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UNIVERSAL GSM SHIELD – The GSM library for Arduino

UNIVERSAL GSM SHIELD – The GSM library for Arduino


Let’s discover a useful library to handle numerous low-cost GSM/GPRS modules, so as to provide mobile connectivity to our Arduino tasks. Second half.

Within the earlier episode, we introduced the defend hardware and exposed the technical features and attainable purposes, in addition to talked about the library for Arduino, here we complete the earlier speech explaining intimately its operation, which supports the boards Arduino Uno, Arduino Mega 2560, Fishino Uno and Fishino Mega 2560. The library is composed of the primary file plus the secondary information containing the code essential to handle a collection of features that send AT commands to the GSM module put in within the defend. The primary file is GenericCmd_GSM.cpp and accommodates the infrastructure code that retains the features within the different library information interconnected. With a collection of directives, it’s attainable to activate/deactivate elements of the code in addition to choose the specified Arduino board and the corresponding GSM module to be related.

The modules presently supported by the library are:
– SIM900 (SIMCOM);
– G510 (FIBOCOM);
– M95 (QUECTEL).

We need to remind you that the SIM928A supplies for the administration of two serial numbers. For all the modules solely the SMS and voice call management features are presently supported, whereas the GPRS management features for Internet connection and knowledge sending/receiving are underneath improvement. In the future, the management a part of the GPS system may also be developed.
To raised perceive a number of the terms used under, you need to keep in mind that GSM modules could be outlined as:
• ME (Cellular Gear);
• MS (Cellular Station);
• MT (Cellular Termination);
• TA (Terminal Adapter);
• DCE (Knowledge Communication Gear).

The units that management the GSM modules, by sending applicable AT commands, could be:
• TE (Terminal Gear);
• DTE (Knowledge Terminal Gear), a time period equivalent to the appliance that runs on an embedded system and is liable for the GSM module management.



The library is designed for sending an AT command by way of a particular perform and waiting for the response from the GSM module. This is made attainable by a collection of state machines that take cost of each the sending of the AT command and the management of the response by the module. At present, some widespread AT commands have been selected and carried out in the library.
To make use of it you have to copy all the information that may be downloaded from the location within the folder “C:Program Information (x86)Arduinolibraries/GSM2”. As soon as all information have been copied, the library have to be initialized by the consumer relying on the hardware used and the GSM module selected. Particular features have additionally been developed to activate the method of GSM module initialization (module energy on, and sending AT configuration instructions) which is absolutely automated, together with the request for the PIN code (if required) and sending it to the GSM module. Notice that the PIN codes, PUK and so forth. are stored in the Arduino EEPROM, subsequently, contemplating how an Arduino system is structured, it’ll take a special sketch to load the info into the EEPROM. The present Arduino IDE, unfortunately, does not permit EEPROM programming through the challenge compilation.
Wanting at the associated file “GenericCmd_GSM.h” (which may be opened with a text editor like Notepad++) we find within the head a collection of constants, all stored in FLASH by means of the “PROGMEM” directive, which determine a collection of AT commands used each for initialization of the GSM module and for widespread use within a sketch. The AT commands used in the library are all the time stored in flash in order to not occupy SRAM reminiscence unnecessarily. Actually, if we had used the strategy of defining a string for each AT command to send, we might not have had enough SRAM reminiscence to develop the library and its sketches. (Fig. 1)
Underneath the stored AT commands, there is a collection of directives that determine the constants used in the management of the relative AT commands. The ASCII character codes and STEP codes of the state machines used to ship AT instructions throughout both initialization and full operation are additionally defined. Lastly, we’ve defined a collection of error codes which will return from the GSM module, specifically the CME and CMS error codes.
On the finish of all of the directives described, we find the declarations of the variables used and their features, whether or not they are public or personal.
The file just described is combined with an equally essential one, “Io_GSM.h”, which incorporates the declarations for the defend hardware configuration, plus the likelihood to allow/disable the varied state machines or the extra debug code.


Fig. 1

The first thing you notice when opening the file is the presence of a table (through which are highlighted the attainable mixtures that may be obtained with the jumpers on the board (corresponds to Table 1 that you simply discover in the first episode). Relying on how they are positioned, you possibly can choose, for instance, which communication interface to use, i.e. hardware or software UART with or and not using a serial mild. Direct communication with the PC can also be potential, bypassing Arduino.
Afterward, the rules for choosing the GSM module for use (among these supported) start; only one may be set at a time. To pick the module, you must uncomment the corresponding line without altering the others:

#outline SIMCOM_SIM800C // Use this for SIMCOM SIM800C GSM module
//#define SIMCOM_SIM900 // Use this for SIMCOM SIM900 GSM module
//#outline SIMCOM_SIM928A // Use this for SIMCOM SIM928A GSM module
//#define FIBOCOM_G510 // Use this for FIBOCOM G510 GSM module
//#define QUECTEL_M95 // Use this for QUECTEL M95 GSM module

The bolded line identifies the GSM module you need to use, while the others correspond to the supported however not chosen modules. This concept applies to all attainable choices of a single object from an inventory of alternatives.
The next are the guidelines for selecting the Arduino board to be used: Arduino Uno or ArduinoMega 2560 (FishinoUno and FishinoMega 2560).
The next is the number of the hardware revision; improvement started with version, which clearly lost its which means. At present, only version R.1.2 ought to be selected.
Upon getting defined the hardware, you must inform the compiler whether to make use of the hardware or software program UART interface; the second obtainable UART, both hardware and software, just isn’t used however stays obtainable for future developments.
Ultimately, we have now to assign a singular identify to the Arduino pins, whose first half considerations the hardware revision (which is obsolete), whereas instantly after we discover the definitions relating to the hardware revision 1.2:
• Pin definition for Arduino Uno utilizing the “ARDUINO_UNO_REV3” directives;
• Arduino Mega 2560 pin definition utilizing the “ARDUINO_MEGA2560_REV3” directive.

