Technical characteristics<\/h2>\n\n
The SIM800L is a quad-band GSM<\/a> \/ GRPS<\/a> module. It covers the GSM850, EGSM900, DCS1800 and PCS1900 frequency bands. To use the SIM800L, you need a 2G micro-SIM card. Your microcontroller communicates with the SIM800L serially via RX\/TX and AT commands.<\/p>\n The voltage range for the power supply is an unusual 3.4 to 4.4 volts. For this reason and because of current peaks of up to 2 amps, power supply via the microcontroller is not possible. Lithium-ion batteries are suitable, or you can use switching regulators<\/a> such as the LM2596. For switching regulators, however, you still need a suitable power supply.<\/p>\n\n The SIM800L module has the following pins:<\/p>\n There are contradictory statements about the permissible voltage level of the serial interfaces of the SIM800L. Some say it can handle 5 volts, others see the limit at 3.3 volts. According to the data sheet<\/a>, however, the maximum is 2.8 volts. You can also find there how to optimally<\/em> connect 3.3 volt and 5 volt microcontrollers (from page 31). I only used a voltage divider in the RX line of the module and did well with it.<\/p>\n\n The SIM800L module is normally offered with one or more antennas. In many cases, you can get by with a simple spiral antenna. In areas with poor reception, interfering signals or shielded buildings, you may need a better antenna.<\/p>\n One could also come up with the idea of using two antennas. However, this can be counterproductive, as they might interfere with each other.<\/p>\n If you buy an antenna with an SMA connection (that’s the one with the screw thread), then you still need an IPX UF. L to SMA adapter.<\/p>\n\n Typical power consumption is:<\/p>\n How much power the SIM800L module consumes during a phone call or when transferring data via GRPS is not so easy to answer because the consumption is not constant. I have found quite concrete information here<\/a> (131 – 216 mA, depending on the frequency band). In my measurements I found values around 70 mA, but with peaks.<\/p>\n At the beginning of a connection, peak values of up to 2 amps can occur, as mentioned above.<\/p>\n\n The SIM card is inserted into the cardholder as shown on the right.<\/p>\n I can’t tell you which is the ideal SIM card for you. This depends too much on your application, i.e. mainly on the expected frequency of SMS or calls.<\/p>\n But I want to share an experience with you. I had bought an “IoT and M2M Prepaid” card because it sounded so beautiful. Unfortunately, the card had a “+882” country code, which stands for “International Networks”. This number is blocked by many mobile phone providers because it is also used for fraud calls. In addition, a connection with this area code can generate high costs. So calls were not easily possible, and I could only send SMS from, but not to the module. I then got another SIM card from the good old Telekom. So choose your SIM card wisely.<\/p>\n And be careful when creating programmes to send text messages so that you don’t accidentally send bulk SMS. In the best case, you have a prepaid card, which is then empty.<\/a><\/p>\n\n This is the wiring I used:<\/p>\n\n Note that RX of the module is connected to TX of the microcontroller and TX of the module to RX of the microcontroller.<\/p>\n For the above circuit, the voltage at RX of the module is:<\/a><\/p>\n<\/p>\n <\/span> <\/span> \n\n One or the other of you may already know AT commands from the HC05 \/ HC06 Bluetooth modules<\/a> or other serially controlled components. Most AT commands have this structure (exceptions prove the rule!):<\/p>\n A list of AT commands for the SIM800L module can be found here<\/a>. There are over 300 of them in this document alone.