nrf52 fails to transmit 20bytes data at 100Hz

[jpo38]

I'm using a PCA10040 V1.1.1 dev board (nrf52). I programmed it with "Nordic_HRM" example, but modified it to send 20bytes data at 100Hz.

Then, on my PC, I use a PCA10031 V1.1.0 dongle (nrf51) to retrieve the data. I simply compiled the nrf_heart_rate_collector example, linked with pc-ble-driver-2.0.0 driver. The dongle is programmed with connectivity_1.1.0_1m_with_s132_3.0.hex.

On some computer, nrf_heart_rate_collector reports ~100pkt/s, which is expected.

But on other computers, nrf_heart_rate_collector reports only between ~60pkt/s and 70pkt/s, some notifications are lost.

All computers are using the same dongle and the same version of the program, same pc-ble-driver and same SEEGER driver (which is 6.0.2601.5).

Any idea what could make 100Hz data transmission not work only on some specific computer? Note that I experienced data being lost with computers much faster than one with no data lost.

Ran sniffer with Wireshark as recommended, and I get very surprising results:

- When nrf_heart_rate_collector reported 64pkt/s, I can see more than 139 events "Rcvd Handle Value Notification" for a given second
- When nrf_heart_rate_collector reported 102pkt/s, I can see around 100 events "Rcvd Handle Value Notification" for a given second

100Hz_nrf_collector_64Hz.pcapng

100Hz_nrf_collector_102Hz.pcapng

EDIT: I tried to upgrade pc-ble-driver-2.0.0 to pc-ble-driver-2.2.1. Problem is still present. Don't know if it's worth trying to upgrade to 3.0.1

[jpo38]

Thanks for your help, we can try to swap, but it's hard to say how hard this will be. I checked and we use the latest SEGGER driver, so we can't expect a potential driver issue to be fixed.

[Kenneth]

Can you try to downgrade to an older SEGGER driver, such as 6.16c, and see if there is any difference:

https://www.segger.com/downloads/jlink/JLink_Windows_V616c.exe 

[jpo38]

Just tried that, but it also uses driver 6.0.2601.5. I even downgraded to the oldest version (5.00), it also uses driver 6.0.2601.5 and has the same issue...

[Kenneth]

I should mention that in addition to downgrade the driver, you also need to downgrade (roll-back) the firmware. This can be done by open "J-Link Configurator" and replace firmware.

[jpo38]

Hello Kenneth.

The problem is still present for us. Some time ago we tried to replace the dongle by a dev board but we never succeeded to make it work.

However, I worked again on this issue and could isolate something very wierd. Windows activity has apparently an impact on the actual data rate at which data can be retrieved. Please have a look at :

stackoverflow.com/.../using-a-qt-vista-style-widget-makes-my-ble-data-acquisition-faster-why

If this inspires you....