Test mode

[Shalom Gerbi]

Hi 

We are currently in the midst of our production process and are utilizing a microcontroller that communicates with a BLE chip.
As part of our quality assurance, we aim to test the Tx mode and the Rx sensitivity using UART.

To proceed with this, we require guidance on the specific commands that need to be sent to the BLE chip to initiate the test mode.
Could you please provide us with the following information:

• The exact commands to send from the MCU to the BLE to start the Tx and Rx tests.
• The pattern of data that should be transmitted for the Tx test.
• The methodology for measuring Rx sensitivity.

[ketiljo]

The best approach is to use DTM and a Bluetooth tester here, unless you can do a automated test setup in Labview for instance.

DTM can be found here: https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/samples/bluetooth/direct_test_mode/README.html

[Shalom Gerbi]

Thank you. I have reviewed this document, but I'm finding it difficult to understand what we should do if we want to test it. I only see the commands listed.

As I explained earlier, we want to test it in production by sending commands over the UART and getting back the results. Let me clarify:

We have a controller that manages all the BLE activity, and we want to test the transmission chain. Specifically, we want to:

1. Send a command over the UART.
2. Connect the antenna to a power meter or spectrum analyzer to measure the output power.
3. Test the sensitivity by sending a signal to the antenna and receiving back the BER (Bit Error Rate).

From this document, I am having trouble understanding which commands to send and in what order. Could you please provide more detailed instructions or examples?

[ketiljo]

DTM uses a defined command set over UART. You can find the details in the Bluetooth Corespec. https://www.bluetooth.com/specifications/core-html/ volume 6, part F

It's meant only to be used by a Bluetooth tester. If you don't have that, you can use radio test instead: https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/samples/peripheral/radio_test/README.html

Testing sensitiivity isn't straigth forward here. If you use a nRF devices (a DK) as the tester (TX) you can use the command "start_tx_modulated_carrier" and the number of packets (e.g. 1500) and count the number of received packets on DUT. You can then calculate the PER (packet error rate). 

Maybe you can use a fixed level in a production test and just verify that PER is ok, compared with a golden sample. 

 

[Shalom Gerbi]

I still find it difficult to understand how to test this in production. Do you have a detailed Protocols API? The document is very messy and does not explain the process clearly. It doesn't specify the order of steps, what is needed, or how to proceed.

[ketiljo]

Do you have a Bluetooth tester you intend to use in production? What equipment and instuments do you plan to use?

[Shalom Gerbi]

1. Measuring the output power via spectrum.
2. Receiving packet error information.

These commands will be sent over UART from my controller,

Could you please provide the steps to enter BLE test mode

[ketiljo]

For DTM, see the Bluetooth Core spec. There are no better info. 

For radio test, see https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/samples/peripheral/radio_test/README.html

Do you have a Bluetooth tester you intend to use in production? What equipment and instuments do you plan to use?

[Shalom Gerbi]

Hi 
Thank you for the assistance with the BLE Direct Test Mode setup.
I have successfully tested the configuration using the Direct Test Mode app to better understand the requirements.
However, there is one aspect that remains unclear and not fully detailed in the documentation: the calculation of Packet Error Rate and how the RX synchronizes with the TX during the test.
How can i test the PER during the DTM mode 
What RX Tx synchronizes shouyld be 
 

[ketiljo]

Hi

You need two instances of DTM for this. Set one device as receiver and one as transmitter. Same datarate and channel for both. Packet type PRBS9 (TS only).

Press start test on the RX side. On the TX side, set the timeout to a few seconds. Press start test and wait for it to finish

When you stop the test on the RX side, it will report the number of packets it has received. You can adjust the timeout on the TX side untill you have for instance 1500 packets received. 

This is how the Bluetooth tested does as well. The DUT will just report  the number of packets it has received between test start and stop. The tester calculates the PER based on the number of sent and received packets. 

There's an old app note with some python script here: https://infocenter.nordicsemi.com/topic/struct_appnotes/struct/appnotes_nan34.html that you may be able to use with some tweaking.

Cheers,

Ketil