send 2 samples (12 bytes each) every 2ms in nrf52DK

[Nivetha]

Hi! I'm using nrf52 DK as central and nrf52dk as a peripheral device. Connection interval 10ms. I want to send 10 samples each of 12 bytes every 10ms connection interval. But is it possible to push 2 samples every 2ms? Or is it that I need to wait for 10ms to receive all the 10 samples? It is a medical device and we need to meet real time requirement. Each ADC will send 1 sample and 2 samples have to be sent every 2ms. Is it possible to achieve this throughput?

Connection Interval 10ms Softdevice s140 central nrf52DK peripheral nrf52DK

I am aware of the fact 7.5ms is the minimum connection interval. But in nRF52 Series > SoftDevices > S132 SoftDevice > S132 SoftDevice Specification >Bluetooth low energy data throughput.. There is a case with event length 2.5 ms. Is that connection interval?

[run_ar]

The event lenght is not the connection interval. It is used by the scheduler; The time set aside for this connection on every connection interval in 1.25 ms units.

So I'm afraid you have to buffer the samples and send them all in the first available connection event. Just make sure you have enough buffer space: hvn_tx_queue_size. Note that it might make sense to groupe the samples and send longer att mtu's.

[Nivetha]

Okay. Got it. Thanks! My packet size is 48 bytes. I can wrap all the 10 samples within 48 bytes. So, the att_mtu size should be 48 + 3bytes for over head, is it? Or we should only set 23, 158, 247?

[run_ar]

Use the length you want :) In addition you could look at Data Length Extension, although it's not really needed in your case.