simple example for measuring power consumption

[bios-bob]

i'm looking for a simple example which i can run on nRF9151 DK (v0.9.0) where i can profile power consumption....

ideally, the example would repeatedly send packets over a cellular content -- and then enter a "low-power" sleep mode in between....

is the nrf/samples/cellular/udp application my best choice here???

if so, what current consumption numbers might i expect to see (using my PPK) -- as a sanity check for me....

[bios]bob

PS -- the AI answer gives me a place to start....  my let's keep this ticket open in case i have a follow-up question.... 

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Recommended Sample

The Cellular: UDP sample (samples/cellular/udp) in the nRF Connect SDK is the best choice for power profiling on the nRF9151 DK [Cellular: UDP Overview].

Key benefits of this sample for power measurements:

• Transmits simple UDP packets to a server at configurable intervals [Cellular: UDP Overview].
• Requests low-power network parameters, including Power Saving Mode (PSM) and eDRX [Cellular: UDP Overview].
• Logging output is disabled by default to minimize baseline current consumption [Cellular: UDP Overview].

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Expected Current Consumption Benchmarks (PPK Sanity Check)

Note: Power consumption numbers vary depending on network conditions, signal quality, and network timers (such as RRC inactivity timers). [Power consumption]

1. PSM Floor (Low-Power Sleep):

   • ~2.7 µA to ~4 µA: Baseline current when the device enters PSM between transmissions [Real-time power measurement; YouTube: How to Power Profile].
   • During this mode, internal DC/DC converter charging cycles cause brief mA spikes, but quiet periods drop below 1 µA [Power consumption].
   • Troubleshooting: If you measure ~400 µA to 700 µA at idle, ensure that logging/UART is fully disabled [YouTube: How to measure power].
2. Active Transmission Event:

   • Peak Current: Spikes up to ~300 mA to 400 mA during maximum RF output bursts [Real-time power measurement; Power consumption].
   • Event Charge: A typical data upload sequence (including network setup, transmission, and RRC inactivity time) consumes around ~115 mC to 117 mC over ~12 seconds [Real-time power measurement; Real-time power measurement].
3. Average Current Over Time:

   • ~1.0 mA to 2.3 mA: When transmitting frequently (every 30 to 40 seconds) [Testing RAI feature; YouTube: How to measure power].
   • < 100 µA (e.g., ~80 µA to 90 µA): When transmitting infrequently (every 15 to 20 minutes), as the device remains in PSM sleep for most of the duration [YouTube: How to Power Profile].

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Helpful References

• Cellular: UDP Sample Documentation [Cellular: UDP Overview]
• Power Profiling Cellular Applications Guide [Real-time power measurement]
• nRF9151 Hardware Verification Guidelines: Power Consumption [Power consumption]
• Online Power Profiler for LTE [Power Class 3 modem current consumption]

[Tomas M]

Hi Bob,

Definitely start out with the resources the AI recommended if you find them helpful. I wanted to just add on that we have a course on developing low-power applications on DevAcademy here. Now, it's not entirely applicable to your use-case since it targets BLE applications specifically, but the majority of concepts transfer over directly. Especially check out Lesson 3 for information on profiling. It's especially easy if you have one of our Power Profiler Kits (PPK).

Let me know if you have any questions!

Best regards,
Tomas

[bios-bob]

hi tomas,

the UDP example is working fine for me, with idle current in the ~2uA range....

i'm bringing up my own "bare-metal" environment on the nrf91 M33 core -- similar to what i already have on the nrf52 and nrf54....

everything is working functionality -- though my idle current is over 4mA !!!

here's a simple standalone program that illustrates my startup sequence before WFI....

#include <stdint.h>
#include "nrf9120.h"

int main(void)
{
    /* Ensure modem domain is off */
    NRF_POWER_S->LTEMODEM.FORCEOFF = 1;
    while (NRF_POWER_S->POWERSTATUS != 0) {
    }

    /* Select low-power / variable-latency mode */
    NRF_POWER_S->TASKS_LOWPWR = 1;

    /* Start 32.768 kHz crystal */
    NRF_CLOCK_S->EVENTS_LFCLKSTARTED = 0;
    NRF_CLOCK_S->LFCLKSRC = CLOCK_LFCLKSRC_SRC_LFXO;
    NRF_CLOCK_S->TASKS_LFCLKSTART = 1;

    while (NRF_CLOCK_S->EVENTS_LFCLKSTARTED == 0) {
    }

    NRF_CLOCK_S->EVENTS_LFCLKSTARTED = 0;

    /* Release any explicit HFXO request */
    NRF_CLOCK_S->TASKS_HFCLKSTOP = 1;

    /* Sleep forever */
    while (1) {
        __asm volatile ("wfi");
    }
}

i've verified that the WFI does *not* return....

presumably, i've left "something running" that's consuming the 4mA....  again, this is directly out of reset.... (no zephyr!!!!)

[bios]bob

[Tomas M]

Hi Bob,

Thank you for your patience with this topic. Can you tell me about the bare-metal environment for the nRF9151? As far as I'm aware, the nRF Connect SDK bare-metal is for the nRF54L series devices.

Best,
Tomas

[bios-bob]

hi tomas,

by "bare-metal", i mean *NO* SDK....  as i've done with other nordic devices, i have my own (very, very small) runtime environment which i'm currently porting to the nrf91....

i've actually gotten a little further -- now having ported the core environment to the nrf91....

my original question came from my first power measurements -- which showed a 4mA sleep current!!!!

in the meanwhile, i've kept investigating the protocol between the M33 and the MODEM....  at this point, i understand enough to perform the initial "handshake"....  my goal is to essentially reproduce the zephyr UDP example -- but in just a fraction of the code!!!!

in the very near-term, i'm using the tfm_s.hex image as a "bootloader" for my own (very small) app....  for reasons i'm still trying to understand, this image is putting the M33 into some NS state that is *necessary* to communicate with the MODEM....

so, at this time i'm not "blocked" -- though always looking to better understand the "bare-metal" interaction between M33 and MODEM...

[bios]bob