<\/p>\n The easiest way is to send the AT commands via the serial monitor of the Arduino IDE to “play around” with them. Alternatively, you can use terminal programs such as PuTTY<\/a> or HTerm<\/a>, but then you need a USB-to-TTL adapter.<\/p>\n\n Upload the following SoftwareSerial sketch to your Arduino board to communicate via the serial monitor:<\/p>\n<\/p>\n \n\n In my experience, you can work reliably with a baud rate of 9600 bps. At 115200 bps, I lost parts of SMS. In the serial monitor, you need to set the same baud rate and select “Carriage Return (CR)”.<\/p>\n\n Once you have wired everything, inserted the SIM card and supplied the SIM800L module with power, you can now start. The LED on the SIM800L module should initially light up with a frequency of about 0.8 seconds after the supply voltage is applied.<\/p>\n\n As a first test, you simply enter If everything is OK, you can now query information about the module:<\/p>\n Your SIM card may be protected by a PIN. Enter the following:<\/p>\n At the latest after entering the correct pin, the module should connect to the network and the LED should flash every 3 seconds.<\/p>\n A very useful feature is to query the battery status:<\/p>\n This means: “0<\/strong>” – battery does not charge (“1” would mean the battery charges). “75<\/strong>” means that the battery still has 75% capacity. “4005<\/strong>” stands for 4005 mV voltage.<\/p>\n You can find out the signal strength of your network as follows:<\/p>\n The first number means: <\/p>\n You can find out which network you are in as follows:<\/p>\n The essential information is behind the second comma. So here it is the D1 network. The other numbers encode mode and format. Check out the AT command list<\/a>for more information. <\/p>\n This query is also useful:<\/p>\n The second number means: “1” registered, home network; “5” registered, roaming. If you get a 2, 3 or 4, you are not registered.<\/p>\n You can find out your service provider (according to SIM card) by:<\/p>\n You activate the power-down mode with:<\/p>\n With parameter 0, the SIM800L module is switched off immediately and without feedback. Unfortunately, the power-down mode does not seem to be stable. Again and again my module switched itself on after some time. So far, I have not been able to find out the reason.<\/p>\n The sleep mode (slow clock) works better. And this is how the sleep mode is started:<\/p>\n In sleep mode, the SIM800L module is available for SMS and calls.<\/a><\/p>\n\n To send an SMS, you may have to enter your PIN and set the module to SMS text mode using You initiate the actual sending of the SMS by entering the recipient’s telephone number:<\/p>\n Then a prompt should appear ( > ). You enter the SMS text and complete the input with Ctrl+Z (ASCII code No. 26) and then press Enter. That’s the theory. Practically, I did not manage to send Ctrl+Z via the serial monitor, as it only processes visible characters. But through a sketch (see below) this is no problem. You create a Ctrl+Z with All other commands are transmitted by I have outsourced the SoftwareSerial query as a separate function (updateSerial). Since the response to an AT command can take a little time, I have added a waiting time (wt_ms = 100 ms). You may have to adjust the value.<\/p>\n The main loop allows you to enter further commands via the serial monitor. Here you do not need to wait, as you query constantly.<\/p>\n Here’s what the full sketch looks like:<\/p>\n<\/p>\n \n\n You may have noticed that the answers of the SIM800L module are read in this sketch with Here’s what the output looked like:<\/p>\n\n There are three very useful functions for evaluating and editing strings:<\/p>\n As a small example of the \n\n Why I needed the line:<\/p>\n I don’t know. Without that, it didn’t work.