For a Particle Boron, can be used to play with the onboard u-blox modem
Also includes code to change to and from internal and external SIM usage.
To watch modem during connection to a cell tower and then onto Particle Cloud, use the CLI Serial Monitor on the USB port. Have the command at the ready in the CMD window, connect the Boron to the PC's serial port, and press enter as soon as Boron's blue D7 LED lights up. This is to allow catching all the Particle OS's interactions with the modem.