Packet number in one connection interval with 2M phy

[helen]

Hi Nordic，

One of my customer has a problem about 2M phy.

They use 52840 connected with IOS via 2M phy.

They set MIN_CONN_INTERVAL and MAX_CONN_INTERVAL both to 20, which mean 25ms connection interval.

The ATT MTU is 247.

When they set NRF_SDH_BLE_GAP_EVENT_LENGTH to 6(7.5ms), they found there is only on packet in one connection interval.

When they set NRF_SDH_BLE_GAP_EVENT_LENGTH to 20, they found there is only 5 packets in one connection interval.

in theory, transmit one packet of 251 bytes need less than 2ms by 2M phy.

for gap event and connection interval 25ms, there should be 12 packets in one interval, but there is only 5.

What am I lost when calculate it?

thanks.

[Simonr]

Hi

Sorry, I thought they had issues with the MTU sizes on iOS. As long as packets are queued in the SoftDevice when the connection event starts, the SoftDevice will try to send as many packets as uit can in a given connection interval, as long as the time set aside for the connection on each connection interval isn't exceeded. It's also a possibility to enable extended BLE connection events.

Also, is there a reason they should get 12 packets instead of 5 in the 25ms? I'm struggling to see the math here.

Best regards,

Simon