How to achieve the lowest power consumption on the Actinius Icarus (nrf9160) board?

[Nikil Rao]

Hi,

I'm trying to lower the power consumption om an Actinius Icarus board which uses an nrf9160 chip. I've been able to achieve a sleep current of 1.33mA and I'm not able to lower this any further. Could you please let me know what else I could do to lower the power consumption?

My setup - 

• Board - Actinius Icarus
• NRF Connect SDK - v1.2.0
• Modem FW - 1.1.1
• Sim - External NBIoT Sim card from 1nce which uses Deutsche Telekom band 8
• Antenna - Ethertronics penta 1002292
• Input - 4x1.5V batteries supplied to the Vin pin
• Current measurement - Multimeter inserted between batteries and Vin
• External peripherals - Using a 10k NTC with a 10k pullup voltage divider circuit connected to A1 for temperature measurement

Things done to reduce power consumption - 

1. Disabled logs in the project and SPM- 
   
   CONFIG_CONSOLE=n
   CONFIG_STDOUT_CONSOLE=n
   CONFIG_LOG=n
   CONFIG_SERIAL=n
   CONFIG_UART_CONSOLE=n


2. Enabled power management - 
   
   CONFIG_SYS_POWER_MANAGEMENT=y
   CONFIG_DEVICE_POWER_MANAGEMENT=y


3. Enabled PSM with these parameters (Also with different p-tau like 10 min, 1 hour, etc) 
   
   CONFIG_LTE_PSM_REQ_RPTAU="11000001"
   CONFIG_LTE_PSM_REQ_RAT="00000001"


4. Removed bootloader - 
   CONFIG_BOOTLOADER_MCUBOOT=n
   
   

The current drawn through the NTC voltage divider is around .16mA. I have connected to the AWS server via MQTT and send sensor data to the server at a fixed interval. I send the data and go to sleep for a defined time and repeat the process. I observe a constant sleep current of 1.3mA. When the device wakes up and sends data, I see spikes of 50mA and it comes back to 1.3mA after 2 seconds according to CONFIG_LTE_PSM_REQ_RAT.

For testing, I also edited the same project and made the device run an infinite while loop with a sleep function and still see that the sleep current is 1.3mA. From what I understand it looks like the modem does go to PSM (if I disable it I see a sleep current which keeps fluctuating between 1.3mA to 50mA). The sleep current with the modem switched off (with an AT+CFUN=0) command also shows me a sleep current of 1.3mA. This leads me to believe that there are some other peripherals which are switched on and consuming power. I'm not able to figure what else I should be doing at this point to lower the current consumption. Could you please advise me on  how to proceed? Thanks a lot!

Nikil

[Håkon Alseth]

Hi,

 

Could you try to disable everything related to UART, specifically the at_host?

CONFIG_UART_INTERRUPT_DRIVEN=n
CONFIG_AT_HOST_LIBRARY=n

 

This one will setup a uart directly, but I'm a bit surprised that you get your current configuration to compile, as at_host would have a dependency on SERIAL being enabled.

 

PS: It might take around 1 minute before you have successfully entered sleep after entering PSM, as there is a RRC idle period (individually set by the network), in which could explain the fluctuation you have previously seen. If you still get ~1 mA even after the modem is disabled, then its still something in the application that causes this.

 

Kind regards,

Håkon

[Nikil Rao]

Hi,

Sorry I keep enabling and disabling logs for testing and I forgot to disable those two configs. It doesn't compile without disabling them, true. I have CONFIG_UART_INTERRUPT_DRIVEN=n and  CONFIG_AT_HOST_LIBRARY=n disabled and I still see ~1 mA.

"It might take around 1 minute before you have successfully entered sleep after entering PSM". Yes, I have seen this in action by enabling and disabling PSM. When PSM is enabled, I see spikes in current for about a minute before it settles around ~1 mA while it does not settle when PSM is disabled.

[Håkon Alseth]

Hi,

 

Could you try zephyr/samples/basic/blinky, with CONFIG_SERIAL=n & project configured with the secure region, and see if this goes below 1 mA?

Can it be that one of your LEDs is lit up? On the nRF9160-DK, LEDs are buffered, but I'm not sure how they're connected on this board (couldn't find a schematic)

 

Kind regards,

Håkon