RE: Bluetooth Bandwidth limitations

Sigurd — Tue, 20 Aug 2024 10:53:58 GMT

Hi!

[quote user=""]1. The total amount of data which can be sent by a slave in one second is 1 / bluetooth connection interval * 20 bytes. So for BT con interval of 200ms its 100 bytes.[/quote]

No, most devices can send several packets per connection interval. Also, if both sides of the BLE link support longer ATT MTU, then you can also increase the payload , and are not limited to 20 bytes either.

[quote user=""]2. The total amount of data which can be sent to a slave is about 3 to 4 times above.[/quote]

No. It depends on ATT_MTU, DLE, connection interval, how many packets per connection interval, etc.

[quote user=""]3. I've partially tested this arrangement (not as a UART but by connecting to nRFConnect). The smaller the connection interval, the more 802.15.4 packets are lost. This is to be expected as the radio is being multiplexed and BT take priority.[/quote]

Correct.

[quote user=""]4. If the slave is sending 40 bytes, is the packet split in two and sent over 2 connection intervals? Is it possible to increase the 20 byte limit?[/quote]

It depends on the devices you are using and how they are configured. If you are using e.g. nRF52 on both sides of the link, then yes, there is no problem to increase the payload and send multiple packets per connection interval.

[quote user=""]5. Is it possible for the slave to predict when the softdevice will take control of the radio? In this way it can schedule complete 802.15.4 transactions between BT connections.[/quote]

This happens under the hood if are using e.g. Thread, see e.g. this link: https://infocenter.nordicsemi.com/topic/sdk_tz_v4.2.0/ble_154_multiprotocol.html?cp=9_3_4_0_1#ble_154_multiprotocol_dynamic

[quote user=""]We are using the NRF5 thread and zigbee protocol (only one which supports multiplexing).[/quote]

If you are starting a new project, I would recommend using our newer nRF Connect SDK instead.

https://www.nordicsemi.com/Products/Development-software/nRF-Connect-SDK

https://www.nordicsemi.com/Products/Development-software/nRF-Connect-SDK/GetStarted?lang=en#infotabs

RE: Bluetooth Bandwidth limitations

Liam — Mon, 19 Aug 2024 10:29:59 GMT

Hi,

Is there any update on this please?

Liam