HL7800 sometimes not entering PSM mode

IoT Modules HL78
1

Hello,

I am entering PSM hibernate mode by following this schema inside my application:

AT+KSLEEP=1,2 // once at start-up

STEP 1
When my device wakes up for next transmission, WAKEUP pin is pulled HIGH and I also give the command AT+CPSMS=0 just in case. The device transmits data.

STEP 2
After data transmission I give the following command
AT+CPSMS=1,"01001010","00000001"

STEP 3
then I wait for +CEREG: 4 and after that I pull the WAKEUP pin LOW.

then we go back to STEP 1 and so on…

This works 95% of the time but sometimes the modem will not go to hibernation after STEP 3 and current consumption is close to 40mA.

Here is a log of the CEREG replies that would indicate that this CEREG: 4 is not an out of coverage indication:

ENTERING MODEM HIBERNATION... {OK}  {+CEREG: 1,5} . {+CEREG: 1,5} . {+CEREG: 1,5} . {+CEREG: 1,5} . {+CEREG: 1,5} . {+CEREG: 1,5} . {+CEREG: 1,5} . {+CEREG: 1,5} . {+CEREG: 1,5} . {+CEREG: 1,5} . {+CEREG: 1,5} . {+CEREG: 1,5} . {+CEREG: 1,5} . {+CEREG: 1,4} OK

What am I doing wrong?
firmware version is 4.6.9.4

thanks

2

Is this the correct procedure at least?

thanks

3

do you have USB connected?
Can you disconnect the UART fully during the sleep mode?

I have one experience that if I type some characters in UART, it can help to go to sleep mode, not sure if it is the same case as yours.

4

Hi @jyijyi,

UART COM port is being disabled after CEREG: 1,4 indication and after I pull the WAKEUP pin LOW.

I am not trying to go to sleep mode but into hibernation.

thanks

5

you can try to type some character in UART and see if that helps when it cannot go to sleep mode.

6

Typing characters in UART does not help.

The modem randomly refuses to go to hibernation still and when that happens the LED I have connected (with the command AT+KSYNC=2,2) stays ON after CREG: 1,4 and the modem does not respond to AT commands.

Any more ideas?

7

Is it vgpio pin keeping high?

8

When that happens then yes, VGPIO is high at 1.8V

Also, when it doesn’t enter PSM mode, toggling the WAKEUP pin doesn’t help either.

9

@jyijyi,

One more thing, it seems that the modem might be getting stuck as the UART1_CTS pin stays HIGH when this strange behaviour occurs. That could be useful though to identify in software when this happens.

10

Hello
Do you still have this problem or have you already found a solution?
I have an HL7800 to communicate via NBiot and have the same problem. Most of the times the modem goes to hibernate after PSM, but sometimes it does not. Also toggling the wakeup-pin does not change the situation, and the vgpio also stays high.

After sending the next message, the modem goes to sleep the normal way.
I am using firmware 4.7.1.1

11

Hi,

What do you mean by this?:

I haven’t managed to make this work and have to turn the modem off when this happens .

12

I meant that when I do the normal sequence of transmitting an message again, the sleep after PSM usually does work.

energy_usage_HL7800_sometimes_not_off_in_PSM
energy_usage_HL7800_sometimes_not_off_in_PSM971×836 72.5 KB

In the attaches image there are 2 situations. In the above situation there is a message sent. After that the modem goes to sleep, and some time later another message is sent. Like it usually works.

In the situation below, a message is sent, but the modem stays awake for some reason. The current is also about 40mA in that case. But after the next message, the PSM does work again.

13

Oh ok, so same behaviour as me.

What I do is monitor the UART1_CTS line and if it stays high after the CREG: 4 message then I just turn the modem off. 40mA is catastrophic…

You might have to play with the timing there a bit as the CTS line doesn’t go low immediately after the CREG: 4.

14

Thanks for the quick responses. At the moment I monitor vgpio to detect this situation. It seems this signal changes at about the same time (in the same second) as the cts.
I think your way of powering off can indeed be more efficient than sending a new message, so I will also look into that method.

15

Oh yeah I remember now about VGPIO, I don’t have it connected in my PCB.

What are you using to monitor the consumption in your screenshots?

16

I use a Nordic power profiler kit II (Power Profiler Kit II - nordicsemi.com) for the consumption monitoring.

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