<\/a><\/p>\n\n To receive SMS, you must first be connected to the network again and activate the SMS text mode. In addition, you define how incoming SMS are to be handled:<\/p>\n The parameters used here ensure that the SMS text appears directly on the serial monitor.<\/p>\n<\/p>\n \n\n And this is what it looks like on the serial monitor when an SMS is received:<\/p>\n\n An alternative mode for processing SMS is: This means that SMS No. 21 has been saved in the phone memory (“ME” = Mobile Equipment). You can list the saved SMS with Instead of “ALL” you can also use “REC UNREAD” (received unread) or “REC READ” (received read) as parameters.<\/p>\n With You can control your microcontroller via SMS. I would like to demonstrate this using the example of two LEDs that I have connected to pins 9 and 10.<\/p>\n\n I called the two LEDs led1 and led2. When an SMS is received, the sketch uses the indexOf function to find out whether led1 or led2 is included in the text. Then it searches for the keyword “on”. If this is the case, led1 or led2 is switched on. If no “on” is included, the led1 or led2 is switched off. Examples:<\/p>\n \n\n Since strings are quite memory-intensive, I pass “moduleAnswer” and “smsText” as a reference (&bufString). This means that the function works with the original. Accordingly, there is no return value.<\/p>\n\n In this variant, the pin and the desired pin state (0 or 1) are directly sent in the SMS text. Examples:<\/p>\n \n\n Making calls with the SIM800L is even easier than sending SMS. Actually, you just have to make sure that your SIM800L module is connected to the net and to set up Serial\/SoftwareSerial as with the other sketches:<\/p>\n<\/p>\n \n\n You start a call with the following AT command:<\/p>\n Replace xxxxxxxxxxxx with the number to dial, starting with the country code. With Use the same sketch if you want to call your SIM800L module. The call is indicated acoustically, by “RING” in the serial monitor and by a short LOW signal at the RING pin. You could use the latter signal to wake up your microcontroller from sleep mode<\/a>. In this way, energy-saving projects can be implemented.<\/p>\n With Here are some useful functions and settings. You can query the call volume as follows:<\/p>\n And this is how you set the volume:<\/p>\n The ringtone volume is independent of this (also 0-100):<\/p>\n There are 20 ringing sounds that you set as follows:<\/p>\n I thought about how to control the microcontroller by calls. Switching on an LED is easy via “RING”. It is just as easy to turn off the LED with another call. However, it is also easy to get confused. Have I switched it on or off last time? Therefore, it would be nice to get feedback on whether the LED is on or off.<\/p>\n I managed to do that with the following sketch. When a call is received, the sketch checks the status of the LED. If it is switched on, the call will be rejected immediately. If, on the other hand, it is off, nothing happens at first. In both cases, the number of “RINGS” are counted for the next 10 seconds. If the LED was switched off, the call is rejected now. As a result, the sketch counts a different number of “RINGS” depending on the LED state. Accordingly, the LED is switched on or off. And the caller knows that if the call is rejected immediately, the LED was off and is now on.<\/p>\n<\/p>\n \n Attention:<\/strong> A rejected call is not necessarily free of charge! You might, among other things, turn off the setting that the SMS notification service is offered when “busy”. Check this before your phone bill explodes!