Let us keep in mind that just one directive might be chosen. In the pin record definitions, we find the UARTs’ TX and RX alerts, both software and hardware, the definition of the LEDs related to the Arduino, in addition to the trigger alerts.
As soon as the configuration of the hardware half has been accomplished, it’s mandatory to modify to the activation or deactivation of some software sections for the management of the responses acquired from the GSM module to the AT commands despatched. As traditional, directives are used. On this case, it is attainable to have a number of sections enabled on the similar time. At present we have now 5 potential state machines, which have an effect on:
• responses to generic AT instructions, such because the AT+CFUN command;
• responses to AT commands for security administration, such because the AT+CPIN command;
• solutions to AT instructions to manage the telephone guide, such because the AT+CPBS command;
• responses to AT instructions for SMS administration, comparable to AT+CMGD;
• Solutions to AT commands for dealing with voice calls, such as the ATA command.

So, we’ve the next defines:


For each state machine there’s a distinctive identification code needed for the right management of responses; codes and definitions go hand in hand, so if you create new sections of code to handle responses to AT commands you will have to both add a definition for activating/deactivating the code, or assign a singular code to the brand new part. Under are the codes already assigned within the library:


The final section incorporates debugging directives, which allow/disable code sections inside the library for debugging despatched AT commands and their responses, knowledge stream on the chosen serial, ON/OFF/RESET of the related GSM module and management of AT security commands.
The debug info is printed on the Arduino IDE serial monitor utilizing the default serial connection so, out of your code, you need to allow the serial debug at the desired velocity and set the serial monitor accordingly.


Having stated that, we now have the global directive “DEBUG_MODE” which has the perform of MASTER and if commented, it disables your complete debug code in the library. A collection of SLAVE directives comply with to pick what you obviously need to debug with the lively MASTER directive. Hence, we’ve got the next directives:
• “UART_DEBUG” to examine the serial connection standing, that’s:
– Idle = ready to do one thing;
– Send = sending knowledge in progress;
– Wait = ready for a response from the GSM module;
– Overflow = Overflow detected;
• “GSM_CMD_DEBUG_AT_CMD” for the analysis of knowledge despatched to the GSM module and related responses (the debug mode additionally intercepts strings acquired autonomously from the module);
• “GSM_CMD_DEBUG_ON_OFF” for the analysis of the actions of energy ON, power OFF and RESET of the GSM module;
• “GSM_SECURITY_DEBUG” for the analysis of the PIN and PUK management features of the SIM card.

For each of the listed directives, there are code sections scattered all through the library; every one is associated with the extra text to determine/understand what is being displayed on the serial monitor.
All debugging text is saved within the microcontroller’s FLASH memory to save lots of useful SRAM memory. Keep in mind also that getting into the debug code occupies a sure memory area in the FLASH which have to be taken under consideration, particularly should you use Arduino Uno.
On the file finish, we find variable and performance declarations; in this case, there are solely:
• a perform for the configuration of the Arduino I/O for the management of the LEDs (hardware 1.2 and Arduino Mega 2560 (void SetOutputLed(void) required); it may be recalled from any sketch and isn’t required to move parameters to it;
• a perform for the configuration of Arduino I/O for the administration of triggers (void SetOutputTrigger(void)); it may be recalled from any sketch and it isn’t required to cross parameters to it;
• a perform to verify the LEDs related to the Arduino, for use as a check throughout initialization; hardware 1.2 and Arduino Mega 2560 (void CheckOutputLed(void)) are required; the perform might be recalled from any sketch and is not required to cross parameters to it;
• a perform to verify triggers related to Arduino, to be used as a check throughout initialization (void CheckOutputTrigger(void)); the perform might be referred to as from any sketch and isn’t required to move parameters to it;
• a perform to turn on the LED related to the Arduino; hardware 1.2 and Arduino Mega 2560 are required (void LedOn(uint8_t LedSelected)); it can be recalled from any sketch however requires as parameter the number of I/Os to which the LED is related (e.g. PIN_LED4 );
• a perform to modify off the LED related to the Arduino; hardware 1.2 and Arduino Mega 2560 are required (void LedOff(uint8_t LedSelected)); the perform may be recalled from any sketch and requires as parameter the variety of I/Os to which the LED is related (for instance PIN_LED4);

These are followed by two features for the triggers management (void TriggerOn(uint8_t TriggerSelected) and void TriggerOff(uint8_t TriggerSelected)); each may be recalled from any sketch and require as parameter the variety of I/Os to which the trigger is related: for example TRIGGER_1 .
Finally, a perform has been outlined for flashing an LED amongst these related to the I/O of the Arduino board (void LedBlink(uint8_t LedSelected, uint8_t DutyCycle, uint8_t TimeOutConstant)); the perform may be recalled from any sketch and requires three parameters:
– I/O to which the LED is related (e.g. PIN_LED4);
– duty-cycle flashing (e.g. 50%);
– the time constant, similar to the period of the sq. wave that drives the LED (for instance 250ms corresponds to T_250MSEC.

The features described above can then be referred to as up within the sketches with a purpose to have feedback of conditions, such because the reception / sending of an SMS, the reception of a voice call, and so forth. E.g., let’s suppose that through the initialization part we decided to use the flashing perform to indicate that the GSM module is being initialized, the LED will stop flashing only after initialization is complete. The flashing perform applies to both LEDs and triggers.
After this preamble, we go back to the file “GenericCmd_GSM.cpp” and analyze the way it works to send a generic AT command, so we won’t cope with the initialization for now, or any decoding of the GSM module response.
We analyze the sending of the command AT+CFUN, which requires a parameter that units the level of performance of the GSM module that is:
• 0 = minimal performance;
• 1 = full functionality;
• 4 = RF transmission and reception levels disability.

