Advertizing in low power mode

RE: Advertizing in low power mode

Xav — Mon, 06 May 2019 13:11:54 GMT

The uart module has high current consumption when it is active.

I need to stop the module to reduce consumption during advertising (app_uart_close()).

RE: Advertizing in low power mode

Xav — Mon, 06 May 2019 09:38:17 GMT

Hi Joseph,

Effectively, i have reversed the values. Sorry.

I think that the uart module have a greater consumption. When I insert the uart module in "ble_app_hrs", the consumption is identical to "ble_app_uart".

RE: Advertizing in low power mode

Joseph Ayuk — Mon, 06 May 2019 09:28:22 GMT

Hi Xav,

First I think you have reversed the values. The advertising interval is the time between each advertising event and the advertising timeout is used to tell the device for how long it should advertising. so if I can arrange the values, this is what we get:

For "ble_app_uart":

-advertising interval = 40ms

-advertising timeout = 180 seconds

For "ble_app_hrs":

-advertising interval = 187,5ms

-advertising timeout = 180 seconds

OK from the value of the constants that you gave, it is clear that the "ble_app_hrs" uses less current than the "ble_app_uart". This is because the advertising interval for ble_app_hrs" is greater than that of "ble_app_uart". With an advertising interval of 180 seconds for both cases,

-"ble_app_hrs" sends a total of 180/0.1875 = 960 advertising packets to the peer

-"ble_app_uart" sends a total of 4500 advertising packets to the peer

You can begin to see why the current consumption of one is greater than the other right?. Now if you want to reduce this, you can reduce your advertising timeout and increase your advertising interval.

RE: Advertizing in low power mode

Xav — Mon, 06 May 2019 06:22:00 GMT

Hi Joseph,

For "ble_app_uart" :

- advertising timeout = 40ms

- advertising interval = 180 seconds

- mode of advertising : ble_adv_fast_enabled = true

For "ble_app_hrs" :

- advertising timeout = 187,5ms

- advertising interval = 180 seconds

- mode of advertising : ble_adv_fast_enabled = true

It is the default values of examples give by Nordic.

RE: Advertizing in low power mode

Joseph Ayuk — Fri, 03 May 2019 12:43:29 GMT

Hi Xav,

Can you give me the advertising timeout and the advertising interval of each of the examples (ble_app_hrs and ble_app_uart) ? In order to answer your question, I will need to know the values of these constants. Also give the modes of advertsing used by each example (fast mode, slow, directed etc...)

RE: Advertizing in low power mode

Xav — Fri, 03 May 2019 10:19:28 GMT

Hi,

I tried with PCA10040 different measurements. With "ble_app_hrs" example, and "ble_app_uart" example. I measure the current consumption of the board after cutting SB9 connection.

With "ble_app_hrs", there is advertizing with a low current of 3µA with a peak during advertisement.

With "ble_app_uart", there is advertizing with a low current of 2mA with a peak during advertisement.

What is the difference between both applications for the low current ?

Regards,

Xavier

RE: Advertizing in low power mode

Joseph Ayuk — Mon, 15 Apr 2019 08:31:25 GMT

Xav first you need to understand that it will be impossible to be in low power mode if you have to do a continuous advertisement. How ever, you can minimize the current consumption by reducing the advertising timeout and increasing the advertising interval just as thcooke77 said. Now if you want to advertise at all times, I suggest you start advertising again as soon as your advertising timeout expires and your nrf51 enters the IDLE MODE. You can also use an app_timer to trigger the advertising after a certain period still when you enter the IDLE MODE. I can help you if you share your code on what you have done.

Regards

Joseph Ayuk

RE: Advertizing in low power mode

Kenneth — Thu, 28 Mar 2019 14:35:05 GMT

Take a look at this:

https://devzone.nordicsemi.com/b/blog/posts/optimizing-power-on-nrf52-designs (in general the same applies to nRF51, but the nRF52 will ensure lower power)

RE: Advertizing in low power mode

Xav — Thu, 28 Mar 2019 07:53:04 GMT

Hi,

My product is designed with the nRF51. I want advertise all times. Or if possible advertise and switch to low power mode (no system off), and wakeup and advertise again, and so on.

Regards.

RE: Advertizing in low power mode

thcooke77 — Wed, 27 Mar 2019 16:25:56 GMT

Xavier, a couple of questions:

Do you absolutely need to use an nRF51? The nRF52 uses much less power in standby and system off.

Will you be using a timer to wake up and advertise or just advertise at all times?

To specifically address your question with the information you have provided, the nRF basically does its own power management. So if it's not doing anything, it places itself in standby, which is the lowest power mode with RAM retention. If you need to completely shut down the chip, then calling

sd_power_system_off(); //if softdevice is enabled

NRF_POWER->SYSTEMOFF = 1; //if softdevice is not enabled

will place it in the lowest power mode available however it can only be woken up from this state by setting by a GPIO, reset pin state change or power reset.

For lowering power while advertising, you will need to adjust advertising timeout and interval to see what works best for your application. Shorter time == less power and longer interval == less power.