<\/a><\/p>\n\n With the SMS and call methods, there is always a risk that someone may unintentionally or maliciously check your SIM800L without authorization. To prevent this, you can set up a whitelist. This allows you to set the phone numbers for which your SIM800L shall be reachable. The SIM800L rejects calls from devices with other phone numbers. The caller receives a busy signal.<\/p>\n Here’s how it works:<\/p>\n The mode determines whether the whitelist is effective for calls, SMS, or both:<\/p>\n The mode always applies to the entire whitelist. This means that different settings for different numbers are not possible.<\/p>\n Index is the number of the entry (1-30). “phone_number” is the phone number including the country code, but without “+” – as I found out after several hours of experimenting and researching.<\/p>\n![\"SIM800L](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2021\/11\/SIM800L_pinout-1024x589.png\")
<\/a>\n
RX \/ TX voltage level<\/h3>\n\n
Antennas for the SIM800L module<\/h3>\n
![\"Antennas](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2021\/10\/Antennen-1024x417.jpg\")
<\/a>![\"SIM800L](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2021\/10\/SIM800L_with_helical_antenna-703x1024.jpg\")
<\/a><\/figure>\n<\/div>\nPower consumption<\/h3>\n\n
\n
Notes on the SIM card<\/h3>\n
![\"How](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2021\/10\/SIM800L_Sim_Karte-741x1024.jpg\")
<\/a><\/figure>\n<\/div>\nWiring of the SIM800L module<\/h2>\n\n
![\"\"](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2021\/11\/sim800l_nano_wiring-1024x568.png\")
<\/a>![\"\[](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/ql-cache\/quicklatex.com-8e3ccd46ef6b21614fd32d94f155af1b_l3.png\" "\\"Rendered")
<\/p>\nCommunication via AT commands<\/h2>\n\n
\n
SoftwareSerial Sketch<\/h3>\n\n
#include <SoftwareSerial.h>\nSoftwareSerial mySerial(7,8);\n\nvoid setup() {\n Serial.begin(9600);\n Serial.println(\"Software Serial Sketch\");\n mySerial.begin(9600);\n}\n\nvoid loop() { \/\/ run over and over\n while(mySerial.available()) {\n Serial.write(mySerial.read());\n }\n while(Serial.available()) {\n mySerial.write(Serial.read());\n }\n}<\/pre>\nGetting Started<\/h3>\n\n
AT<\/code> and confirm with Enter or click on “Send”. The module should respond with a friendly OK<\/code>. If it does not, then check the wiring and the settings of the serial monitor again.<\/p>\nATI<\/code> \u2192 answer: SIM800 R14.18<\/code><\/p>\nAT+CPIN?<\/code> \u2192 for answer: +CPIN: READY<\/code> no PIN is necessary; for answer: +CPIN: SIM PIN<\/code> you have to enter the PIN including the quotation marks:<\/p>\nAT+CPIN=\"xxxx\"<\/code> \u2192 answer: OK<\/code> ; if the PIN is incorrect or if the PIN has already been entered: ERROR<\/code>.<\/p>\nAT+CBC<\/code> \u2192 answer: +CBC: 0,75,4005<\/code><\/p>\nAT+CSQ<\/code> \u2192 answer: +CSQ: 20,0<\/code><\/p>\n\n
AT+COPS?<\/code> \u2192 answer: +COPS: 0,0,\"D1\"<\/code><\/p>\nAT+CREG?<\/code> \u2192 answer: +CREG: 0,1<\/code><\/p>\nAT+CSPN?<\/code> \u2192 answer: +CSPN: \"Telekom.de\",0<\/code><\/p>\n\nSleep and Power Down Modes<\/h4>\n\n
AT+CPOWD=1<\/code> \u2192 answer: NORMAL POWER DOWN<\/code><\/p>\nAT+CSCLK=x<\/code> \u2192 answer: +CSCLK: x<\/code> with x = 0, 1, 2:<\/p>\n\n
AT+CSCLK=0<\/code> twice in quick succession.<\/li>\n<\/ul>\nHow to send SMS<\/h2>\n\n
