Bluetooth Core Specification

The setup consists of a device under test (DUT) and a tester. Optionally, additional measurement equipment may be used.

Figure 1.1: Setup for Test mode

Tester and DUT form a piconet where the tester acts as Central and has full control over the test procedure. The DUT acts as Peripheral.

The control is done via the air interface using LMP commands (see [Vol 2] Part C, Section 4.7.3). Hardware interfaces to the DUT may exist, but are not subject to standardization.

The test mode is a special state of the Bluetooth model. For security and type approval reasons, a Bluetooth device in test mode shall not support normal operation. When the DUT leaves the test mode it enters the standby state. After power-off the Bluetooth device shall return to the standby state.

The Bluetooth device transmits a constant bit pattern. This pattern is transmitted periodically with packets aligned to the Peripheral TX timing of the piconet formed by tester and DUT. The same test packet is repeated for each transmission.

The transmitter test is started when the Central sends the first POLL packet. In non-hopping mode the agreed frequency is used for this POLL packet.

The tester (Central) transmits control or POLL packets in the Central-to-Peripheral transmission slots. The DUT (Peripheral) shall transmit packets in the following Peripheral-to-Central transmission slot. The tester’s polling interval is fixed and defined by the LMP_TEST_CONTROL PDU. The device under test may transmit its burst according to the normal timing even if no packet from the tester was received. In this case, the ARQN bit is shall be set to NAK.

The burst length may exceed the length of a one slot packet. In this case the tester may take the next free Central TX slot for polling. The timing is illustrated in Figure 1.2.

Figure 1.2: Timing for transmitter test

1.1.2.1. Packet format

The test packet is a normal Bluetooth packet, see Figure 1.3. For the payload itself see below.

Figure 1.3: General format of TX packet

During configuration the tester defines:

• the packet type to be used

• payload length

For the payload length, the restrictions from the Baseband specification shall apply (see [Vol 2] Part B, Section 6.5). In case of ACL, SCO and eSCO packets the payload structure defined in the Baseband specification is preserved as well, see Figure 1.3.

For the transmitter test mode, only packets without FEC should be used; i.e. HV3, EV3, EV5, DH1, DH3, DH5, 2-EV3, 2-EV5, 3-EV3, 3-EV5, 2-DH1, 2-DH3, 2-DH5, 3-DH1, 3-DH3, 3-DH5 and AUX1 packets.

In transmitter test mode, the packets exchanged between the tester and the DUT shall not be scrambled with the whitening sequence. Whitening shall be turned off when the DUT has accepted to enter the transmitter test mode, and shall be turned on when the DUT has accepted to exit the transmitter test mode, see Figure 1.4. Implementations shall ensure that retransmissions of the LMP_ACCEPTED messages use the same whitening status as used in the original LMP_ACCEPTED.

Figure 1.4: Use of whitening in Transmitter mode

1.1.2.2. Pseudorandom sequence

The same pseudorandom sequence of bits shall be used for each transmission (i.e. the packet is repeated). A PRBS9 sequence is used, see [1] and [2].

The properties of this sequence are as follows (see [2]). The sequence may be generated in a nine-stage shift register whose 5th and 9th stage outputs are XORed (see Figure 1.5), and the result is fed back to the input of the first stage. The sequence begins with the first ONE of 9 consecutive ONEs; i.e. the shift register is initialized with nine ones.

• Number of shift register stages:            9

• Length of pseudo-random sequence:   2⁹-1 = 511 bits

• Longest sequence of zeros:                  8 (non-inverted signal)

Figure 1.5: Linear feedback shift register for generation of the PRBS sequence

In loopback, the device under test receives normal Baseband packets containing payload Accepted from the tester. The received packets shall be decoded in the DUT, and the payload shall be sent back using the same packet type. The return packet shall be sent back in either the Peripheral-to-Central transmission slot directly following the transmission of the tester, or it is delayed and sent back in the Peripheral-to-Central transmission slot after the next transmission of the tester (see Figure 1.7 to Figure 1.9).

There is no signaling to determine or control the mode. The device behavior shall be fixed or adjusted by other means, and shall not change randomly.

The tester can select whether whitening is on or off. This setting holds for both uplink and downlink. For switching the whitening status, the same rules as in Section 1.1.2 ( Figure 1.4) shall apply.

The following rules apply (for illustration see Figure 1.6):

Figure 1.6: DUT packet handling in loopback test

The timing for normal and delayed loopback is illustrated in Figure 1.7 to Figure 1.9:

Figure 1.7: Payload and ARQN handling in normal loopback

Figure 1.8: Payload and ARQN handling in delayed loopback – start

Figure 1.9: Payload and ARQN handling in delayed loopback – end

The whitening is performed in the same way as it is used in normal Active mode.

The following parameters can be set to configure the loop back test:

The switch of the frequency setting is done exactly as for the transmitter test (see Section 1.1.2.5).

Pause test is used by testers to put the device under test into Pause Test mode from either the loopback or transmitter test modes.

When an LMP_TEST_CONTROL PDU that specifies Pause Test is received the DUT shall stop the current test and enter Pause Test mode. In the case of a transmitter test this means that no more packets shall be transmitted. While in Pause Test mode the DUT shall respond normally to POLL packets (i.e. responds with a NULL packet). The DUT shall also respond normally to all the LMP packets that are allowed in test mode.

When the test scenario is set to Pause Test all the other fields in the LMP_TEST_CONTROL PDU shall be ignored. There shall be no change in hopping scheme or whitening as a result of a request to pause test.