Digi International is a manufacturer of IoT-enabled devices. One of the products Digi offers is the Digi XBee OEM RF modules. The Digi XBee OEM module allows integrators and manufacturers alike the ability to make their products wireless instead of being wired.
The Digi XBee RF OEM modules require a regulated power supply and a TTL (0 - 3V) level serial interface. Some of the older Digi products, such as the XStream, supported a CMOS (0 - 5V) interface instead. When interfacing between a 5V device such as an Arduino, a level shifter is required.
With a large number of applications using RS232 or RS485/RS422 voltages, Digi offers an "Interface Board" (p/n: XBIB-CU-TH or the older XBIB-R-DEV) that accepts a wide DC voltage range typically between 7 - 12V. The interface board provides the necessary signal level conversion from 3V at the Digi XBee to either RS232 or RS485/422 or USB voltages. This allows the radio modems to connect easily to existing systems.
When connecting the Digi XBee modules to a PC or laptop, we also offer a USB model of the interface boards (p/n: XBIB-CU-TH, XBIB-C-SMT, and XBIB-C-MMT). These USB versions of the boards draw 5V power from the USB port (may require an external power supply) and, with the proper drivers (Windows 98-XP, Windows Vista / 7 64-bit, Windows 8 32-bit and 64-bit, Linux, and OSX), create a virtual COM port in the operating system. This virtual COM port created by the drivers allows a serial-based application to access the RF modules as though it was a standard serial port. This device is best described as a USB-connected serial radio since it is optimized to transport serial port data at baud rates between 2400 to 1Mbps. This is not to be confused with a USB to USB extension cable.
Many OEMs may save costs by making their own interface board designed to exactly meet the specific requirements of their application. This may not include all of the lines needed to perform firmware updates via Digi XCTU or XBee Studio applications. The Digi interface boards are designed to support many operating modes so they can be used in a wide number of applications.
You can find Digi interface boards on the product page here:
https://www.digi.com/products/embedded-systems/digi-xbee/digi-xbee-tools/digi-xbib-c-development-board
We recommend using the Digi XBee interface board as a reference when considering your own interface design - especially for the power conditioning.