AT+CMGF=1<\/code>. You may have to add a delay to give the module time to connect.<\/p>\nAT+CMGS=\"+491738xxxxxx\"<\/code><\/p>\nSerial.write(26)<\/code> . <\/p>\nSerial.println()<\/code>. Quotation marks must be preceded by a backslash so that they are not interpreted as the end of the println() statement.<\/p>\n#include <SoftwareSerial.h>\nSoftwareSerial mySerial(7,8);\nconst unsigned int wt_ms = 100; \/\/ wait ms\n\nvoid setup() {\n Serial.begin(9600);\n Serial.println(\"Send SMS Sketch\");\n mySerial.begin(9600);\n delay(1000);\n updateSerial(wt_ms);\n mySerial.println(\"AT\"); \/\/ to check if the module is connected\n updateSerial(wt_ms);\n mySerial.println(\"AT+CPIN=\\\"xxxx\\\"\"); \/\/ if Pin is needed\n updateSerial(wt_ms);\n\/\/ delay(8000); \/\/ maybe needed to setup connection to the network\n\/\/ mySerial.println(\"AT+CCID\"); \/\/ optional check\n\/\/ updateSerial(wt_ms);\n\/\/ mySerial.println(\"AT+CBC\"); \/\/ optional check\n\/\/ updateSerial(wt_ms);\n\/\/ mySerial.println(\"AT+COPS?\"); \/\/ optional check\n\/\/ updateSerial(wt_ms);\n\/\/ mySerial.println(\"AT+CSQ\"); \/\/ optional check\n\/\/ updateSerial(wt_ms);\n\/\/ mySerial.println(\"AT+CREG?\"); \/\/ optional check\n\/\/ updateSerial(wt_ms);\n mySerial.println(\"AT+CMGF=1\"); \/\/ SMS text mode\n updateSerial(wt_ms);\n mySerial.println(\"AT+CMGS=\\\"+491738xxxxxx\\\"\");\n updateSerial(wt_ms);\n mySerial.print(\"Hi Wolle, this is a message from your SIM800L Module.\"); \n updateSerial(wt_ms);\n mySerial.write(26);\n mySerial.println(\"\");\n updateSerial(wt_ms);\n}\n\nvoid loop() { \n updateSerial(0);\n}\n \nvoid updateSerial(unsigned int wait_ms){\n String dataString = \"\";\n delay(wait_ms);\n if(mySerial.available()) {\n dataString = mySerial.readString();\n Serial.println(dataString);\n }\n while(Serial.available()) {\n mySerial.write(Serial.read());\n }\n}<\/pre>\n<\/div>\nmySerial.readString()<\/code> and stored in a variable. This has the advantage that you can edit or evaluate the module’s response.<\/p>\n\nOutput to serial monitor and smartphone<\/h3>\n\n
![\"Output](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2021\/10\/sms__to__smartphone.png\")
<\/a>![\"SMS](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2021\/10\/SMS_received_on_smartphone-1024x197.png\")
Evaluating Strings<\/h3>\n\n
\n
indexOf()<\/code> \/ lastIndexOf()<\/code>: returns the next or last position of the search string within the string. If the string is not found, the functions return -1.<\/li>\nparseInt()<\/code>: searches for the next sequence of numbers in a string and returns it as an integer value.<\/li>\nsubstring(x,y)<\/code>: intersects a sequence from a string (position x to y-1).<\/li>\n<\/ul>\nsubstring()<\/code> function, I show how you specifically cut out the name of the network from the module response to a “COPS” query. In my case, the “D1″ from +COPS: 0.0,”D1”.<\/p>\n<\/p>\n#include <SoftwareSerial.h>\nSoftwareSerial mySerial(7,8);\nconst int wt_ms = 100; \/\/ wait ms\nString moduleAnswer = \"\";\n\nvoid setup() {\n String irg = \"AT+COPS\";\n Serial.begin(9600);\n Serial.println(\"Evaluate Answer\");\n mySerial.begin(9600);\n delay(1000);\n \n mySerial.println(\"AT+COPS?\");\n updateSerial(wt_ms);\n \n moduleAnswer = moduleAnswer.substring(1); \/\/ does not work without, don't know why!\n int pos1 = moduleAnswer.indexOf(\"\\\"\"); \/\/ first position of \" \n int pos2 = moduleAnswer.lastIndexOf(\"\\\"\"); \/\/ last position of \"\n moduleAnswer = moduleAnswer.substring(pos1+1,pos2);\n Serial.print(\"The module is connected to \");\n Serial.println(moduleAnswer);\n}\n\nvoid loop(){\n}\n \nvoid updateSerial(unsigned int wait_ms){\n delay(wait_ms);\n if(mySerial.available()) {\n moduleAnswer = mySerial.readString();\n }\n while(Serial.available()) {\n mySerial.write(Serial.read());\n }\n}<\/pre>\nmoduleAnswer = moduleAnswer.substring(1);<\/code><\/p>\n![\"Output](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2021\/10\/output_modify_module_answer.png\")