The perform is said as uint8_t GenericCmd_GSM::SetCmd_AT_CFUN(uint8_t FUN_Code) and has as parameter the code to cross to the thought-about AT command; it returns zero if it didn’t send the required AT command and 1 if the command was despatched efficiently.
Before sending the AT command the perform:
• resets the info transmission/receipt buffer to zero;
• saves the acquired parameters in case it tries to ship the AT command once more in case of problems (it tries to send the command for a maximum of 3 times);
• sets a flag that identifies that the AT command sending course of is beginning;
• resets all other administration flags.

As soon as this is finished, the perform is able to compose the AT command to be despatched after which reads from FLASH the AT command to be despatched, in this case, AT+CFUN. Keep in mind that all AT instructions used are stored within the FLASH, for many who need parameters, these can be added on the finish of the command. Reading the AT command from FLASH, the system adds the required parameter within the queue and updates a variable containing the length of the AT command to be despatched (keep in mind that the AT command is a string). This variable is utilized by the serial management perform to know when it has completed sending all the bytes (chars) that make up the command.
Lastly, it calls up a perform for initialization of the machine in states for sending the command itself:

This perform units the IDLE status for this commands’ category, the wait status for the GSM module to wait for the response and, lastly, the class to which the command belongs, which on this case is a part of the generic ones. A typical AT command sending perform is completed as in Itemizing 1.
How does the system start sending the AT command? To do that, a special perform void Uart_GSM::ExecuteUartState (void) has been arrange, which is constantly referred to as in the void loop cycle of the sketch (Gsm.ExecuteUartState()). In this perform, we’ve got a state machine, made with a change assemble, which is all the time in IDLE mode until it notices that the flag UartFlag.Bit.SendData has not gone to 1 and the variable containing the length of the AT command to be sent is bigger than 0. When these two circumstances are verified the system goes into the state of sending command or UART_SENDDATA_STATE. As soon as this new state is executed, the info in the transmission buffer is shipped to the lively serial on the set velocity, the system then sets a new state of ready for the response from the GSM module or UART_WAITDATA_STATE. On this new state, the system waits for a response from the GSM module; the status is finished if there isn’t a extra knowledge out there for reception or if a reception time-out expires. Once reception is complete, the IDLE status is about once more. Fig. 2 exhibits the operation of the state-controlled machines for sending/receiving serial knowledge. Inside the features that make up the UART communication management standing machine, we discover the presence of conditional code that is activated and compiled only if the directives mentioned above are lively, resembling those to activate the serial debug code. Presently, only UART1 is used and in addition for this there are tips for activating and compiling the required code when using UART1 hardware or software.


Fig. 2

Another elementary perform for the administration of responses by the GSM module to AT commands despatched is the following:


This perform is constantly recalled within the void loop() cycle of the sketch. It aims to name up the fitting perform to decode the replies acquired from the GSM module. There are, in the intervening time, seven attainable instances related to the totally different classes of AT instructions into which we now have divided the library. For each of them, a directive has been outlined to activate the corresponding code after which make it obtainable to the compiler.
The perform that deals with decoding the response acquired from the GSM module to the command despatched earlier than (AT+CFUN) are:


The perform performs a collection of exams as a way to ensure that it’s attainable to start out decoding the info acquired concerning the command sent and that subsequently there are nonetheless no slopes to be completed. Then you definitely ensure that there’s knowledge within the buffer by operating a check on the variable ReadPointer which indicates what number of bytes have been acquired from the serial port.
The value have to be higher than zero for the perform to begin decoding the response.
The second check checks that inside the acquired string there’s the phrase “OK” which signifies that the AT command has been acquired, understood and executed. Relying on the command despatched, there could also be only the wording “OK” or perhaps a collection of parameters in response to the request made. For instance, if the AT command sent had been AT+CREG? the response acquired would have contained not only the wording “OK” but in addition the following potential string: +CREG: 2,1,”0065″,”16F3″.
Having stated this, the code, once verified that within the string there’s the phrase “OK”, proceeds with the next decoding of what has been acquired using the assemble change to which you need to move the code of the AT command despatched.
Every AT command is coded with a singular code as talked about above. Within the case of the AT+CFUN command, the system doesn’t carry out some other operation as there are not any parameters to be decoded within the response.
If the command despatched had been AT+CREG? the system would have decoded the info present within the response and saved in a special knowledge construction referred to as CREG_Info. One of many info that is extrapolated from the response is the connection status, which is saved in the variable CREG_Info.Stat.
The connection status might be:

• “0” = not registered;
• “1” = recorded;
• “2” = on the lookout for an operator to register for;
• “three” = registration denied;
• “4” = unknown;
• “5” = registered as roaming.

Other two extrapolated info are the “location space code” or extra merely “lac” and the “Cell ID” or more simply “ci”; this info is saved in the two variables CREG_Info.LAC_Info and CREG_Info.CI_Info.
There are two different primary features: the primary “listens” on the serial port and if unbiased knowledge packets arrive from the AT commands despatched, it intercepts and sends them to the reception buffer (Gsm.UartContinuouslyRead(); ). This knowledge is known as “Unsolicited End result Code” and is info that the GSM module routinely sends because of occasions occurring on the GSM community, reminiscent of a cell change, a disconnection, and so forth.
The second perform (Gsm.ProcessUnsolicitedCode(); ), then again, decodes the info acquired from the earlier perform; it’s presently capable of decode the “Unsolicited End result Code” regarding SMS, voice calls and the connection state to the cell.
So we will summarize that the code needed in the void loop() loop of the sketch is as follows:

if (Gsm.GsmFlag.Bit.GsmInitInProgress == 1)

As you possibly can see, we discover the features we’ve got described before; the construct “if else” is used to know if the system is initializing the GSM module; on this case solely the following features can be referred to as:


The primary sends the AT initialization command, the second waits for and decodes the response from the GSM module.

