Configuring Bluetooth LE devices for Direct Test Mode

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1 Requirements

Requirements for programming the DUT:

One of the utilities below:
A Simplelink™Launchpad™ or standalone JTAG Debug Probe
The Simplelink™ Software Development Kit (SDK):
- CC13x2 and CC26x2
- CC2640R2

Requirements for testing:

A Computer running Windows® 7 or 10.
CBT and CBT32 Tester
- The analyzer is CBT and the attenuator is CBT32.
R&S® CBTGo software
The DUT (Device Under Test) furnished with a coaxial connector to be plugged to the test system.
A GPIB card or USB accessory and the appropriate GPIB cable to connect to the CBT tester. This procedure used a National Instruments® GPIB-USB-HS interface.
A RS232 voltage translator accessory. This is very important. The voltages on the RS232 port in the back of the CBT tester are high and will damage your DUT.
A Straight RS232 cable (not null modem) - typically female connector (to connect on the back port of the CBT tester) and a male connector (to connect on the RS232 voltage translator).

2 Testing overview

The overall setup to perform Bluetooth Low Energy using the CBT Bluetooth tester is shown in the diagram below.

Note: Although the procedure shows the CBT tester, the principles of operation and connections can be easily leveraged to other testers such as the CMW270, for example.

The CBT Bluetooth tester (Figure 2-1 shows two views: rear and front panels) connects to both a PC and the Device Under Test (DUT), which is a custom board or a development kit such as the Launchpad.

Figure 2-1 The test setup

The PC runs the CBTGo software and connects to the CBT via a General Purpose Interface Bus (GPIB) interface to control and configure it to perform the tests. It also gathers the test results for printing and sharing.

Note: The CBT can also be remotely controlled via GPIB. However, to test Bluetooth Low Energy devices, the RS232 port must be used to control the DUT, therefore only leaving the GPIB available to be connected.

The CBT connects to the DUT in two ways: a RF connection to transmit the Bluetooth data to the DUT and a RS232 connection to communicate with the DUT and perform control and gather packet data and statistics.

The DUT must have a software that exposes a communications interface to interact with the CBT. This can be accomplished by adding the Direct Test Mode (DTM) functionality to the application or use an application specifically designed for DTM.

The out-of-the-box host_test project, provided with the Simplelink SDK, is a complete HCI-enabled software that allows DTM to operate in a transparent manner through a UART port. For a Simplelink Launchpad, the UART port is the XDS110 secondary channel port (the one not used by the XDS110 JTAG functionality).

A discussion about enabling DTM on an end application is outside of the scope of this application note, but additional details about the DTM and HCI test modes can be found at the BLE5 Stack User's Guide chapter BLE5-Stack → Host Controller Interface (HCI)

To perform the testing, two setup procedures will be described in the next steps: program the DUT with the out-of-the-box host_test, install the control software and perform the hardware connections.