<\/a>How to receive SMS<\/h2>\n\n
AT+CNMI=1,2<\/code>.<\/p>\n#include <SoftwareSerial.h>\nSoftwareSerial mySerial(7,8);\nconst int wt_ms = 100; \/\/ wait ms\n\nvoid setup() {\n Serial.begin(9600);\n Serial.println(\"Receive SMS Sketch\");\n mySerial.begin(9600);\n delay(1000);\n updateSerial(wt_ms);\n mySerial.println(\"AT+CPIN=\\\"xxxx\\\"\"); \/\/ in your SIM card has a PIN\n updateSerial(wt_ms);\n mySerial.println(\"AT+CREG?\"); \/\/ optional check\n updateSerial(wt_ms);\n mySerial.println(\"AT+CMGF=1\"); \n updateSerial(wt_ms);\n mySerial.println(\"AT+CNMI=1,2\"); \/\/ defines how incoming SMS are handled\n updateSerial(wt_ms);\n}\n\nvoid loop() { \n updateSerial(0);\n}\n \nvoid updateSerial(unsigned int wait_ms){\n String bufString = \"\";\n delay(wait_ms);\n if(mySerial.available()) {\n bufString = mySerial.readString();\n }\n if(bufString != \"\"){\n Serial.println(bufString);\n }\n while(Serial.available()) {\n mySerial.write(Serial.read());\n }\n}<\/pre>\n![\"Received](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2021\/10\/Received__SMS.png\")
<\/a>AT+CNMI=2,1<\/code> (instead of “1.2”). This will ensure that the SMS are saved. You will only get a message on the serial monitor, such as:<\/p>\n+CMTI: \"ME\",21<\/code><\/p>\nAT+CMGL=\"ALL\"<\/code>:<\/p>\n\n![\"\"](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2021\/10\/List_SMS.png\")
<\/figure>\n\nAT+CMGD=21<\/code> you will delete the SMS No. 21. You can also delete all SMS at once. To do this, use the statement AT+CMGDA=\"DEL ALL\"<\/code>.<\/a><\/p>\n\nControlling the microcontroller via SMS<\/h2>\n\n
Variant 1: with indexOf()<\/h3>\n\n
\n
#include <SoftwareSerial.h>\nSoftwareSerial mySerial(7,8);\nconst int led1_pin = 9;\nconst int led2_pin = 10;\nconst int wt_ms = 100; \/\/ wait ms\n\nvoid setup() {\n String moduleAnswer = \"\";\n Serial.begin(9600);\n Serial.println(\"Control LED Sketch\");\n mySerial.begin(9600);\n pinMode(led1_pin, OUTPUT);\n pinMode(led2_pin, OUTPUT);\n \n delay(1000);\n updateSerial(wt_ms, moduleAnswer);\n mySerial.println(\"AT+CPIN=\\\"xxxx\\\"\");\n updateSerial(wt_ms, moduleAnswer);\n mySerial.println(\"AT+CREG?\"); \n updateSerial(wt_ms, moduleAnswer);\n mySerial.println(\"AT+CMGF=1\"); \n updateSerial(wt_ms, moduleAnswer);\n mySerial.println(\"AT+CNMI=1,2\");\n updateSerial(wt_ms, moduleAnswer);\n}\n\nvoid loop() { \n String smsText = \"\";\n updateSerial(0, smsText);\n \n if(smsText != \"\"){\n smsText = smsText.substring(1);\n Serial.print(\"Text: \");\n Serial.println(smsText);\n if(smsText.indexOf(\"led1\")>0){\n \n if(smsText.indexOf(\"on\")>0){\n digitalWrite(led1_pin, HIGH);\n }\n else{\n digitalWrite(led1_pin, LOW);\n }\n }\n \n if(smsText.indexOf(\"led2\")>0){\n if(smsText.indexOf(\"on\")>0){\n digitalWrite(led2_pin, HIGH);\n }\n else{\n digitalWrite(led2_pin, LOW);\n } \n } \n }\n}\n \nvoid updateSerial(unsigned int wait_ms, String &bufString){\n bufString = \"\";\n delay(wait_ms);\n if(mySerial.available()) {\n bufString = mySerial.readString();\n }\n if(bufString != \"\"){\n Serial.println(bufString);\n }\n while(Serial.available()) {\n mySerial.write(Serial.read());\n }\n}<\/pre>\n<\/div>\nVariant 2: with parseInt()<\/h3>\n\n
\n
