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1  Products / Arduino GSM Shield / Re: Connecting to GSM/GPRS unstable, eventually hangs on: July 20, 2014, 09:00:22 am
I've been running my own modifed GSM shield for a year, and as people have discovered the libraries works in the lab. But once out there in the wild, the things fail. If you look really deeply into the M10 datasheets the reset line of the module should be connected to the Arduino. There are some network issues that simply hangs the modem in an unknown state. Typically if a GPRS connection is lost and not disconnected properly.

My take on this is to connect the reset line to an IO pin of the Arduino, then modify the libraries as been posted here, but also to insert a watchdog timer. The built in watchdog is to fast with just 8 seconds maximum so either a software interrupt that makes it longer or a hardware watchdog. I've used both so far...

If I were to do this project again I would not use the Arduino GSM libraries but just raw AT-commands. Every communication step can and will fail and I need to adjust the timeouts on these events.
2  Products / Arduino GSM Shield / Re: Mellis DIY Cellphone on: December 07, 2013, 11:56:14 am
I built the phone this spring in a workshop done by a girl called Tricia, and it is really possible to do it. David C. instructed us on how to solder the thing. After that I learned a new thing that made everything easier to solder - The copper planes are quite big so the board needs to be preheated for an ordinary solder iron to be soldered. Preheating is the key. I bought a special heatblower that works from under the board, but anything similar should work.
3  Products / Arduino GSM Shield / Re: Code hangs in interrupt when there is poor GSM signal on: December 07, 2013, 11:47:33 am
amarofarinha - You need to connect a reset line to the modems emergency shut off pin. This is not included on the GSM board, but it clearly states this in the Quectel hardware manual. There are some GPRS edge cases when the module tries to shut down GPRS but the network has already bin lost and then there is no way to connect to it at all. Without removing the power to the board, or pulling this special line low.

In the arduino sowftware I have an input pin that I set low. Then turn it into an output pulling the emergency shutdown low. Then returning it to an input again. Never drive the pin high as an output as the voltage levels are wrong.

This problem can only be seen in some special physical places. It works without it for months at some places and just a day or two in some. It is not just a bad signal, it is a network related error when the gprs connection can not be disconnected correctly from the network.
4  Products / Arduino GSM Shield / Re: GSM SHIELD suddenly stopped working on: December 07, 2013, 11:11:34 am
There are so many ways it can break...  hardware can break, but most likely it is your code that messes with something.

Try downloading some of the basic examples again and see if it works?!
5  Using Arduino / Project Guidance / Re: Autonomous wind meter with GSM module - Battery-Solar? on: December 07, 2013, 09:28:01 am
From my experiments we have moved from car-deep cycle batteries (~20mA continously) it run for 10 months.
We now use a 6Ah LiPo battery and some heavely modified arduino boards. One extreme case is to put the units under ground for three years and do a measurement every day, report it and then go back to sleep.

LiPo batteries should not be charged in minus degrees Celcius as they freeze and when charging release pure Lithium inside of them, which might turn into a fire hazard. They are ok to charge in plus degrees.

For a starter project that is not intended to be mass-produced I would recommend the car-battery approach. They are expensive and big, but easy to get started with.
6  Products / Arduino GSM Shield / Re: GSM Shield problem - reset during registration on: August 11, 2013, 06:54:02 am
The ethernet stack and the gprs shield both consumes RAM memory which is very limited. Once there is no memory left, random issues occur often followed by a crash and reset. This would be my first bet in this case.

Google and check for code that tests for low RAM memory as memory problems are rather hard to find out on the Arduino.

We had to move a gprs application to the ATMega 1284 to be able to use some extra libraries for i2c and one-wire sensors.
7  Products / Arduino GSM Shield / Re: Code hangs in interrupt when there is poor GSM signal on: August 03, 2013, 04:23:19 am
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...
8  Products / Arduino GSM Shield / Re: GSM Shield availability? on: August 03, 2013, 04:04:58 am
Adafruit and Sparkfun are US companies. Since this is a GSM module it will only work in 2G GSM networks operated by AT&T in the US (please correct me if I'm wrong) who a year ago decided that they will not replacing faulty 2G GSM equipment, but let the network die slowly. I.e the module might not work in your particular neighborhood.

Since you are supposed to certify your GSM equipment with the operators in the US, and AT&T no longer accepts 2G equipment it cannot be sold in the US...

However, they are available from and I guess it should work in the US with AT&T, you might wish to try it but there are no guarantees.

3G modules are usually about three times more expensive, but maybe there is a 3G shield avavilable from third party companies? The cost of the US operator certification is still a major hurdle for the small volumes produced. (~20.000-200.000 USD) They would work, but you can not sell them on a larger scale as the US operators might decide to ban them in their networks.
9  Products / Arduino GSM Shield / Re: How to handle these devices on: August 03, 2013, 03:50:17 am
If I remember I needed to remove the coils for a real antenna to work with the module.
You might need to remove the patch antenna (Hard to remove as it has five solder points, I used a heating gun and force) and also the two coils that goes from the antenna wire to GND. Do keep the small capacitor that connects the antenna wire to the antenna wire (look at the board and hopefully you will understand what I mean).

