With very low data rates and short packets between two nRF52840s which of the following can operate at the lowest power?

[Marty]

With very low data rates and short packets between two nRF52840s which of the following can operate at the lowest power?

1) ble peripheral to ble central uart

2) Enhanced ShockBurst (ESB) - basic protocol supporting two-way data packet communication

3) IEEE 802.15.4

4) Gazell

Thank you!

[Edvin]

Hello,

I would recommend BLE. The reason for this is that BLE is engineered with current consumption in mind. Short radio times and a protocol that ensures you don't loose packets.

You could save some air time using ESB, but you would need to write your own protocol, similar to BLE ensuring that the receiver is using the radio in RX mode when the transmitter is transmitting. Probably not worth the effort.

IEEE no. always in radio RX

Gazell. Not sure how it compares, but probably not better than BLE.

The thing here is that scanning and transmitting using the radio on the nRFs consume roughly the same amount of current. Therefore you would want the devices to know exactly when the other device is going to transmit, and turn on the radio only at that point in time. This is basically the ground principle in BLE. The reason I mentioned ESB is that there are some header bytes in a BLE packet that you could save, but I don't think it is even worth looking into, because there would be a lot of work to implement the power saving that you have on BLE.

So if you decide to go with BLE, I would recommend setting as high connection interval as possible, and use the maximum slave latency. Slave latency means that a peripheral can skip n connection events (the event that occurs every connection interval) if it doesn't have anything useful to say. This is commonly used in e.g. HID devices, which from an embedded point of view, mostly does nothing but wait. Whenever a keyboard key or mouse button is pressed, it will report this, and go back to waiting, skipping n connection intervals unless another action has occured.

Best regards,

Edvin

[Marty]

Thank you for your quick reply Edvin.  I have a few products in the market now using 802.15.4 radios and a proprietary point to point protocol.  How do you think that would stack up against a BLE solution for power consumption?

Thank you again!

[Edvin]

That depends entirely on the proprietary protocol, but as I mentioned, BLE is engineered for low power consumption, so if any, it is probably not much better than BLE. In fact, my suspicion is that BLE is more power efficient than a proprietary 802.15.4 protocol.

Best regards,

Edvin

[Marty]

Edvin,  I really appreciate your insights. Thank you!