Round trip time measurement and coded PHY

[Elissa]

Hi, I want to measure Round Trip Time (RTT) varying data rate

However, when using coded phy, the RTT shows extremely long time

Using 1M or 2M with connection interval 30ms, RTT usually 26ms or 56ms, which is understandable, but using coded phy, it shows about 300~500ms

Is there any development issue about this? I saw that some codes of SDK said Coded PHY is just 'experimental'

I'm not sure this is because of explainable by bluetooth specification, or SDK development issue.

Thanks

[Susheel Nuguru]

I am not sure how you are measuring this and getting the info in RTT.

500ms is not correct, it cannot be that much. The max difference should be in micro seconds, not in milliseconds.

[Elissa]

Hi, thanks for reply.

I modified 'ble_app_att_mtu_throughput', so whenever test_run called, send a packet (just one packet) and measure the time from NRF_BLE_AMTS_EVT_TRANSFER_FINISHED event to NRF_BLE_AMT_C_EVT_RBC_READ_RSP event.

[Susheel Nuguru]

That is not the correct way to test as this includes all the software processing latencies to notify those events to the app. You should use RADIO notification API and check the time between the packet sent and packet received.