RE: (BLE or BT5) Measure latency between device (PI) and nrf52840

Marjeris Romero — Wed, 01 Apr 2020 11:25:45 GMT

Hi,

For BLE the minimum connection interval is specified by the Bluetooth Core Specification to be 7.5 ms, so for BLE the latency would be minimum 7.5 ms if you send one packet per connection interval. Please take a look at this old Devzone case for more information: https://devzone.nordicsemi.com/f/nordic-q-a/24013/minimum-connection-interval?ReplySortBy=CreatedDate&ReplySortOrder=Ascending

The radio in the nRF5 series chips can achieve much lower latency than 7.5ms, but you will need to use the radio in a propiertary protocol.

For your question about measurement latency, I think it will depend on how you define latency. I.e. are you measuring to/from application layer, transport-layer, PHY layer, etc.
When using timestamps you are also adding the time it takes to process the packet into the latency calculation, and the timestamps itself could also add some overhead to the calculation.
Another way to measure latency (on the PHY layer) will be to use a sniffer to track when the send and response packets are sent.

Best regards,

Marjeris