2 protocols (Proprietary protocol & BLE) on nRF51822

[Victor Wong]

We are working on a asset tracking device which will operate with a 3V CR2016 (85mAh) coin cell battery or smaller.

Per our understanding, the max interval of S110 softdevice for BLE is 4 seconds. However, our device will need to keep in storage for 6 months and able to operate for 1 month at least.

In order to achieve 7 months battery life, we are thinking to implement 2 software stacks (Proprietary RF and BLE) on nRF51822 as understand nRF51822 is capable of concurrently supporting both Bluetooth low energy and proprietary RF software protocols. By default, the device is running on Proprietary RF and advertise every 500 seconds. Until the device receives an “wake-up” message and it will switch to BLE protocol and advertise at every 2 seconds.

Please kindly advise us if above is doable? If no, what will be your recommendation?

[Stefan Birnir Sverrisson]

Hi

It is doable to implement application that runs both BLE and propriatery protocol. There is one such application in the SDK, that runs BLE and Gazell. The example is located at \Nordic\nrf51822_v6_1_0\Board\nrf6310\s110\ble_app_gzll. Gazell is Nordic's propriatery wireless protocol. It runs BLE, and with a push of a button, BLE stack is disabled and Gazell is enabled. Push the button again and Gazell is disabled and BLE is enabled.

It is also possible to run propriatery protocol and BLE concurrently, then you will have to utilize timeslots API, described in the S110 SDS document. With the Timeslots API, the application can request the S110 stack (softdevice) for timeslots in between BLE radio events, where the proprietary protocol can be executed. A simple Timeslot API example is attached that was tested with nRF51 SDK v6.0.0 and S110 v7.0.0.

ble_app_hrs_with_timeslot.zip

Anyway, if your requirement is to have 18mAh battery last for 7 months, it might be possible with just BLE advertising. You are correct that the maximum connection interval is 4 seconds, but from your description, suspect you want to advertise only, am I correct? The advertising interval can be up to 10.24 seconds. With a BLE advertising interval of 10.24 seconds the nRF51 consumes around 6uA, which gives you estimated lifetime of 19.6 months. If you let the device advertise with 2 second advertising interval, the current consumption is ~15-18 uA, wich will give you lifetime of about 7 months.