Hi @John Bobbs, thank you for the kind words. Cheers.

Thank you Mahe. God bless you too.

thank you @Rameshkumar.

@Stuart Weldon, wow that's great. Thanks.

@@TechToTinker could you please suggest a way of programing the switch it only send one text message whilst the switch is pressed.

@Stuart Weldon, what do you mean?

@@TechToTinker if you continually hold your switch in your demo it sends multiple messages, I would like it to send only one text,

@@stuartweldon8333 I am thinking to do it like as follows: #1. Detect if switch is press. if sw is press and sms_sent=0, send sms and set sms_sent=1 #2. Detect if switch is release if sw is release, sms_sent=0 This way you can avoid sending multiple sms when switch is held press.

@hieu pham, glad that it helps you. Thanks.

Most welcome. Thank you.

@Yogesh Sonawane, Im not sure what you want to achieve, but have you seen this video already? ukposts.info/have/v-deo/iaWWnYKPg3yH1YE.html

@@TechToTinker yes sir i had seen this video, and by using the same code i made project but system is accepting all calls coming to it, so any one can make our led ON or OFF by calling the number , So how to make it to receive only my number and all others will not to receive. Thank you for your reply, Loved your work sir.

@@yogeshsonawane4113 you can do that by adding additional condition check before executing an action. The additional check of course is the checking if the receive command comes from specific number. Please let me know, if you need further help. By the way, thank you for the kind words. Cheers.

You are welcome @KMV. Does it work?

what is configuration of your switch? Active-LOW? Other pin is connected to ground and internally pullup To check: if switch == LOW or Active-HIGH? the pin connected to Uno has pull down resistor going to ground the other pin to VCC To check: if switch == HIGH

Active low switch sir

ok, it means no need to change anything in your setup. How does it work?

Sir this program... bool curr state =HIGH; bool prevstate= HIGH; Unsigned long startmills=0; Unsigned long=denounce=50; Void managebutton() If==low Sir

You're welcome :). Thanks

@@TechToTinker Good eve po sir. Ano po ang dapat gamitin na simcard for this module? Gamit ko kase is yung 5G globe sim. Wala akong reply nare-receive mula sa module pero sa serial port meron po. Kahit po naka-uncomment na yung simulation..

Comment-in na po lahat ng code sir..

@@jesthonymahilum8414 I'm not sure if 5G sim cards still supports 2G. Try mo na lang gumamit ng medyo lumang sim card.

@@TechToTinker sige po sir. I'll try po maghanap ng lumang simcard. Thank you so much po sir sa reply. God bless and keep safe..

Hello Erik, if the SIMULATE_BY_SERIAL is comment out, it will work in actual and you've got it right. Else the communication with SIM800L will be directed / route to serial. Basically, I used it on development and debugging purposes to save money with sending and receiving sms. You may also use it :). Thanks and you're welcome.

3.9V is ok but Im not sure if it can provide 2A current requirements. You may verify it on its datasheet. Regards.

Hi Kyla, yes I did. I used 12V 2A power supply. You may observed it in the video.

How did you lower the output voltage po? It says that sim800L will only need 3.7 - 4.4 V? I'm afraid that I might destroy my module with too much voltage. Thankyou.

That's doable but I am not sure if the memory space will be enough in Uno. Try using ESP32 instead. You may combine the source code from both tutorial.

@Ghode scientific World, Im glad that you like it. Thank you.

1. Provide 3.4V to 4.4V to SIM800L VCC pin 2. Connect the GND pin of external power supply to SIM800L GND pin. 3. Connect ***ALSO the SIM800L GND pin to Arduino Uno GND pin. 4. Connect SIM800L Rx pin to Arduino Uno Tx pin. 5. Connect SIM800L Tx pin to Arduino Uno Rx pin. This should give you better idea to properly interface SIM800L to Arduino Uno. Cheers.

@@TechToTinker Thanks indeed. The wiring is good. The reason was that it keeps resetting was the 1000 capacitor which was under rated. I had to un solder and replace it with 2200uf. Now it registers to the network straight away. I wanted to share this issue with you in case someone else faces the same problem. Thanks again for your prompt reply and good support. Wish you all the best.

Hi @Yawar Saeed, I'm glad that you like it. Your suggestion is appreciated, it is a good idea. Lets see in the future if I could come up with this. Cheers.

You are welcome @Ranel Briones.

Hi @jimy, I would think a little bit different for that to simplify the burden in coding. What I would suggest is to continue checking and parsing the sms as usual. Then for the security, only display the message after correct password entry using 3x4 or 4x4 membrane switch. Or you may use RFID cards as an option. By the way, thank you for the kind words.

