Power management of nRF52832 based custom board

[bojan]

Hello guys,

I have coin cell powered nRF52832 based sensor node. I develop the firmware in Segger Embedded Studio, SDK15.3.0.

On the pressure of a button on the sensor node board, I need to wake up and advertise BLE data. Once receiving advertising data, central device will establish BLE connection with my sensor node and will disconnect immediately (BLE_GAP_EVT_CONNECTED, BLE_GAP_EVT_DISCONNECTED events should be detected in my firmware with ble_evt_handler() function). I am doing this connect/disconnect action as a kind of handshaking protocol between advertising peripheral and central unit - to make sure my advertising peripheral was detected by central device because this is important to me.

Once disconnected from central device, I want my sensor node to enter deepest possible sleep mode and to be able to wake up only with external GPIO event (pressure of a button).

I imagine I should turn off SoftDevice before going to sleep mode and activate some low frequency oscillator. Once button is pressed, I should initialize SoftDevice (ble stack) and start advertising. Am I right about that?

What would be the most appropriate design example for me to start with? How to enable/disable BLE stack?

Thanks in advance for your time and effort!

Sincerely,

Bojan.

[Amanda Hsieh]

Hi, 

What would be the most appropriate design example for me to start with? How to enable/disable BLE stack?

You can refer to the Power Profiling Application which is implemented with the system off mode and enable/disable BLE stack.

-Amanda H.

[bojan]

Thanks, Amanda Hsieh!

I think putting the device into deepest sleep Power OFF mode and waking/resetting it with external button would be the way to go for me!

Once I implement that, will try to measure current consumption by the help of Power Profiler Kit.

I was reading somewhere on this forum that the set of the two following commands should help reduce power consumption even more:

sd_power_dcdc_mode_set(NRF_POWER_DCDC_ENABLE);
sd_ble_gap_tx_power_set(0);

I have external inductors on my board for DCDC:

What is your experience about those commands? Do I need to implement them before going to System OFF sleep mode?

Sincerely,

Bojan.

[Amanda Hsieh]

Hi Bojan, 

You could use the function sd_power_dcdc_mode_set() to enable the DCDC converter to have the lowest power consumption. See this post.

The SoftDevice function sd_ble_gap_tx_power_set() can set the TX power. Please see Radio current consumption (Transmitter). 

You can use them to reduce power consumption while an application running, but they are not necessary for the System off mode. Please see the System OFF mode.

-Amanda H.