Thanks for your kind words.

Thanks for the idea, Ian

Good to hear

Hi @Samir, Great to hear. Can you guide me if you have used any other component like diode or just capacitor in series with 5V pin of ESP32 ?

That's interesting about DTR - normally in serial setups, the terminal raises DTR to tell the modem it is active. I'll experiment with mine.

Thanks for your answer Martyn. Yesterday when I set up the test circuit I left DTR open without giving it a second though, but after a whole day banging my head against the wall I tried what we call "lanzar un flechazo" (to throw an arrow, in spanish, more or less equivalent to "Hail Mary pass") without much enthusiasm, but it worked: rock solid connection to PuTTY. Moreover, I just confirmed it just now: I replaced the module to test something else and started getting spotty serial communication (sPuTTY?). After a coffee I.V. I realized that I haven't connected this module's DTR to ground. Connected it and problem solved.

@@fik_of_borg Very interesting. I found an app note (cdn-shop.adafruit.com/product-files/2637/SIM800+Series_Serial+Port_Application+Note_V1.01.pdf) that says that DTR is for sleep mode; DTR high = sleep. Depending on the setting of AT+CSCLK, the module has sleep mode enabled or not. I must have got lucky.

Downloading to my "arsenal", thanks!

It's right across the power pins +5V and GND. You can think of it as a reservoir that holds a bit of charge to supply when the module draws its maximum current. The yellow cap on the board is doing the same job, but in my experience that just isn't enough.

Thanks!

De nada.

I think so. What I understand is that the RING pin on the module will pulse low briefly when a call is received. You could detect that pulse on an Arduino pin.

@@MartynDavies thank you!.. I've ordered some parts going to give it a try ...

Yes. You can't send texts unless the SIM is active and funds are available.

I have a SIM900 that has been running for several years in my shed - basically it sends me a text if the power fails. This has been very reliable, and the system has only suffered a minor failure in that it doesn't know the correct time anymore (which I think is because the telco doesn't send the time any longer). The SIM800 I haven't tested in the same way, but it has fewer components on board (than the SIM900).

Thanks a lot for your reply. I am sending data to ThingSpeak.com . I am also able to send data without using this command: gprsSerial.println("AT+CSTT=\"www\",\"\",\"\""); Do you think this command is always required to be included included in code ?

Yes, the bigger the better

I would experiment with the character set, e.g. the AT+CSCS command

I haven't tried to make calls with this module, although I saw there was an audio input/output. As far as I know, it's just for mic/speakers, so Bluetooth I don't think so.

@@MartynDavies Thankful🙏

This one is very cheap and small, and offers good functionality as long as GSM is enough for your needs. Notably GSM has quite a crappy data service (GPRS), so if you really wanted to send a lot of data, then some other solution is probably needed. 3G (or 4G) modules are much more expensive. Ultimately, GSM will disappear (and the frequencies will get reallocated to 5G), so many IoT application will have to change to NBIoT, LORA, Zigbee, WiFi or other modern radio choice.

I was using 9600bps with mine, and this is my normal starting point. You can try ATE1 to see if you get any echo back from the module. Also AT&F0 to try to reset to factory condition. Make sure you have RX on your PC attached to TX on the module and vice versa. If I remember right, this module displays some text on power-on, you you should be able to check whether you have the RX pin connected right. You could try to use an Arduino as the connection to the module (see www.arduino.cc/en/Tutorial/BuiltInExamples/SerialPassthrough), which is sometimes a help. As a last resort, get a second SIM800 module, in case the one you have is genuinely broken. Low cost logic analyzers (e.g. www.ebay.co.uk/itm/154896110001?hash=item24108711b1:g:1aAAAOSwutpdmKNE) can be a help in capturing/analyzing serial data.

@@MartynDavies thank you Martin! I appreciate your answer in details.. I'm going to try

The SIM800 only has radio interface for 2G/GSM, however in many places the cellco offers both 2G and 3G services using a single SIM card. The SIM is really just a unique identity that the cellco can use for billing.

