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[on:]

Hello,

I am using the GSMShield on a custom pcb. This works perfectly when I was developing the code, one of the tests is how the code responds when the GSM signal is lost. Another test is how the board responds with poor GSM signal. This is where a problem occurs.

When the GSM signal is lost I reboot the board. When the board starts with a poor/no signal the gsm.begin() function hangs. (I previously had problems with the power supply but I solved these).

After some digging arround in the code I found in GSM2SoftSerial::recv() a call to mgr->manageMsg(thisHead, cb.getTail()); when the buffer is full, line feed or space.

In GSM3ShieldV1ModemCore::manageMsg I find the implementation which specifies that is we are not debugging we are going to manage the message in the interrupt.

When we manage the response GSM3ShieldV1AccessProvider::manageResponse is called which calls GSM3ShieldV1AccessProvider::ModemConfigurationContinue which will send a new request.

Since this chain happens during an interrupt the normal code will not run untill a good GSM signal is detected. This looks like gsm.begin() hangs.

Can somebody confirm this behaviour? Is there a good work around?

thanks

[Reply #1 on:]

As a hack I have added a counter in GSM3ShieldV1AccessProvider::ModemConfigurationContinue() which limits the number of tries to get a connection. I think a better solution should be implemented in the library because this bug can create not responsive board. Especially with this GSMboard it is likely the boards are in a remote place.

[Reply #2 on:]

There are a lot of network related edge-cases that introduces strange problems that locks the modem. I did solve this one, but can't find my answer on the forum. Glad you figured out a way too.

The GSM shield hardware, software and the Quectel module itself, has some severe problems for real world projects... I'm thinking of re-writing the needed AT-commands in a very simple C style with individual timeouts for each command. Our latest discovery were that the Quectel module might take several minutes of trial and error to find a network it can use. A two minute timeout was not enough when the first network refuses it...

[Reply #3 on:]

Hi armin,

I have exactly that problem. The module keeps looking for connectivity indefinetily... can you tell us the way you solve the problem by modify the librarie?? That will be much appreciated.

Thanks!

[Reply #4 on:]

I have the exact same problem. Few days ago my Arduino UNO + GSM shiled was working just fine. It now decided not to work for some reason. The NET led keeps blinking, at a higher frequency (than when it is actually connected to the GSM network). It does this for hours and hours without any connection. I have searched the forum and tried everything other have suggested but no luck. Ant help is appreciated. I am new to this stuff and no idea how to work with AT commands.  Thank you.

[Reply #5 on:]

I have the exact same problem here. I'm doing a beehive monitor system and my arduino is at a poor network signal place.  I have even made a hardware watchdog to reset arduino in case it hangs at this point. It has been working that way fine except for 2 times, when not even after a reset it can stablish connection again. It must be hard reestarted to continue. As i am 250km far away from the system when it happens its very anoing :-( .. I have not had the time to check the library code. It would be very nice to have a solution or good workarround for this problem. .
kind regards,
Amaro Farinha

[Reply #6 on:]

I have the same issue...and I believe that there are some libraries of GSM that need to be rewritten...