NRF5340 Max throughput

[Branislav]

Hello,

I have a nrf5340dk communicating with nrf52840 dongle connected to a pc with UART baud rate of 2M.

Connection parameters are:

• 7.5ms Conn interval
• 1ms Slave latency
• 247 MTU
• 251 DLE
• 2M PHY

nrf5340dk is configured as nus peripheral.

In the code, there is a high priority thread that is in an infinite loop calling bt_nus_send with a 244 byte buffer and here are the results I get when profiling the packets:


Although, in here it suggest I should be getting a ~1.3 Mbps throughput with 400 ms connection interval, but instead I get this:


I wanted to ask, is there something that needs to be additionally done to get the ~1.3 Mbps throughput or is this the limitation of the hardware, and if someone knows why I get less throughput when I set connection interval to 400 ms.

Additional info:

• NRF Connect SDK: v1.8.0 and v1.9.1 were used, there was no difference between them
• PC is running Windows 10, communicating via Blatann library
• nrf5340's antenna is a few centimeters away from nrf52840 usb dongle

[Branislav]

Thank you, that was the reason why the throughput was so slow with 400ms connection interval, this is the result I get after changing the event length:

There are some weird packet issues for the first 20 seconds of the stream tho.

I only want to circle back to my previous question, would it be possible to achieve 1.3 Mb/s throughput with the nrf52840 dongle or is this the limit of the hardware/default firmware?

[Vidar Berg]

Glad to hear that it worked.

I have not been able to reach 1.3 Mb/s with the pc-ble-driver, and I think it's a combination of overhead of having the serialized softdevice communication and latency introduced by the USB transport. Scheduling of USB events on the PC may be delayed by other OS tasks.