nRF52840 BLE OTA test use CMW500's connect mode

[RongLinQin]

Hi nordic support:

      Our product used nRF52840, we tried test nRF52840's BLE OTA RF performance with CMW500. After the nRF52840 device is assembled with the casing, it is inconvenient to route a serial cable for Bluetooth OTA testing via nordic's DTM (Direct Test Mode) mode. Therefore, we attempt to perform the OTA testing in the BLE connection mode of the CMW500.

      Our Bluetooth application is modified based on the NUS sample program "ble_app_uart" from the nrf5_sdk_17.1.0_ddde560. During the testing process, the CMW500 first searches and connects to the nRF52840, then gradually reduces the TX (Transmit) power. When the TX power drops below -85 dB, the BER (Bit Error Rate) becomes a non-zero value, and the BLE connection is subsequently disconnected abnormally. Following picture "nRF52840_OTA_test.jpg" shows the test log. This issue causes repeated reconnections during the OTA testing process, and the total OTA testing time increases severalfold.

       

      

    We compared another ble device（a ble door locker） which used other manufacture's BLE chip, and its testing can be carried out normally without any disconnections during the entire test process. We captured the BLE sniff logs of both during the testing process.

     Could you help us analyze this issue and  guide us how to modify the nRF SDK code to avoid disconnections during OTA testing with the CMW500? And this modification is only for testing purposes and will not be applied to the official products.

      Thanks!

     

3058.sniff_nRF52840_CMW500.7z6281.other_ble_device_test_ok.7z

BRs

Qin, Rong-Lin

[JONATHAN LL]

Hi Qin, 

Have you had the product reviewed? Could there be some mismatch on the antenna or the RF matching making the device preform worse than expected? 

Regards,
Jonathan

[RongLinQin]

Hi Jonathan:

    Thanks for your support. 

    Our product has already mass production, and all RF performance have passed testing. We also tried nordic  development kit PCA10040, The phenomenon remains the same.

BRs

Qin, Rong-Lin

[JONATHAN LL]

the CMW500 first searches and connects to the nRF52840, then gradually reduces the TX (Transmit) power. When the TX power drops below -85 dB, the BER (Bit Error Rate) becomes a non-zero value

If you continue to drop the TX-power , it will at some point lead to a disconnect.  So this would be expected behavior.

 This issue causes repeated reconnections during the OTA testing process, and the total OTA testing time increases severalfold.

If you don't want to reconnect - then either (1) Don't automatically re-start advertising after a disconnect , or (2) Don't automatically scan&connect to the peripheral after a disconnect.


Regards,
Jonathan