We just have to explain the GSM module initialization process: the initialization cycle begins from the void setup() of the sketch, calling the perform Gsm.InitPowerON_GSM() which configures the machine to states of sending instructions initialization and the machine to states of sending steady commands, the latter is put in IDLE mode till the top of the initialization.
The first step is the facility on of the GSM module by the use of a particular impulse, which is followed by the waiting for a response; it’s because when the GSM module is switched on it all the time responds, until otherwise programmed, with a string indicating that the facility on was successful. They often reply with a string like “RDY”, SIMCOM and QUECTEL modules, or with “AT command ready” for FIBOCOM. If the module responds like this, it signifies that the ignition has been profitable and which you could move on to the subsequent step, otherwise the next might have occurred:
• the GSM module was already on and subsequently was turned off; this is clear why the module sent the string “NORMAL POWER DOWN”; (this is applicable to SIMCOM and QUECTEL) and on this case the system re-proposes the facility on command;
• If you don’t receive any response, it might be because the GSM module is either off (FIBOCOM) or needs to synchronize the velocity of the serial by way of autobaud and then it’s essential to send the command AT until the synchronization takes place;

In each instances, the system is ready to react. Once the GSM module has been switched on, the system sends a collection of AT initialization instructions, adopted by the sequence of instructions despatched:
• AT&F0 = Returns parameters to manufacturing unit values;
• ATE0 = disables “Echo mode”;
• ATQ0 = units the system to receive the “end result code” from the GSM module; for instance the code “OK” after sending a successful command or “ERROR” for a improper or not understood command (we advocate to have this perform lively);
• ATV1 = sets the format of the reply sent by the GSM module; in our case we set the “verbose code” (utilized in our library) with a view to receive text strings and never easy numeric codes (for instance “OK”, “CONNECT”, “ERROR”, “BUSY”);
• AT+CMEE = sets the format that should have the error codes reported by the GSM module, during which case our library is about to obtain error codes in numerical format only, which can be decoded by the library (you possibly can disable this perform, but isn’t beneficial, or set it to obtain errors in “verbose “);
• AT+IPR = the serial velocity is not fastened at 57600 but the autobaud is about;
• AT+ICF = sets serial communication with Eight knowledge bits, zero parity bits and 1 stop bit;
• AT+IFC = disables knowledge movement control;
• AT+CPIN? = verify if it’s essential enter the PIN code to unlock the SIM card;
• AT+SPIC = if the SIM requires the PIN code, the system checks what number of attempts are still left earlier than sending it, since sending the fallacious PIN 3 times disables its operation until you enter the PUK code; if less than two attempts stay, it does not ship the PIN;
• AT+CPIN = sends to the SIM the PIN stored within the microcontroller EEPROM; if the PIN despatched to the SIM is incorrect, the GSM module returns the error code 16 and the initialization algorithm intercepts this anomaly, interrupting the initialization itself;
• AT+CLVL = sets the quantity of the spk output;
• AT+CMIC = sets the microphone enter achieve;
• AT+CRC = allows the CRC (Cellular End result Code) parameter within the extended format, so once you receive a voice name the GSM module will send the code “+CRING: VOICE” as an alternative of the string “RING”;
• AT+CLIP = allows the Calling Line Id (CLI) parameter so that in an incoming voice name the caller’s telephone quantity is displayed, which is beneficial in purposes with telephone quantity discrimination;
• AT+CMGF = units the SMS format; the library makes use of the Text Mode format and does not help the PDU mode;
• AT+CSCS = sets the character set “IRA” or International Reference Alphabet;
• AT+CNMI = units how, via an unsolicited outcome code, the receipt of an SMS by ME have to be indicated; in our case:
– is about to 1, so if the communication hyperlink is busy the unsolicited outcome code might be discarded and never despatched, otherwise, it is going to be immediately sent to the TE;
– is about to 1, so once you obtain an SMS it is saved in the designated reminiscence area, see AT+CPMS command, so the unsolicited outcome code sent may even include the reminiscence info used to store the SMS;
– is about to “zero”;
– is about to “0”;
– is about to “0”.
• AT+CPMS = units the memory areas by which despatched and acquired SMS are to be saved; the library works with “SM” memory (SIM message storage);
• AT+CSMP = sets the validity interval of the SMS sent or stored in the reminiscence areas;
• AT+CREG = allows community registration and the power to retrieve information about the cell you’re related to both by way of unsolicited end result code or by means of direct reading.



Keep in mind that when the AT+SPIC command is executed, if the number of makes an attempt obtainable to send the PIN code is lower than 2, the method is interrupted, as a result of there are not any automatisms for sending the PUK code; this have to be entered manually, for example utilizing the serial connection to the PC or using a cell phone.
When initialization is full, the system resets the flag indicating initialization in progress (Gsm.GsmFlag.Bit.GsmInitInProgress), thus enabling the system to ship AT instructions to manage its software.
When an AT command is shipped to the GSM module, each during initialization and when sending a generic AT command, there is a risk that this will not be understood by the module. On the idea of the response acquired or not acquired by the GSM module, it retries up to a maximum of 3 times the sending of the AT command; if after the three makes an attempt to ship the command just isn’t acquired then the system will reset the module itself and this includes the GSM module re-initialization.
If the GSM module returns error codes these will probably be decoded by the perform:

For each of the error codes managed there’s a corresponding flag to indicate the detection, it’s going to then be the consumer’s duty to handle the flags in a consistent-with-their-application method.
There are at present four classes of identifiable error codes:
• Common: to be discovered beneath Gsm.GsmFlag or underneath Gsm.SimFlag;
• Safety: discovered beneath Security.SecurityFlag;
• Calendar: may be found underneath PhoneBook.PhoneBookFlag;
• Messages: could be discovered underneath Sms.SmsFlag.

