Understanding connection interval, nRF Sniffer and transfer speed

RE: Understanding connection interval, nRF Sniffer and transfer speed

Stian Røed Hafskjold — Thu, 16 May 2019 11:34:48 GMT

Are you requesting data to be sent every time you send a notification? If so, it will require two connection events. An then you will always get two empty packets because of how the RX/TX pair work.

RE: Understanding connection interval, nRF Sniffer and transfer speed

Burgers — Mon, 13 May 2019 11:54:54 GMT

Hey Stian, thanks!

I checked my code, and I'm using notifications,

hvx_param.type      = BLE_GATT_HVX_NOTIFICATION
hvx_param.p_data    = value;

where value is my buffer (486 bytes), and,

sd_ble_gatts_hvx(pressure_service->conn_handle, &hvx_param)

I don't know why I get the empty packets.

RE: Understanding connection interval, nRF Sniffer and transfer speed

Stian Røed Hafskjold — Mon, 13 May 2019 11:24:28 GMT

So one connection interval consists of a RX and TX pair. Seen from the slave, the radio is receiving the request, then switches over to TX immediately. It has not processed the request yet, so sends an empty packet. Then the next connection interval the slave receives an empty packet from the master, and then sends the payload when switching over to TX. So yes doing it this way it requires two connection intervals to send the payload. However, when using notifications you do not have to wait for a request to send data. You just put all the data you want to send in the TX buffer and the slave will burst out the data every TX event.