A collection of useful USRP utilities

apps directory:

• read_usrp_time: reading the USRP time
• reset_usrp_time: resetting USRP time to 0.0
• rx_timed_samples_to_file: recording samples to a file staring at a known time
• timed_rx_file_mqtt: recording samples to files based on a trigger over mqtt

more complicated application have sample scripts named run_<name>.sh to use them.

scripts directory:

• mqtt_trig.sh: simple mosquitto_pub based script to send a trigger for timed_rx_file_mqtt

Prerequisites

To compile the (important MQTT) application included, we need non-SSL versions of Paho MQTT C, Paho MQTT C++ and UHD installed in some known locations (I install everything to ~/install but it can be changed by changing the DESTDIR in make install and CMAKE_PREFIX_PATH in the cmake command. Note that CMAKE_PREFIX_PATH would have to point to <install dir>/usr/local). The other non-MQTT applications only need UHD installed.

compile and install paho.mqtt.c

Builds the paho C static library and install its to a local ~/install folder.

Note: using a personal fork of the PAHO C and CPP libraries (we were facing some problems with compiling examples for the non-SSL versions earlier)

git clone https://github.com/adwaitnd/paho.mqtt.c.git
mkdir paho.mqtt.c/build
cd paho.mqtt.c/build
cmake -DPAHO_BUILD_STATIC=TRUE -DPAHO_BUILD_SHARED=FALSE -DPAHO_WITH_SSL=FALSE ..
make
make DESTDIR=~/install install

compile and install paho.mqtt.cpp

Builds the paho C++ static library and install it to a local ~/install folder in the home directory. If this is to be changed, make changes to the DESTDIR option in make install.

We're relying on a paho.mqtt.c static library being installed at ~/install/usr/local/. If this is different, make the appropriate changes to CMAKE_PREFIX_PATH option for cmake.

Note: using a personal for of the PAHO C and CPP libraries (we were facing some problems with compiling examples earlier)

git clone https://github.com/adwaitnd/paho.mqtt.cpp.git
mkdir paho.mqtt.cpp/build
cd paho.mqtt.cpp/build
cmake -DCMAKE_PREFIX_PATH=~/install/usr/local -DPAHO_BUILD_STATIC=TRUE -DPAHO_BUILD_SHARED=FALSE -DPAHO_WITH_SSL=FALSE ..
make
make DESTDIR=~/install install

compile and install UHD

Build a custom port of the UHD library and installs it to a local ~/install folder.

git clone https://github.com/WiseLabCMU/uhd.git
mkdir uhd/host/build
cd uhd/host/build
cmake ..
make uhd
make DESTDIR=~/install install

Compiling

git clone https://github.com/adwaitnd/usrp-apps.git
mkdir usrp-apps/build
cd usrp-apps/build
cmake -DCMAKE_PREFIX_PATH=~/install/usr/local ..
make

Use

Timed capture using trigger on MQTT

Example use of timed_rx_file_mqtt (Also found in run_timed_rx_file_mqtt.sh):

timed_rx_file_mqtt --usrpargs="addr=192.168.10.3" --mqttserv="tcp://mqtt.example.com:1883" --id=$(hostname) --prefix="$HOME/Workspace/data/exp0_" --pubtop="usrp/response" --subtop="usrp/command" --ntpslack=0.2

• usrpargs: where to find the USRP device
• mqttserv: where to find the MQTT server. Include protocol and port
• id: name of the computer. used for messaging the MQTT server correctly
• prefix: filename prefix. Can include complete path location
• pubtop: what topic the gateway will send notifications about the request
• subtop: what topic the gateway will use to listen for commands
• ntpslack: how much worst-case offset do we assume between NTP time on gateway host and GPS time on the GPSDO

Timed capture using offset from local time

TODO: instructions for rx_timed_sampled_to file. Look at run_rx_timed_sampled_to file.sh for a quick and dirty reference

Triggering a capture

Message format to send on the MQTT trigger topic to start a capture:

"fc=$fc,lo=$lo,sps=$sps,bw=$ifbw,g=$gain,t0=$trequest,n=$nsamp,ant=$ant"

• fc: center frequency of capture in Hz (double)
• lo: LO offset in Hz (double). generally 0
• sps: samples per second or sample rate (double)
• bw: bandwidth of intermediate frequency filter in Hz (double)
• g: gain of frontend in dB (double)
• t0: exact capture starting time in UTC (double)
• n: number of samples to capture (int)
• ant: antenna to use (string)

Check scripts/mqtt_trig_*.sh for examples on triggering a capture using mosquitto_pub.`

Other

VSCode CMake Tools configurations

If you want to use the Cmake Tools extension for building and debugging, add the following entry in your .vscode/settings.json file

"cmake.configureSettings": {
        "CMAKE_PREFIX_PATH":"~/install/usr/local"
    }

Relevant repositories

• MBED code for transmit-only SX1262 client that is used for experiments [https://github.com/adwaitnd/sx1262-tx] or [https://os.mbed.com/users/adwaitnd/code/SX126X_TXonly/]
• USRP synchronous data capture application [https://github.com/adwaitnd/usrp-apps]
• Tools to analyze USRP LoRa captures and to work with ray tracing simulation outputs [https://github.com/adwaitnd/lpwan-sdr-analysis]