Power Consumption Anomalies in NB-IoT Devices Quectel BC660K-GL with Custom LwM2M Server based on Leshan Server ,while perfect current when using open source leshan server

IoT Modules LPWA Module
1

Here is weird behaviour we are facing in below case scenarios

  1. Failure Condition: The module successfully registers with and exchanges application data with a custom LwM2M server based on the Eclipse Leshan framework. Following this transaction, upon attempting to enter its deep sleep state (Power Saving Mode, or PSM), the module exhibits an elevated quiescent current, significantly higher than the manufacturer’s specification. (More then deep sleep Varing between 3 uA to 40 uA) (Enter Deep sleep urc is present and At log for deepsleep is given below) Also if we after deepsleep rewake up device by using tx pin of host then device perform Exit deep sleep and when it re enter to deep sleep it current is as expected
  2. Success Condition 1 (Custom Server): The module performs only the initial LwM2M registration and subsequent update procedures with the same custom server. No application-level data is exchanged. In this scenario, the module successfully transitions into deep sleep and achieves the expected low current draw.

Success Condition 2 (Public Server): The module connects to the public, open-access Eclipse Leshan test server (leshan.eclipseprojects.io). It performs both registration/update procedures and application data exchange. In both instances, the module correctly enters deep sleep and exhibits the nominal low-power profile.

Sleep Mode sequence
AT+CSCON?

+CSCON: 0,0

OK
9/3/2025 13:12:23.748 [RX] - AT+CPSMS=1,“00101100”,“00000010”

OK
9/3/2025 13:12:23.860 [RX] - AT+QNBIOTEVENT=1,1

OK
9/3/2025 13:12:23.972 [RX] - AT+QSCLK=1

OK
9/3/2025 13:12:24.115 [RX] -
+CEREG: 1,“A028”,“0DDA1EB5”,9,“00000010”,“00101100”
9/3/2025 13:12:30.038 [RX] -
+QNBIOTEVENT: “ENTER PSM”
9/3/2025 13:12:34.001 [RX] -
+QNBIOTEVENT: “ENTER DEEPSLEEP”

we have check at AT log no difference and EPAT logs are also there .
My question is that how device behaves differently even after getting Enter deep sleep urc is received .Is there something that we are missing , because to get expected current either module need to exit froom deep sleep and with in few sec Enter to deep or after Tau t3412 expire and meter automatic ping the network .
as given Below

After Deep sleep we give forcefully change tx state so that trantion on RX of module make it wake from deep sleep
9/3/2025 13:12:35.683 [RX] -
+QNBIOTEVENT: “EXIT DEEPSLEEP”

9/3/2025 13:12:45.737 [RX] -
+QNBIOTEVENT: “ENTER DEEPSLEEP”

2

According to your description, after the print “+ENTER DEEPSLEEP” at this moment, did the power consumption not reach the lowest level?

3

Yes you are right it does not meet minimum, lowest current

4

I suggest you measure the voltage of VDD_EXT. If it remains at 0V continuously, it might be that the additional power consumption is coming from other circuits.

5

Yes vddext is 0 and even we have removed all Rx Tx pin too this behaviour is ok on one server when data exchanged and but when data is exchanged on other server even after Enter deep sleep current doest not fall, all pin voltages are as recommend, weired situation

6

You need to capture the debug log and conduct a thorough analysis.

7

And I have already sent you the tools and the instruction manual. Please check them out.