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We pay roughly 7 USD per the modem now. That price will increase to 25-30 USD with the 3G/4G models that I am aware of. This will make our product too expensive. The extra data cost is currently not an issue.
We currently have a product that uses SIM800 which is a 2G GSM/GPRS module. It works beautifully, but in certain parts of the world, they are closing down the 2G network, so we are looking to switch to either 3G or 4G.
We found that the price of a SIMCOM modem with 3G or 4G is at least 4 times...
I am using a SIM900 modem, and I use the command AT+CENG to get info about serving cell and neighboring towers in order to estimate the location of the modem. I would like to use TA from all neighboring towers for improving the accuracy.
The parameter TA (Timing Advance) is only given for the...
Hi,
I think this problem can have many different causes. In my case, I think the root of the problem is noise from the antenna onto the SIM card. It seems to happen more frequently if I communicate before receiving "Call Ready".
Please upload your schematics (or send PM to me). If possible...
Did you solve this one? I am also looking for this information. I have found several sites - for example this one:
**broken link removed**
The problem is that I have not found one that is up to date.
Another way to go is to use the following list (which I think is at least almost up to date)...
SIM PRESENCE error can be several things. Are you sure it's not a mechanical issue with your SIM-holder? You may try to connect the SIM_PRESENCE pin to GND just to check this.
Which message does the SIM900 give when it doesn't register with the network? It would also help if you can upload your...
The problem was solved with the help of GSM Man: If you communicate with SIM900 before the module has sent the unsolicited message: "Call Ready", then you might get this problem. I now wait to communicate until after receiving "Call Ready" from the module, and all problems are solved.
Hi,
I'm using a SIM900 module, and usually it works fine, but lately it has started giving the error "+CPIN: NOT READY". As soon as I get this message, the voltage on SIM_VDD drops to 0V. The problem is intermittent (i.e. it happens only sometimes).
It seems to happen more often on 3V SIM...
Hi,
I have the exact same problem. Did you solve this? If yes, please share your solution.
I am using SIM900, and I get this error (only sometimes, and only on some of the modules).
I believe it has to do with power to the SIM card. The attached image is from the documentation. It is...
Hi again,
I have done more investigation (double checking resistors, decoupling caps and firmware) and I suspect that something in the layout is just not designed optimally. In debugging I can see that the reset is because of the clock, and not because of power down. The traces from MCU to...
Thanks! I do have power supply decoupling and adding more didn't help. Also, removing the 10M resistor between XTAL1 and XTAL2 didn't help.
I'm using a watchdog and interfacing to a GSM modem. After resetting, MCU waits 5 min and then switches on the modem. This reset is what happens a little...
Thanks for your answers!
I think I have located the source of the reset. I have a crystal connected to XTAL1 and XTAL 2 as in the picture (except I use 32.768 kHz and 6p caps)
When I touch either side of the resistor with something that has a certain capacity (either long wire or with fingers...
I have an C8051F921-GM MCU that seems to be either losing power (probably only dropping out for short time) or is being reset by RST pin being pulled low. Batteries are ok.
1. Could it be because pullup resistor is too big? I have 100k pullup to RST while datasheet recommends between 1k and 5k...
Thanks for the three options. The first one is too expensive to put on this product. The second one seems like a good option. I have seen many of this type, and from what you are saying, it sounds like they are all equally good if the cable is short. A few questions:
1. Is it correct to say that...
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