#include <SoftwareSerial.h>\nSoftwareSerial mySerial(7,8);\nconst int led1_pin = 9;\nconst int led2_pin = 10;\nconst int wt_ms = 100; \/\/ wait ms\n\nvoid setup() {\n Serial.begin(9600);\n Serial.println(\"Control LED Sketch\");\n mySerial.begin(9600);\n pinMode(led1_pin, OUTPUT);\n pinMode(led2_pin, OUTPUT);\n \n delay(1000);\n updateSerial(wt_ms);\n mySerial.println(\"AT+CPIN=\\\"xxxx\\\"\");\n updateSerial(wt_ms);\n mySerial.println(\"AT+CREG?\"); \n updateSerial(wt_ms);\n mySerial.println(\"AT+CMGF=1\"); \n updateSerial(wt_ms);\n mySerial.println(\"AT+CNMI=1,2\");\n updateSerial(wt_ms);\n}\n\nvoid loop() { \n waitForSMS();\n}\n \nvoid waitForSMS(){\n int led = 0;\n bool state = false;\n if(mySerial.available()){\n while(((char)mySerial.read())!= '\\n'){}\n led = mySerial.parseInt();\n state = mySerial.parseInt();\n digitalWrite(led, state);\n }\n}\n\n\nvoid updateSerial(unsigned int wait_ms){\n String bufString = \"\";\n delay(wait_ms);\n if(mySerial.available()) {\n bufString = mySerial.readString();\n }\n if(bufString != \"\"){\n Serial.println(bufString);\n }\n while(Serial.available()) {\n mySerial.write(Serial.read());\n }\n}<\/pre>\n<\/div>\nMaking calls<\/h2>\n\n
#include <SoftwareSerial.h>\nSoftwareSerial mySerial(7,8);\nconst int wt_ms = 100; \/\/ wait ms \n\nvoid setup() {\n Serial.begin(9600);\n mySerial.begin(9600);\n Serial.println(\"Call or wait for a call\");\n delay(1000);\n mySerial.println(\"AT\"); \/\/ optional check\n updateSerial(wt_ms);\n mySerial.println(\"AT+CPIN=\\\"++++\\\"\");\n updateSerial(wt_ms);\n mySerial.println(\"AT+CREG?\"); \/\/ optional check\n updateSerial(wt_ms);\n}\nvoid loop() { \n updateSerial(0);\n}\n \nvoid updateSerial(unsigned int wait_ms){\n String dataString = \"\";\n delay(wait_ms);\n if(mySerial.available()) {\n dataString = mySerial.readString();\n if(dataString != \"\"){\n Serial.println(dataString);\n }\n }\n while(Serial.available()) {\n mySerial.write(Serial.read());\n }\n}<\/pre>\nOutgoing call<\/h3>\n\n
ATD+ +xxxxxxxxxxxx;<\/code><\/p>\nATH<\/code> you end the call. Don’t forget the semicolon at the end (it’s no spelling mistake!). <\/p>\n\nIncoming call<\/h3>\n\n
ATA<\/code> you take the call, with ATH<\/code> you reject it.<\/p>\n\n![\"Incoming](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2021\/10\/incoming_call.png\")
<\/a>Telephony settings <\/h3>\n\n
AT+CLVL?<\/code> \u2192 answer: +CLVL: 33<\/code><\/p>\nAT+CLVL=x<\/code> with x = 0 – 100<\/p>\nAT+CRSL?<\/code> (Query) \/ AT+CRSL=x<\/code> (Setting)<\/p>\nAT+CALS=x<\/code> with x = 0 – 19<\/a><\/p>\n\nControlling the microcontroller by call<\/h2>\n\n
#include <SoftwareSerial.h>\nSoftwareSerial mySerial(7,8);\nconst int ledPin = 9;\nconst int wt_ms = 100; \/\/ wait ms\n\nvoid setup() {\n String moduleAnswer = \"\";\n Serial.begin(9600);\n Serial.println(\"Control LED by Call\");\n mySerial.begin(9600);\n pinMode(ledPin, OUTPUT);\n delay(1000);\n updateSerial(wt_ms, moduleAnswer); \n mySerial.println(\"AT+CPIN=\\\"xxxx\\\"\"); \/\/ in case a PIN is required\n updateSerial(wt_ms, moduleAnswer); \n mySerial.println(\"AT+CREG?\"); \/\/ optional check\n updateSerial(wt_ms, moduleAnswer);\n}\n\nvoid loop() { \n String ring = \"\";\n int noOfRings = 0;\n unsigned long callTime = 0;\n const unsigned long threshold = 10000; \n \n updateSerial(0, ring); \n \n if(ring != \"\"){\n if(ring.indexOf(\"RING\")>0){\n noOfRings++;\n callTime = millis();\n ring = \"\";\n if(digitalRead(ledPin)){\n mySerial.println(\"ATH\");\n }\n \n while((millis()-callTime)<threshold){\n updateSerial(0, ring); \n if(ring != \"\"){\n if(ring.indexOf(\"RING\")>0){\n noOfRings++;\n ring = \"\";\n }\n }\n }\n if(noOfRings == 1){\n digitalWrite(ledPin, LOW);\n }\n else{\n digitalWrite(ledPin, HIGH);\n mySerial.println(\"ATH\");\n }\n }\n }\n}\n \nvoid updateSerial(unsigned int wait_ms, String &bufString){\n bufString = \"\";\n delay(wait_ms);\n if(mySerial.available()) {\n bufString = mySerial.readString();\n }\n if(bufString != \"\"){\n Serial.println(bufString);\n }\n while(Serial.available()) {\n mySerial.write(Serial.read());\n }\n}<\/pre>\n<\/div>\nRestrict the access – Whitelist<\/h2>\n\n
AT+CWHITELIST=mode,index,phone_number<\/code><\/p>\n\n