You may refer to this for the password entry using membrane switch array: ukposts.info/have/v-deo/hoCbaXiEjXer0oU.html

and with this for the RFID: ukposts.info/have/v-deo/jpendXqsmYeo1as.html

hi @Julius Albalos, the code assume an ideal environment. Basically, the SIM800 will try to reconnect by itself to a known network (independent) when network problem occurs. However, problem occurs when you try to send sms while no network because it will fail, and its not handled in the code. I would recommend to check if the sim800 is currently connected to a network using the CREG AT command and handle it accordingly. Hope this helps. Cheers, George Bantique

Hi @Sky Cullen, SIM800L is a GSM module that needs a 2G support. Any SIM cards(i.e. 3G, 4G, 5G) should be backward compatible to 2G but if your country no longer have 2G, SIM800L will not work. I would suggest to look for other version of 3G module, of course that will be more expensive compared to SIM800L. If you look for SIM8xxx other models, the source code should work without modification. Regards, George Bantique | tech.to.tinker@gmail.com #TechToTinker

@Yawar Saeed, simulate by serial is mainly use for debugging the source code. What happens is when you use the simulate by serial, you as serial will act like sim800

@@TechToTinker Thanks for your prompt response. Yes, I tested the same & it works fine. Regarding NUM change command , I tested it also without Sim800 module , the changed New Numbers are there as long as the Arduino is power up or not reset. Can you please guide as what code modification will be required in order to save them in Eeprom until changed again by the NUM command. Once again Thanks & Kind regards.

@Yawar Saeed, you may try to follow this untested steps and let me if it works for you: // #1. include this at the top of the code: #include "EEPROM.h" // #2. in setup function, add this: for (i=0;i

What should happen is, every time the default number is command change, it will be saved at eeprom and will be read from eeprom every reset or power up. Rregards.

@@TechToTinker Thank you very much for the code. I will give it a try and get back to you for the update.

#1. add this code: void callNumber() { // replaced ZZ with your country code // replaced XXX with mobile number // be sure not to delete ';' // inside the quotation marks SIM800L.println("ATD+ZZXXXXXXXXX;"); } #2. instead of sendSMS(), use callNumber() function.

Hello @Suyash, thank you. There is a portion in the source code which parses the sender's number. By searching the string 'CMT:' then 'sender_num' is parse from the SMS received. What you can do is compare it to 'default number' and if its true, then do the necessary action. Hope it helps you.

@@TechToTinker Thank you sir for response, actually I don't have a coding background. Could you please help me with the syntax and addition of code.

I tried searching "4g gsm module" and here is the 1st result: greatcometbroadway.com/4g-gsm-module/ Hope this helps.

@Rameshwar Gadekar, thanks brother.

Hi LABRADA, you may reach me through email: tech.to.tinker@gmail.com Regards,

I have not experience that, maybe your sim do it like that.

@@TechToTinker ok sir , Thanks

Hi Jhofel, gsm modules are exactly the same as regular mobile phone. Send an SMS to a certain number for balance inquiry, of course through your gsm module.

Hello @Emmanuel Jideofor, do you read anything from serial monitor? If no, you might have problem with your circuit. If you are receiving some serial dumps, you miight need to change the number written in default_num variable at the top part of the source code. Cheers.

@@TechToTinker Thanks a lot, It worked. But what if I wanted two default numbers instead of one and that it doesn't accept commands from a random number, what do I do? I've tried tweaking the code but I'm missing something. Please can you help.

Hello Emmanuel, just create another variable lets say default_num_2 and put the 2nd number Then somewhere in your code when you checks for the default_num, make it to be like this: if ( ( num == default_num) || ( num == default_num_2 ) ) { // do a task } Hope this helps. Cheers.

@hamdi ahmed, It usually happens when baud rate is not the same. Set the same baud rate to your serial monitor to 9600.

@@TechToTinker of course I used the same baud rate 9600, in the program and in the serial monitor, I also tried with other values, no results, knowing that when I do the test with the commands (AT, AT + ATD, AT + CMGS ...) it works very well

@@TechToTinker I have two version of GSM module: SIM800L like you, and SIM800A. all the functions (call, receive a call, send a message, receive a message ...) are working very good, the only problem is the display of text message, whatever the message received it shows me these 4 characters "????".did my work on the first with 16F877 microcontroller and I didn't succeed, now I'm trying with arduino and still no result 😟😟😥 Really i need your help please, i

@@hamdiahmed5492 did you try what I said regarding changing the baud rate of your serial monitor to 9600?