@@MartynDavies It supports G2

Hello bro The problem is sim800L working(there light), but when i call it from my phone doesnt have broadcast. I tried alot of antennae types, and sim card 2G and 3G, but doesnt work. How can i fix it? I mean how can i get the brodcast?

@@mohammadatiah735 The module flashes slowly (about 2 seconds) when it is properly registered on the network.

@@MartynDavies I only have a broadcast problem

Yes, I have one on order.

I'm sorry, I don't know, but if the Airtel SIM will work in a 2G phone, then it should also work in one of these modules.

I don't really know NVRs, but I'm supposing if it has a serial port, then it could be connected to a GSM module. You might need a MAX232/DB9 module to give you the right voltage levels and connector (these are very cheap).

I would try stepping through it in the serial monitor to make sure you have the right sequence. Also remember to have the country code in front of the number - this module seems to expect the full number including country code. If you are running a program on Arduino and want to check what the module is receiving, you can set ATE1, which will cause the module to echo back any characters you send. Print them all out to the console so that you can see what's happening.

@@MartynDavies actually it worked for a week now I don't really understand what is going on. On the IDE it showed me that the message has been sent but the receiver didn't get any message

@@wouladjecabrelwen1006 Could it be that there's no credit on the account?

@@MartynDavies I have check it and I have recharged my credit card tomorrow I'll check it again

I really had no credit too. Always check first your prepaid:-)))

you'll need to generate the timestamp in your program, and use that as the text to go in the AT+CMGS message

I found it ok, I guess it depends how close you are to the cell tower of your chosen provider.

I'm talking to the board via its serial port here to redirect to a browser you need an application rather than a library.

@@MartynDavies actually i guess, there is protocols/driver softwares for that as there is old printers or modems for serial ports, and as sometimes serial devices ewen work with usb ports. it may be possible to redirect network connection to network interface on os. probably there is a driver interface protocol for each os. Which can be used to emulate using arduino, and i thint itll work if there is no strict rules for timeout times. Anyway drivers too are some kind of application too ;) May be emulating a vnc server it can be done , but doesnt seem easy. ;)

Definitely 2G / GSM only, but this one is quad band, i.e. 900/1800 Mhz (for Europe) and 850/1900 (North America). The fussiness of the power supply is the thing that makes these hard to use.

You don't see any +CMT indications from the module?

@@MartynDavies Yes , but when I do that , VCC sim800L --- 5V arduino and GND sim800L ---GND arduino it(s work (send, receive, call, displat AT command) , but As you know voltage of sim800L is 3.7-4.2 V ?

@@attilahcen8194 If you put a diode in series from the arduino +5v towards the sim800, this will drop about 0.6V, which should be ok for the module.

@@MartynDavies put Capacitor between GND and +5V sim800L

Check that you have the RX/TX the right way round. Normally TX on the module goes to RX on the serial interface board (or Arduino or whatever you're using). Next try all the speeds with your serial interface in turn (9600, 19200, 38400, 57600, 115200, slower ones are not normally used - 1200, 2400, 4800). At each speed send AT {enter} to see if anything comes back. Try also AT ctrl-J; this is line feed (LF) sometimes used instead of carriage return (Enter or CR). At each speed you can also try powering the module on and off, as sometimes modules write out some text on power-on; this can help to figure out if at least RX is plugged-in right. If this doesn't work, try something instead of your serial interface; they're quite cheap, and it's useful to have a few different USB adapters to chose from. You can also use an Arduino as a serial interface; if you look at the software serial examples there is a piece of sample code that reads from your PC and sends (TX) to a soft serial port, which you can connect to the SIM800. Once again this gives you a lot of scope to try different speeds and LF instead of CR. You can also try a login analyser - the big brand is Salae, but there are many cheaper generic devices available on ebay. With a logic analyser you can listen on the pins, and it will visibly decode any serial traffic that it captures.

The first 0 means that the signal is very weak indeed. Check the antenna connections are good - perhaps get next to an open door or window to see if you can get the level any higher. Did you fit the extra capacitor? I find these modules don't work at all well unless you have a big cap close by.