My experience is that the Quectel module is very forgiving. You basicly just needs the PCB trace and it works. (might not be within specs but... it does seem to work when I play in the lab)
10  Products / Arduino GSM Shield / Re: GSM Shield powering on: August 03, 2013, 03:42:46 am
Check which GPRS sending mode you are using. If you transmit just one out of the possible 8 timeslots you ease the load on the power supply. It will be a slower transmission but safer, power-wise. For the Quectel module there is a special (non-standardised) AT-command to set the GPRS mode, your module might have a similar command.
11  Products / Arduino GSM Shield / Re: GSM shield is not connecting to the network on: August 03, 2013, 03:36:47 am

I had tried TEST GPRS and the debug output also i have attached below. The sim is not connecting to the network. I have give external pwer supply of 12V/1.5A but still the problem remains same. Please help me out.

Connecting GSM network...AT%13%
0 9>AT%13%%13%%10%OK%13%%10%
9 44>AT+CPIN=1234%13%%13%%10%+CPIN: READY%13%%10%%13%%10%OK%13%%10%
44 75>AT+CGREG?%13%%13%%10%+CGREG: 0,2%13%%10%%13%%10%OK%13%%10%
75 106>AT+CGREG?%13%%13%%10%+CGREG: 0,2%13%%10%%13%%10%OK%13%%10%
106 23>AT+CGREG?%13%%13%%10%+CGREG: 0,2%13%%10%%13%%10%OK%13%%10%%13%%10%Call Re
23 54>AT+CGREG?%13%%13%%10%+CGREG: 0,2%13%%10%%13%%10%OK%13%%10%
54 85>AT+CGREG?%13%%13%%10%+CGREG: 0,2%13%%10%%13%%10%OK%13%%10%
85 116>AT+CGREG?%13%%13%%10%+CGREG: 0,2%13%%10%%13%%10%OK%13%%10%
116 19>AT+CGREG?%13%%13%%10%+CGREG: 0,3%13%%10%%13%%10%OK%13%%10%
19 50>AT+CGREG?%13%%13%%10%+CGREG: 0,3%13%%10%%13%%10%OK%13%%10%

This means that you are not accepted by the network you try to attach to. I have seen this twice:

1. We had a faulty power supply on the GSM module. It would attach to the network, then reboot, then try to attach, then reboot. The modules IMEI number was blocked automatically by that operator even though we replaced the power supply. The module can be used in other operators networks, but not in the network that blocks it. (This was not with the arduino GSM shield btw)

2. There was an electrical fire in an operators control switch, that operator network was not working correctly for a week in that city area. When the module tried to connect to a particular basestation (very good signal strength) we got the 0,3 status, while it attached to another operators cell tower (we used roaming sim cards) it went fine. We had to point the antenna in another direction and then it attached randomly every one out of ten attemps to the other operators cell tower. This was with a modified Arduino GSM shield.

My suggestion is to use another network operator SIM card to test it out. Your module might be forbidden in your current operator network. Also be aware that some operators infrastructure, like the blocking database might be shared between countries. Telia Sweden and Telia Denmark shared their database which we discovered so we had to throw away that module. Also be aware that the SIM cards that are shipped with the GSM modules are roaming, i.e if you use them, you never know which local operator might be used, and they might have locked you module from entering their particular network before the traffic reaches Telefonica.
12  Products / Arduino GSM Shield / Re: arduino program code +gsm for industrial automation.HELP NEEDED on: June 23, 2013, 01:43:14 pm
Hi, the loop might send an sms, but there is no end of the sms as it continously loops over and over again. Thus you would send a string of sms as long as the signal is low...

If your planning to sell the thing I could help you out on a commercial basis as I do this kind of things for a living, but otherwise I suggest going to local hackerspace as it is rather trivial for someone who has done it before, but requires a lot of reading and testing for a beginner and getting the help of a real person is usually much more fun!

13  Products / Arduino GSM Shield / Re: GSM shield hangs when reset/uploading code during GPRS connection on: June 23, 2013, 12:33:34 pm
Regarding transparent mode to talk to GSM module - Look up Arduino Phone project on Github. This sketch does it -

Also have a look at the projects homepage for some other fun things to do with the modules!
14  Products / Arduino GSM Shield / Re: Timestamp from GSM Network on: June 23, 2013, 12:24:29 pm
Try googling GSM_Location_ATC_V10 which seems to be floating around the net. It gives

AT+QIFGCNT=0 //Choose the contect 0 to activate GPRS/CSD context for the TCP/IP service.
AT+QGSMLOC=2 //Get the time

That will give you the current date and time.

Try AT+QGSMLOC=1 and you will get the longitude and latitude as well ;-) There is a AT+QGSMLOC=8 that should get better precision, but it's not working for me...

15  Products / Arduino GSM Shield / Re: How can I stop gsm.begin()? on: June 23, 2013, 12:17:19 pm
Quectel claims in some datasheets that you should at least send three "AT" commands to the module before trying to do anything else...

It might be that it tries to do autobauding, which might looks at the bit-patterns of the AT and then tries to guess the baudrate... but that is just my guess. In that case it should be possible to send the module an AT-command to set it to a fixed baudrate, and then save that setting in the module... otherwise there is another problem. I have seen some strange things when using the slow-clock mode of the modem along with the DTR signal, but that is not really related to this issues I think.
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