuration file. On Unix systems, the default location for this file is /etc/uhd/uhd.conf. On Windows systems, %programdata%/uhd/uhd.conf. The default can be overwritten at compile time by setting UHD_SYS_CONF_FILE through CMake.
  2. A user-specific configuration file. On Unix systems, it defaults to $XDG_CONFIG_HOME/uhd.conf, where $XDG_CONFIG_HOME is usually the same as $HOME/.config. On Windows systems, it also checks %localappdata% and %appdata%. The default can be overwritten at compile time by setting the UHD_USER_CONF_FILE through CMake.
  3. A configuration file specified by the environment variable UHD_CONFIG_FILE

UHD will read these files in this order (if they exist). Settings from one file will overwrite those from a previous one, so if the same setting exists in the system-wide file and the user-specific file, the settings from the user-specific file will take effect. There is no error if a file does not exist, or the environment variable is not set.

MPM will only look for a configuration file in /etc/uhd/mpm.conf, on the device running MPM itself.