The file “GenericCmd_GSM.cpp” in addition to the initialization section has a lot of features for sending a collection of AT instructions chosen with the intention of facilitating the event of purposes “GSM oriented”. In the intervening time we do not cover all attainable conditions however with time we expect we will reach an excellent compromise between carried out features and needed management code, especially for decoding the responses acquired by the GSM module. Among the many options at present supported by the file “GenericCmd_GSM.cpp”, we’ve got:
• Generic AT command, the perform have to be handed the size of the command string as a parameter. It is nonetheless underneath improvement, particularly with regard to response administration (Gsm.SetCmd(uint8_t Lenght)).
• AT command to modify off GSM module by way of software, which differs between SimCom, Quectel or FIBOCOM; in the case of Quectel additionally needs a parameter that if “0” signifies that you must do an urgent power down and then as a response to the command is shipped solely “OK”, while if “1” signifies that you must do a traditional power down after which as a response you receive the string “NORMAL POWER DOWN” (Gsm.SetCmd_SwPowerDown(uint8_t Sort)).
• Command to modify off GSM module from hardware (by a pulse of applicable period) or Gsm.SetCmd_SetCmd_HwPowerDown(void); ).
• AT command for perform setting (Gsm.SetCmd_AT_CFUN(uint8_t FUN_Code)).
• AT command for studying or setting the date and time; it has a Boolean parameter to indicate in case you are reading the date and time or in case you are setting it. If “true” it reads if “false” it writes. The date and time are formatted in a string for each studying and writing. The formatting of the string is “yy/MM/dd,hh:mm:ss±zz” i.e. yr, month, day, hours, minutes, seconds and the time zone that can vary from -48 to +48. The time zone signifies the difference, expressed in quarters of an hour, between the time and the native date with respect to the GMT. Time zones are defined in relation to GMT, with a constructive integer if late or a unfavorable integer if early (Gsm.SetCmd_AT_CCLK(bool Question)). The library has a knowledge structure that, because of a 64bit “union”, permits you to set or learn the date and time values and consists as follows:


Then the consumer in case of date and time setting should first fill in the fields of the info construction after which name the perform Gsm.SetCmd_AT_CCLK(bool Question). However, in case you perform a reading, you will see these fields crammed in with the info learn by the GSM module.
• AT command to learn the manufacturer code: it exists in two codecs between which the command string varies depending on the version V25 or 3GPP, and subsequently wants a parameter to determine which format to use: “zero” format V25, “1” format 3GPP. In the corresponding .h file are outlined the constants for this kind of command (Gsm.SetCmd_ATQ_GMI(uint8_t FormatAt)). The read knowledge is saved utilizing the info construction ME_Info
• AT command to learn the model code of the GSM module. The issues made for the command model you need to use apply (Gsm.SetCmd_ATQ_GMM(uint8_t FormatAt)).
• AT command to read the software program revision loaded in the GSM module. The issues made for the command version to be used (Gsm.SetCmd_ATQ_GMR(uint8_t FormatAt)) apply.
• AT command to read the IMEI code (serial identification quantity). The issues made for the command model to be used (Gsm.SetCmd_ATQ_GSN(uint8_t FormatAt)) apply.
• AT command to learn the knowledge in regards to the registration of the GSM module to the community (Gsm.SetCmd_ATQ_CREG(volid)). The AT command receives up to three parameters as a response:
– = exhibits the code with which the command has been configured or “0” indicates that you’ve disabled the registration to the community, “1” that you’ve enabled the registration to the network and activated the unsolicited outcome code relating to the connection standing and eventually “2” that is enabled the registration to the network and activated the unsolicited end result code relating to the connection status and the situation info and ; through the initialization of the module is shipped the command AT+CREG=2 so as to have all the potential info on the status of registration to the GSM network;
– = signifies the status of the recording to the GSM community. Potential values are: “zero” not registered on the community and no different operator search, “1” registered on the GSM community with its personal operator, “three” not registered, “4” unknown and eventually “5” registered on the community but roaming;
– = hexadecimal code in string format that identifies the situation;
– = hexadecimal code in string format that identifies the code of the cell to which you’re related.
This info is made out there by the CREG_Info knowledge construction which additionally, because of a “union”, allows us to group extra info together and make it obtainable in a simple approach to the consumer.
• AT command to read the GSM sign power (Gsm.SetCmd_ATQ_CSQ(volid)) which answers with the next two parameters:
– = if it returns values like “0” and “1” it signifies that the GSM signal could be very weak or absent. Values between “2” and “30” show a weak to the great signal state of affairs. If, however, it reviews a worth of “31”, it signifies that the signal is excellent. If it returns “99” it identifies an unknown or unmeasurable condition. Destructive values in dBm are related to the above numbers, the place less than -101dBm means very weak sign, values between -100dBm and -91dBm determine the weak sign, while between -91dBm and -81dBm the sign is medium and from -80dBm up the signal is sweet or excellent.
– = this parameter identifies a proportion value between “0” and “7” and is known as “bit error score”. If it returns the value “99” it identifies an unknown or unmeasurable situation. This info is recorded within the CSQ_Info knowledge construction accessible to the consumer.
• AT command to read the identify of the operator who answers with the next two parameters:
– = signifies the working mode. Then “0” automated mode, “1” guide mode, “2” guide de-recording from the community, “3” units only the parameter and eventually “Four” automated and guide mode lively. If the guide mode fails, the automatic mode is activated routinely:
– = this parameter units the format that the sector ought to have. Then if “zero” alphanumeric format lengthy as much as a most of 16 characters, if “1” brief alphanumeric format and eventually if “2” numeric format;
= this parameter exhibits the operator you’re related to.
The acquired info is saved within the SimFlag knowledge construction, particularly underneath the headings OperatorSelMode and OperatorSelFormat, while the identify of the operator is saved in the OperatorName array.
• AT command to verify the standing of the GSM module; in other phrases, it is used to see if it is busy making a voice name or different. This may be useful earlier than sending sure AT instructions (Gsm.SetCmd_ATQ_CPAS(volid)). The reply is a parameter referred to as that can assume the following numerical values: “zero” able to obtain any AT command, “2” unknown state (it isn’t stated that the GSM module (ME) responds to a attainable command), “3” lively ringing (somebody is looking or has acquired an SMS) and eventually “Four” voice name in progress. The above values are saved in the SimFlag knowledge structure and particularly beneath the heading PhoneActivityStatus.
• AT command to set the speaker quantity degree, the command requires a parameter that signifies the quantity degree you need to set. The permitted values vary from 0 to 100 for SimCom and Quectel models and from zero to six for FIBOCOM. Throughout initialization, the values are set to 90 for SimCom and Quectel fashions and 6 for FIBOCOM. (Gsm.SetCmd_AT_CLVL(uint8_t FormatAt))
• Lastly, we now have an AT command to set the achieve degree of the microphone related to the GSM module. The command requires two parameters: the channel and the achieve degree, this for the SimCom and Quectel modules. As an alternative, FIBOCOM has only the achieve degree. So, we now have that:
– : This parameter (SIMCOM) can assume the values: “0” essential audio channel, “1” auxiliary audio channel, “2” foremost audio channel in “hand free” mode and “three” auxiliary audio channel in “hand free” mode. For Quectel the potential values are “zero” regular microphone, “1” headset microphone and “2” speaker microphone. As far as FIBOCOM is worried, this parameter loses its which means
– : This parameter signifies the microphone achieve degree and for all three GSM module households the potential values range from 0 to 15.
The perform to make use of is subsequently Gsm.SetCmd_AT_CMIC(uint8_t Channel, uint8_t GainLevel)).




