Does the EG912UG support PSM? I am referring to the document EC200U&EG800G&EG91xU&EG915G Series Low Power Mode Application Note version 2.1 which seems to indicate it is supported. If I issue these sequence of commands:
I can see the PSM timer is active and decrementing using the command:
AT+QNWCFG=“psm/timer”
+QNWCFG: “psm/timer”,1200000,1023825,300000,123825
OK
The final counter decrements to zero, but the network LED never turns off & power consumption never goes down, even if there is no traffic whatsoever on the UART. I get similar results using the CPSMS command, even though it is not attested for the EG912u.
The documentation is confusing. The release notes say:
GENERAL Modified AT+QSCLKEX and its functionality is no longer supported.
but also in the same document, that PSM is supported since A03:
From your log, it can be seen that the current version of EG912U supports the PSM function. However, due to the excessively long activation timer, it takes a very long time to enter the PSM sleep state. Perhaps you need to negotiate with the SIM card server about the activation timer duration.
Hi, thank you for your reply. I did wait until timer expiration (which as shown is only 5 minutes) and it did not shut off. I’ve since figured out that the module is preventing sleep because USB was plugged in. I have fixed that by using an external power supply instead. Now I have a new problem.
When I enter PSM with QSCLK=3,…, the module enters sleep mode almost immediately and does not wait for the requested active_time expiry (5 minutes). This seems incorrect. It also doesn’t wake by itself after the TAU expiry (20 minutes). It seems to be ignoring the active & TAU timer values.
As per the documentation, “The timer value issued by the network can be obtained by AT+QNWCFG=“psm/timer””. These values are correct so I don’t believe this is a SIM / carrier problem if the documentation is correct.
I checked the PSM pin and it does not seem to be actually entering PSM mode. I am sure my carrier and SIM support it. What could be the problem? I have very limited tools to diagnose, since QNWCFG=“psm/timer” is the only documented method for verifying carrier confirmation on this particular part, and it seems to be correct. CEREG? is not reporting TAU. URC reporting for PSM is not supported via QCFG=“psm/urc”,1. QPSMS? is not supported.
I am seriously questioning whether the 912U supports PSM at all. That it seems to respond to some commands is not enough proof. They could be responding but inoperable.
Can you please provide me a list of 91x series modems that officially support PSM and/or eDRX? Should I be using the 915Q or 916Q instead? We are trying to evaluate which parts will work for our application and it’s very difficult information to find.
I’m certain that the EG912U supports the PSM function. Additionally, through your log analysis, the EG912U successfully obtained the TAU and active timer for PSM. However, the current power consumption you are measuring should be the power consumption in the normal sleep state, because the active timer time obtained by the EG912U is 5 minutes. You need to observe the power consumption after more than 5 minutes.
Is measuring the current the only way to tell? As mentioned above, QCFG=“psm/urc”,1 is not supported, QPSMS? is not supported, CEREG? is not reporting TAU, the PSM pin is not getting asserted, and while QNWCFG=“psm/timer” returns values that match what I asked for, the timers don’t seem to reflect what the modem is actually doing.
While it’s great to confirm that PSM is active, I also need to integrate this into a system eventually. I can’t just have an ADC monitor the modem in sleep to see if the modem has woken itself up. I need some way to tell from the UART/AT interface or GPIO that it has gone to sleep and some way to tell that it’s woken back up. As it stands now I can’t predict that. The “psm/timer” values don’t match what the modem is doing.
For instance, I mentioned that if I set a 20min TAU, the modem didn’t wake up at the 20min mark. I did some more extensive testing for a variety of TAU values between 20 minutes and 2 hours, and active timer values between 5 seconds and 5 minutes. I let the test run long enough to ensure that I was looking at periodic behavior. In the 20 min TAU case it would eventually wake up at the 1 hour mark, every hour. If i requested TAU=60 minutes, it woke up every 12 minutes. For TAU=90 minutes it woke up once and then never went back to sleep. The behavior doesn’t seem related to the requested TAU/active values at all and I’m not sure how to tell what it’s actually doing.
Besides measuring the current, is there any reliable way to tell whether the modem is asleep?