High current when using BLE NUS

[rmakl]

Hi,

I am starting to finalize a development stage and was looking at the current consumption of my device. I noticed, that when something connects to it and is starting to use the NUS service, current consumption skyrockets to 7mA and stays there, even after disconnecting every BLE connection.
This happens either:

• I connect using Norduc UART Android App
• I connect using nRF connect, then click on the TX Characteristic notification enable
• I connect using a custom Android App that uses BLE NUS
• Right after I make connection with the device (non-NUS) and my m_conn_handle becomes valid and I try to send data with ble_nus_data_send();

Here is an extract of an RTT log:

 0> <info> pwr_mgmt: CPU Usage: 0%
 0> <info> pwr_mgmt: CPU Usage: 0%
 0> <info> pwr_mgmt: CPU Usage: 0%
 0> <info> pwr_mgmt: CPU Usage: 0%
 0> <info> pwr_mgmt: CPU Usage: 0%
 0> <info> pwr_mgmt: CPU Usage: 0%
 0> <info> pwr_mgmt: CPU Usage: 0%
 0> <info> pwr_mgmt: CPU Usage: 0%
 0> <info> pwr_mgmt: CPU Usage: 0%
 0> <info> pwr_mgmt: CPU Usage: 0%
 0> <info> pwr_mgmt: CPU Usage: 0%
 0> <info> pwr_mgmt: CPU Usage: 0%
 0> <info> pwr_mgmt: CPU Usage: 0%
 0> <info> pwr_mgmt: CPU Usage: 0%
 0> <info> pwr_mgmt: CPU Usage: 0%
 0> <info> pwr_mgmt: CPU Usage: 0%
 0> <info> pwr_mgmt: CPU Usage: 0%
 0> <info> pwr_mgmt: CPU Usage: 0%
 0> <info> pwr_mgmt: CPU Usage: 0%
 0> <debug> nrf_ble_gatt: Requesting to update ATT MTU to 158 bytes on connection 0x0.
 0> <debug> nrf_ble_gatt: ATT MTU updated to 158 bytes on connection 0x0 (response).
 0> <info> pwr_mgmt: CPU Usage: 0%
 0> <debug> nrf_ble_gatt: Peer on connection 0x0 requested a data length of 123 bytes.
 0> <debug> nrf_ble_gatt: Updating data length to 27 on connection 0x0.
 0> <debug> nrf_ble_gatt: Data length updated to 27 on connection 0x0.
 0> <debug> nrf_ble_gatt: max_rx_octets: 27
 0> <debug> nrf_ble_gatt: max_tx_octets: 27
 0> <debug> nrf_ble_gatt: max_rx_time: 1096
 0> <debug> nrf_ble_gatt: max_tx_time: 1096
 0> <info> app: BLE NUS connected
 0> <info> pwr_mgmt: CPU Usage: 4%
 0> <info> pwr_mgmt: CPU Usage: 38%
 0> <info> pwr_mgmt: CPU Usage: 39%
 0> <info> pwr_mgmt: CPU Usage: 38%
 0> <info> pwr_mgmt: CPU Usage: 38%
 0> <info> pwr_mgmt: CPU Usage: 38%
 0> <info> pwr_mgmt: CPU Usage: 38%
 0> <info> pwr_mgmt: CPU Usage: 38%
 0> <info> pwr_mgmt: CPU Usage: 38%
 0> <info> pwr_mgmt: CPU Usage: 38%
 0> <info> pwr_mgmt: CPU Usage: 38%
 0> <info> pwr_mgmt: CPU Usage: 38%

As you can see, CPU load is increased after NUS activity, but no other tasks are carried at that time.

What seems to be the problem?

I'm using:

• s140_nrf52_7.0.1_softdevice.hex
• nRF5_SDK_for_Thread_and_Zigbee_v4.1.0_32ce5f8

Best Regards,

Roland

[Vojislav]

As I know you need to disable UART and disconnect the programmer so you get the real power consumption for the NUS example

[rmakl]

Hi Vojislav,

I forgot to mention, that I'm not using UART, or any other peripheral. I would like to use NUS for raw data transfer. As for the programmer, I measure the elevated consumption after a power reset, so the nRF is not in debugger mode. Also, the project is compiled in 'Release' config and has no other problem whatsoever.

BR,

Roland

[Vojislav]

I understand. I do not know your hardware configuration so just be aware that having programmer pins connected can cause an increase in power consumption. 
Are you using NCS or nRF5SDK?
Also, RTT is adding to power consumption, so turning that off as well will help. 

[rmakl]

RTT might add some cosumption, but when I'm not using NUS, my IDLE current can go <10uA, so the 7mA increase is nothing related to that.
I'm using a custom hardware, but then again, without NUS, I have no problem with consumption, BLE generally. I'm even using DFU and other services, all of them works fine (even those, which have NOTIFY attributes). Only the NUS is giving me trouble, so this purely a software issue.

[Vojislav]

Yes, I agree, hope that Nordic can help. Good luck