We have now subsequently coated the AT instructions out there in the file “GenericCmd_GSM.cpp” and we at the moment are prepared to move on and analyze the other library information, beginning with “SmsCmd_GSM.cpp” for the SMS management.
• AT command to pick the place to retailer the SMS: it can be used both to learn the current configuration and to set the three memory areas; within the latter case, it requires three parameters. The perform that calls this command additionally needs the fourth parameter to differentiate if you want to read the configuration fairly than write parameters (Sms.SetCmd_AT_CPMS(uint8_t TypeOfMem1, uint8_t TypeOfMem2, uint8_t TypeOfMem3, bool Question)). So we have now:
– = reminiscence area 1, which is used for reading or deleting SMS messages (the three areas are SIM resident, GSM/GPRS resident and indicating all memory areas associated with a GSM/GPRS gadget, i.e. if each SM and ME can be found, MT refers to each;
– = reminiscence area 2; is used when sending SMS previously saved by means of the command AT+CMSS; the storage to be despatched is completed with the command AT+CMGW and the three potential memory areas are all the time SM and ME;
– = reminiscence area 3, used to save lots of the brand new acquired SMS; it is determined by the AT+CNMI command despatched in the course of the initialization part of the GSM module; the memory areas are those defined above.
• AT command to delete SMS (Sms.SetCmd_AT_CMGD(uint8_t Index, uint8_t DelFlag)); it requires two parameters:
– = reminiscence location you need to delete;
– = command to execute, i.e.:
– “zero” deletes the SMS to the situation specified with the earlier parameter;
– “1” deletes all messages read with the AT+CPMS command from the required reminiscence;
– “2” deletes all messages already read or despatched however not these to be read or despatched;
– “3” deletes all messages already read, sent and in addition these nonetheless to be despatched;
– “Four” deletes all messages indiscriminately.
• AT command to learn the acquired SMS (Sms.SetCmd_AT_CMGR(uint8_t Index, uint8_t Mode)); also this requires two parameters:
– = memory location you need to read;
– = is used to vary or not the status of the read message, i.e. if the worth passed is “0” the standing of the read message is changed from “REC UNREAD” to “REC READ”, while in case you move the worth “1” the status of the learn message shouldn’t be modified.
The response is processed with a purpose to acquire information about the SMS acquired and particularly the text of the message. Other info is the telephone number from which it came and the standing of the message or “REC UNREAD”. (but to be learn) or ‘REC READ’. (already learn).
• AT command to send an SMS to a given telephone quantity (Sms.SetCmd_AT_CMGS(void)); do not cross parameters because each the telephone quantity and the text of the message to be sent are contained in two arrays that have to be initialized before calling the send command. The telephone number is in the “PhoneBook.PhoneNumber” array while the message text is in the “Sms.SmsText” array. A text message is shipped in two distinct phases: in the first part, the phone quantity to which the message is to be sent is shipped to the GSM module. Once the shape returns the symbol “> ” means you could proceed with sending the string containing the message to be despatched. The two phases are routinely managed by the library; we just have to worry about initializing the two arrays.
• AT command to put in writing a message to be sent to the memory among these chosen with the AT+CPMS command (Sms.SetCmd_AT_CMGW(void)). This command behaves precisely just like the previous one except that the SMS shouldn’t be sent but stored in the reminiscence of ME. Hence, the consumer has to worry about initializing the array with the telephone quantity and the array with the text to be saved. The arrays are the same as within the previous command.
• AT command to ship a message saved within the memory selected with the earlier command (Sms.SetCmd_AT_CMSS(uint8_t Index)). On this case, the parameter to be changed is the memory location by which it is stored.

Word that when the read command is executed, the GSM module returns the following parameters:
– = Memory sort; SM, ME or MT;
– = memory places occupied;
– = complete memory places out there; since these are three, the parameters described above are also repeated for memory 2 and three. The learn values are saved in a particular knowledge structure, one for each reminiscence. For instance, for memory 1 we have now the info construction “Sms_Mem1_Storage” which offers the gadgets “Sort”, “Used” and “Complete”.