@@TechToTinker of course Mr,

Hi Vivek, do mean like this? SIM800 SMS to android, SMS not receive SIM800 SMS to old phone, Ok If this is your problem, you may try: 1. Put the Sim card of SIM800 to other phone and try to send SMS to your android phone

thanks i will try this, of course i like your video..

Translation: Hello, could you help me? Both devices work separately, the arduino executes the commands if I manually put them in the serial monitor, and the SIM800L indicates that it is already connected to the network (it even links if I call the number it has), but They do not send messages, nor do the messages I send do anything, and neither does writing AT commands work, it does nothing (I have seen that when putting "AT" minimum, it must respond "OK", but no. :( I would appreciate your help -------- Hi @tcoimm, have you tried swapping your Rx and Tx?

@V V, I can't remember the capacitance of that capacitor as of now :) . Anyways, you may use any capacitor around 100 to 220uF 16V or 25V or whatever is available. Cheers.

Hi @Saad Elm, you may try to use this site to calculate Voltage divider circuit resistors. ohmslawcalculator.com/voltage-divider-calculator Vs should be 5V Vout is 3.3 Then if you have 560 Ohms for R1, you may press calculate buttons it will give 1087 Ohms. You may use 1K Ohms resistor for R2. Hope this helps you.

@Labrada, Sweet Raven, first what sensor you are going to use? Is this for flood detection alarm?

@@TechToTinker yes sir for flood detection

I used floatswitches

@@sweetravencurranlabrada4115 ok, if you will use a float switch then I believe there is no need for modification in the code.

@@TechToTinker but sir in serial monitor it is working but it wont send messages. What could be the problem

@Magboma Joshua, how do you get those error?

Hi @Mani Vannan, you may use EEPROM to do that. Please refer to this: ukposts.info/have/v-deo/gZGGZa2tgW6i0Xk.html

Thk u sir.i wil try...

Hi @Mani Vannan, if you do not yet succeeded in using EEPROM you may try this. Please be noted that this code is still subject for error because I do not test it but the concept is. //include this at the top of the code: #include "EEPROM.h" //in setup function, add this: for (i=0;i

@@TechToTinker sir I try to eeprom save on number for ur method...but only last four digit only save...pls help explain the code eeprom save

@@manivannan5098 yes Sir please help

@saroj singh, you may comment out "#define SIMULATE_BY_SERIAL" and it should work to your phone.

thanx for your kind response. I did as you suggested but the problem is still the same. plz guide me. The same gsm module working well with your other project but SMS based this one is not

Yes you can do that by replying to every sms received.

@Jayson Debelen, check the video description. It usually contains additional information.

@Jayson Debelen, comment out #define SIMULATE_BY_SERIAL Please let me know your progress.

@@TechToTinker sir ayaw po tlga sir char sender_num[14] = {'+', '6', '3', '9', '7', '5', '9', '2', '3', '1', '2', '4', '3' }; clrification po sir eto po ba sir yung number ng receiver po sir salamat po

Good pm po sir nag pm po ako sa gmail nyo na tech.to.tinker@gmail.com

@@jaysondebelen3365 yes palitan mo yan ng number mo

Hi Mark, here is the link: techtotinker.blogspot.com/2020/08/tutorial-how-to-use-sim800l-gsm-module.html. Edit: I checked and I forgot to create the circuit diagram. Anyways, you may try this for the mean time: Red led to D7 Green led to D6 Blue led to D5 Button to D4 SIM800 Rx to D12 SIM800 Tx to D11 Be sure to use limiting resistors. Thank you

Hi Mark, I just updated the blog post to include the circuit diagram. Please check it. Enjoy.

@Dhruv Patel, Im not sure what do you mean. If you mean to say that the SIM800L can't receive the message sent from your mobile, maybe you don't send the correct format of SMS. Try checking the short details at the top of the sample source code. Cheers, George Bantique | tech.to.tinker@gmail.com

@@TechToTinker I can send image on Gmail id?

Module received message but module can't send a message

How did you know that the module received the message? How did you know that it doesn't send a message? Or you may try to fully analyze your problem and give me a complete details.

@@TechToTinker when I send a message from phone it's display on series monitor so i know message was received .

Hi Jay, kindly check the video description. The links to the source should be there. Cheers.

​@@TechToTinkeramazing work sir . I have a question can I receive a readings of gauge in sms and what is the code to do that can you help me sir?

@KMV, it depends on your application. Lets say you want to call a number when a button is press so you will create a check to the button. like if (button == LOW) { // this is an active-low button, // else replaced it with == HIGH // call call_a_number() } the you will create a function like void call_a_number() { // ATD here to dial }