NRF52 Sleep Mode and BLE Advertising MBED

[OsmanKameric]

Hi all,

first of all I'm new to NRF and BLE applications so I'm truly sorry if some of my questions are very basic and if answer to some of them is already posted somewhere. I probably should have done more research.

Questions:

1. Is it possible for NRF52 to enter sleep mode but continue BLE advertising? If it's possible is there a MBED project example that enables the user to wake up the NRF when connecting to BLE on NRF and when disconnected NRF restarts advertisement and goes to sleep again?

1a. I read that NRF52 supports 2 type of sleep modes. One can be interrupted by any event and the other with GPIO. I found couple of simple examples that set sleep mode ON and OFF and when measuring nRF current consumption I get around 13µA for one mode and around 0.2µA for second mode. Is it possible to get similar consumption when in sleep mode but advertisement is active (cca 10-100µA)

Thanks

[Jørgen Holmefjord]

Hi,

I would recommend that you have a look at this post about BLE on the mbed platform. It describes the ble.waitForEvent() function that will put the device into low power mode between BLE events. You should also be able to use this chen you are in a connection.

I'm not sure about how much control you have of the power consumption when using the mbed platform, but according to this post, the BLE_Beacon example consumes ~35µA. Using our SDK, you can expect to achive the current consumption shown by the nRF52 online power profiler.

The two possible sleep modes in the nRF52832 is called system on and system off mode. System on mode is the one used when the chips is advertising or in a BLE connection. System off is used for longer sleep periods, and can only be waked by reset, GPIO, NFC field or LPCOMP events. Wakeup from system off mode will trigger a reset of the chip. You can find some examples of sleep modes on our GitHub page.

Best regards,

Jørgen

[OsmanKameric]

Hi Jørgen,

thanks for helping me out with my issue. It seems that ble.waitForEvent() function enables low power mode. I was looking at examples on this repository mbed-os-example-ble which contains BLE example applications for mbed OS 5.0 and none enter low power mode in any case. But examples from mbed compiler that are for mbed OS 2.0 use ble.waitForEvent() to enter sleep mode and reduce current consumption. I have to do more research to see why OS 5.0 applications won't enter sleep mode in examples. Thanks again Osman

[Tamás]

Hi Osman, just wondering if you reached any conclusion regarding this issue? I need to enable low power mode in an app that was written following the OS 5.0 examples and not sure what the best way is to mix ble.waitForEvent() and eventQueue.dispatch_forever().

[Yogesh]

I am currently facing the same issue with the NRF52832, where the system on sleep mode, is still consuming a lot of power and this is because of an existing issue in the mbed os5 platform, which prevents the NRF52 from sleeping for more than a few ms. Here is a Link to the issue that I am tracking at the mbed site.

Thanks, Yogesh