With this overview we’ve got shown the AT instructions out there for the library file “SmsCmd_GSM.cpp”, keep in mind that there is the equal file .h containing the declarations of features, variables and knowledge buildings as well as AT commands saved in FLASH and used by the library. Keep in mind to activate the section for the administration of responses by the GSM module (ME) by means of the directive “ANSWER_SMS_AT_CMD_STATE_AT” within the file “Io_GSM.h”.
Let’s move on to a library file that handles both incoming and outgoing calls. The file is “PhonicCallCmd_GSM.cpp” and supplies the next commands.
• AT command to answer (PhonicCall.SetCmd_ATA(void)). It does not require the passage of parameters and the system realizes that a name is coming as a result of two distinct elements intervene. The primary is the interrupt generated by the RI sign related to the INT0 on the Arduino Uno board or INT4 on the Arduino Mega 2560 board. The RI signal is lively at 0 logic and subsequently the interrupt has been set to be activated when the signal goes from the excessive logic degree (IDLE) to the low logic degree or in other words using the downward fringe of the sign.
Throughout interrupt management, serial reception is activated to seize the despatched string as unsolicited end result code, which is processed by the Gsm.ProcessUnsolicitedCode() perform; as beforehand mentioned. A flag of the Gsm.GsmFlag knowledge structure and particularly the flag Gsm.GsmFlag.Bit.IncomingCall is then set. It is your duty to verify this bit and determine whether or not or to not answer the incoming voice call.
• AT command to shut the current name (PhonicCall.SetCmd_ATH(uint8_t Index)). This AT command requires a parameter if the module is a SIM900, SIM928A or M95. The parameter into account is outlined as and often, the value “0” is handed. Nevertheless, there are other instances during which it might be necessary to cross values aside from “zero” however that we at present do not use with our library. If you wish to know extra, consult the datasheet of the GSM module that implements and supports these further codes.
• AT command to initiate an outgoing voice name (PhonicCall.SetCmd_ATD(void)), this command does not need parameters as the telephone number to be handed to the command is loaded into the appropriate array “PhoneBook.PhoneNumber”. Before calling up this command it is advisable to examine that the GSM module (ME) shouldn’t be already occupied in another voice call using the AT+CPAS command already discussed above.
• AT command to initiate an outgoing voice name utilizing a telephone number within the phonebook (PhonicCall.SetCmd_ATD_PhoneNumberMemory(uint8_t n)). This command requires a parameter to point which reminiscence location incorporates the telephone quantity to use.
• AT command to initiate an outgoing voice name utilizing the telephone number of the earlier voice call (PhonicCall.SetCmd_ATDL(void)), no parameter required for this command.

Concerning the library file “PhonicCallCmd_GSM.cpp” we remind you that there’s the equivalent .h file containing the declarations of features, variables and knowledge buildings in addition to AT instructions saved in FLASH and used by the library. Keep in mind to activate the GSM module response administration part using the “ANSWER_PHONIC_CALL_AT_CMD_STATE” directive in the “Io_GSM.h” file.



Now let’s take a look at the library that manages the telephone guide. The associated file is “PhoneBookCmd_GSM.cpp” which supplies the instructions described under.
• AT command to pick the reminiscence for use for the telephone ebook, is just like the command used to pick the reminiscences for use for storing SMS. The command features a parameter to indicate on which sort of reminiscence you need to work (PhoneBookCmd_GSM.SetCmd_AT_CPBS(uint8_t TypeOfPhoneBook. bool Question)):
= knowledge string indicating the type of memory for use, which might be:
– = (ME), containing the record of calls made; the AT+CPBW command shouldn’t be applicable;
– = (SIM), memory containing emergency numbers; the AT+CPBW command just isn’t applicable to one of these memory;
– = (SIM) reminiscence that accommodates the telephone numbers that the consumer can call; it’s used to stop you from making calls to unwanted numbers, so all telephone numbers that are not on this listing cannot be referred to as (excluding emergency numbers and incoming calls);
– = (MT) accommodates the record of telephone numbers of missed calls; the AT+CPBW command just isn’t applicable to any such memory;
– = (SIM) incorporates the listing of your telephone numbers;
– = (MT) accommodates the listing of telephone numbers of acquired calls; the AT+CPBW command is just not relevant to any such memory;
– = (SIM) is the telephone e-book of the SIM and it can save you the specified telephone numbers in your software;
– = final number of any record;
– = (ME) is the telephone ebook of the GSM module and you can save the desired telephone numbers on your software;
– = (SIM) phonebook numbers excluded;
– = (SIM) phonebook service numbers;
– = (SIM) phonebook voice mail numbers;
– = (SIM) final phonebook.

In our software, we use SM memory to retailer your favourite telephone numbers. At present, the power to manage FD reminiscence just isn’t supported because it requires a further parameter, i.e. an entry password additionally referred to as PIN2.
The parameter to move to the AT command is of string sort, while to our perform we’ve to move an integer quantity and not using a signal that identifies which memory we need to use as decoded within the associated file .h. There’ll then be a perform that may extrapolate the suitable string given the assigned code. If you wish to use the command in read the question parameter have to be true, so the command will return a collection of information about the reminiscence presently in use: sort of reminiscence, variety of places used and the whole number of places.

The learn knowledge is saved in the PhoneBook.PhoneBookFlag knowledge construction.
• AT command to read the telephone ebook on the desired location; it has a parameter to point on which sort of memory to work (PhoneBookCmd_GSM.SetCmd_AT_CPBR(uint8_t Index. bool Question)):
– = index of the handle ebook to be learn; this command returns parameters together with:
– = index of the handle ebook;
– = telephone quantity within the telephone guide on the given index;
– = sort of number stored; if 161 nationwide number, if 145 international number (Use the “+” image on the prime of the number followed by the international code);
– = brief description assigned to the saved number.
The learn knowledge is saved in three variables, the first two of that are arrays, PhoneText – PhoneNumber – PhoneNumberType.
• Finally we now have the AT command to put in writing a telephone quantity to the chosen tackle ebook (PhoneBookCmd_GSM.SetCmd_AT_CPBW(uint8_t Index. uint8_t CmdType. uint8_t PhoneNumberType)). The parameters to be handed to the AT command are:
– : Index of the tackle ebook you need to write to
– : Telephone number to be saved in the telephone e-book
– : Quantity sort, see previous AT command
– : Textual content to assign to the saved quantity. For example, identify and surname



