Lowest latency on nRF52840

[Tomaszc]

Hello,

I want to build a wireless mouse with the highest possible refresh rate. I'm considering using an nRF52840 dongle. How often can packets be sent from one nRF52840 to another? I see that bluetooth low latency allows for a 1ms delay. Using 2.4, can packets be sent more frequently? If so, what is the limit? Can I speed this up using a different chip?

[Kenneth]

Hello,

If you want interoperability with other vendors Bluetooth Low Energy (BLE) is the way to go, normally shortest is 7.5ms.

If it's Nordic BLE in both ends, then it can support LLPM mode, which reduce it to 1ms. You can read more about it here:
https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/samples/bluetooth/llpm/README.html 

If it's Nordic proprietary in both ends, then you can use ESB, which will reduce it further (likely in the 250us range with no packet loss):
https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/protocols/esb/index.html 

It's theoretically possible to go even lower by working directly on the hardware, but the closer you work to the hardware, the more likely the development time will increase, since you need to solve security, pairing, quality of service etc.

Kenneth

[PaKa]

For Bluetooth look at SCI, Short Connection Intervals. Came with the November update of the Bluetooth spec and allows for shorter CI than 1ms. Some support in the main branch of nRF Connect SDK today.