The phone quantity and the associated text have to be saved in the applicable arrays discussed before so that they can be inserted in the applicable spaces through the composition of the AT command.
The perform should then cross the index on which you need to save the telephone number, the type of the nationwide/international telephone number after which a parameter that identifies the type of command you need to execute: write the brand new telephone number in the selected tackle guide or delete the telephone number from the chosen handle e-book. Within the .h file, we’ve encoded unique codes that determine the write or delete command. This code have to be handed to the perform described. When deleting a telephone number from the phonebook, the AT command has solely the index as a parameter.
We’ve also accomplished the description of the AT instructions out there for the library file “PhoneBookCmd_GSM.cpp”; right here too there’s the equal .h file containing the declarations of features, variables and knowledge buildings as well as the AT commands saved in FLASH and utilized by the library. Keep in mind to activate the GSM module response administration part utilizing the “ANSWER_PHONEBOOK_AT_CMD_STATE” directive in the “Io_GSM.h” file.
We are going to finish this information introducing you to the library that deals with the administration of instructions associated to security, i.e. the management of passwords, PINs, and so on. The associated file is “SecurityCmd_GSM.cpp” and supplies the next commands.
• AT command to examine how many occasions the PIN/PUK code has been entered with out success in comparison with the variety of attempts allowed. This command differs in syntax between the three totally different manufacturers SIMCOM, FIBOCOM and QUECTEL. We then have (SecurityCall.SetCmd_ATQ_SPIC(void)) for SIMCOM, (SecurityCall.SetCmd_ATQ_TPIN(void)) for FIBOCOM and (SecurityCall.SetCmd_ATQ_QRTPIN(void)) for QUECTEL. In all instances, no parameters have to be handed to the AT command, only the right AT command have to be used depending on the GSM module selected. As a response from the GSM module (ME) you get the attempts already made for and .

These values are then saved in the SecurityFlag knowledge construction, exactly in SecurityFlag.Bit.PinRetry, SecurityFlag.Bit.Pin2Retry, SecurityFlag.Bit.PukRetry and SecurityFlag.Bit.Puk2Retry. It is then up to the consumer to use the read values to determine whether or to not try and ship the PIN or PUK code. We need to keep in mind you that this mechanism is used through the initialization as already extensively defined earlier than
• AT command to verify if the PIN code is required to unlock the SIM (SecurityCall.SetCmd_ATQ_CPIN(void)). The command does not require any parameters. As a response from the module we have now the next:
– : ME doesn’t require a PIN code. No action to be taken
– : ME is ready for the PIN code. Subsequently, earlier than sending the PIN code, it is advisable to make use of the AT command described above to examine how many makes an attempt can be found and then, if essential, ship the PIN code. Please word that the PIN and PUK codes are saved in EEPROM
– : ME is ready for the PUK code
– : ME is waiting for the anti-theft PIN code
– : ME is ready for the PUK code burglar alarm
– : ME is waiting for the PIN2 code. Have to be explicitly requested by way of the error code CME 17
– : ME is ready for the PUK2 code. Have to be explicitly requested by way of the error code CME 18
• AT command for sending the PIN or PUK code (SecurityCall.SetCmd_CPIN_PUK(uint8_t TypeOfCmd)). This AT command expects the PIN code or the PUK code followed by the new PIN code, then the perform have to be handed the action code you need to carry out or only PIN code or PUK code plus PIN code. Within the .h file, we have now encoded the varied working conditions. Relying on the motion chosen, the perform will learn from the EEPROM reminiscence the PIN code to be added to the AT command or the PUK code followed by the PIN code. It’s essential to make certain that you might have saved the PIN and PUK codes in EEPROM using the appropriate sketch. Subsequent time, we’ll show you the best way to do it.
• AT command to lock or unlock the obtainable community features with a password. The AT command requires the following parameters:
– : Community features that you simply need to block utilizing a password
– : If “0” unlocks, if “1” locks, if “2” checks the status of performance
– : Password string format
– : Class membership: “1” entry, “2” all providers, “4” fax and “7” all courses

The perform have to be handed two parameters which might be used to compose the specified AT command (SecurityCall.SetCmd_CLCK(uint8_t TypeOfFac, uint8_t Mode)). The primary parameter is a code that identifies the network performance you need to shield with a password. The codes are encoded in the .h file whereas the second parameter determines whether to execute a lock, unlock or a easy read query. The potential manageable community features are:
– : 4-Digits → Blocking all outgoing calls
– : Four-Digits → Blocking outgoing worldwide calls
– : 4-Digits → Blocking outgoing international calls apart from the nation of origin
– : 4-Digits → Blocking all incoming calls
– : Four-Digit → Block all incoming calls when roaming overseas
– : 4-Digit → Blocking of all providers
– : Blocking of all outgoing providers
– : Blocking of all incoming providers
– : SIM card memory lock containing solely the telephone numbers you’ll be able to call
– : Four/8-Digit → Lock SIM as for the PIN
– : 8-Digit → Community personalization
– : Eight-Digit → Network subset personalization
– : 8-Digit → Service Provider personalization
– : 4/8-Digit → SIM PIN 2
Every of the above codes has been coded with a singular quantity to be handed to the perform as described above.
As the final one, we’ve got an AT command to vary the set password (SecurityCall.SetCmd_CPWD(uint8_t TypeOfFac)). The one parameter to move to the perform is the type of community functionality you need to handle. The record made within the earlier command is valid, but just for: and, . The AT command subsequently expects the following parameters:
– : Community performance on which you need to change the password
– : Previous password
– : New password



Nicely, we now have deeply explained all the AT commands at present out there in our GSM defend module management library.


From openstore

GSM compact interface with M95

Miniature Module with SIM800

Small Breakout for SIM928 GSM&GPS Module

Common GSM Defend



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