Internet with A9G Low Power GPRS+GPS Module & Arduino

Overview: Internet with A9G Low Power GPRS+GPS Module

In this tutorial, we will learn about GPRS Internet Connectivity with A9G Low Power GPRS+GPS Module & Arduino. We will use the AT Commands to connect the A9G Module to Internet. As discussed in Previous Tutorial that A9G is low-powered GPRS GPS Module for IoT Applications, so we will use this module for a Simple IoT Projects.

There is no need for wifi rather Cellular IoT is preferred for Internet Connectivity. We will interface DHT11 Humidity Temperature Sensor with the Maduino Zero A9G board. We will then read the temperature and humidity data and send it wirelessly over Thingspeak Server.

But before moving ahead, I will highly recommend you to go through these basic getting started tutorials to learn more about Maduino A9G Board.
1. Getting Started with A9G Low Power GSM/GPRS+GPS Module with Arduino
2. GPS Tracker using A9G GPRS/GPS Module & Arduino

AT Commands for GPRS Internet Connections

Here are the list of few AT Commands that are required for GPRS Connectivity and data transmission over a TCP Protocol.

1	1. AT+CREG?

This command is used to check whether we are registered to the network or not. If it shows 1, 1 as a response then this means that we are registered and can move ahead.

1	2. AT+CGATT

This command is similar to the CREG command. If its response is 1 then we are connected to the network.

1	3. AT+CIPSTATUS

This command is used to check whether the IP is connected or Not. If its response is “INITIAL” then it means that we are connected. If it shows something else then there is some problem.

1	4. AT+CGDCONT=1

This command is used to connect to the Internet. In this command, we need to specify the APN and IP as well in the format given as AT+CGDCONT=1, “IP”, “www”

1	5. AT+HTTPGET

This command is used to send an HTTP get a request to any server link. Its format is AT+HTTPGET=”server link”.

1	6. AT+CIPMODE

This is used for selecting TCP/IP application mode. ‘0’ os non-transparent mode and ‘1’ is the transparent mode.

1	7. AT+CIPACK

This command checks the state of data transmission. It will return the amount of data sent, data acknowledged by the server, and data not confirmed by the server.

Getting Temperature Humidity data from DHT11 Sensor

Before Sending the Humidity Temperature Sensor Data directly to the Thingspeak Server using A9G GPRS Internet Connectivity, we need to learn how we can retrieve data from DHT11 Sensor and display it on OLED Display.

The Maduino A9G Board has a slot for 0.96″ I2C OLED Display where we can directly connect the OLED Display. Similarly, DHT11 Sensor has 3 pins VCC, GND & Signal. Connect the VCC to 3.3V, GND to GND & Signal to D3 of Maduino Zero A9G Board.

Now after the Hardware Setup is done, you can add the following libraries to the Arduino Library Folder. And then you can upload the below code to the Maduino Zero Board.

1. Adafruit GFX Library: https://github.com/adafruit/Adafruit-GFX-Library
2. SSD130 OLED Library: https://github.com/adafruit/Adafruit_SSD1306
3. DHT11 Library: https://github.com/adafruit/DHT-sensor-library

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#include <stdio.h>

#include <string.h>

#include <Wire.h>

#include <Adafruit_GFX.h>

#include <Adafruit_SSD1306.h>

#include <DHT.h>

#include <DHT_U.h>

//*******for senser **********

float humidity;//humidity

float temperature;//temperature

#define DHTPIN 3 //D3

#define DHTTYPE DHT11

DHT dht(DHTPIN, DHTTYPE);

String showString="";//

#define SCREEN_WIDTH 128 // OLED display width, in pixels

#define SCREEN_HEIGHT 64 // OLED display height, in pixels

// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

void(* resetFunc) (void) = 0; //declare reset function at address 0

#define DEBUG true

int PWR_KEY = 9;

int RST_KEY = 6;

int LOW_PWR_KEY = 5;

bool ModuleState=false;

unsigned long timeCount;

void setup()

{

dht.begin();//sensor begin

pinMode(PWR_KEY, OUTPUT);

pinMode(RST_KEY, OUTPUT);

pinMode(LOW_PWR_KEY, OUTPUT);

digitalWrite(RST_KEY, LOW);

digitalWrite(LOW_PWR_KEY, HIGH);

digitalWrite(PWR_KEY, HIGH);

SerialUSB.begin(115200);

//while (!SerialUSB)

{

; // wait for serial port to connect

}

Serial1.begin(115200);

SerialUSB.println("Start to run!");

/**

digitalWrite(PWR_KEY, LOW);

delay(3000);

digitalWrite(PWR_KEY, HIGH);

delay(5000);

ModuleState=moduleStateCheck();

if(ModuleState==false)//if it's off, turn on it.

{

digitalWrite(PWR_KEY, LOW);

delay(3000);

digitalWrite(PWR_KEY, HIGH);

delay(5000);

SerialUSB.println("Now turnning the A9/A9G on.");

}

**/

//GPS test

//sendData("AT+GPS=1", 1000, DEBUG);//1: turn on GPS 0:Turn off GPS

//sendData("AT+GPSRD=10", 1000, DEBUG);//Read NEMA information every 10 seconds

//sendData("AT+LOCATION=2", 1000, DEBUG);//AT+LOCATION=X //1:Get base address, 2:get gps address

//sendData("AT+CCID", 3000, DEBUG);

//sendData("AT+CREG?", 3000, DEBUG);

//sendData("AT+CGATT=1", 1000, DEBUG);

//sendData("AT+CGACT=1,1", 1000, DEBUG);

//sendData("AT+CGDCONT=1,\"IP\",\"CMNET\"", 1000, DEBUG);

//sendData("AT+CIPSTART=\"TCP\",\"www.mirocast.com\",80", 2000, DEBUG);

if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // Address 0x3D for 128x64

Serial.println(F("SSD1306 allocation failed"));

for (;;)

{

SerialUSB.println("Now reset the maduino zero");

delay(1000);

resetFunc();//restart

delay(20);

}

delay(500);

display.clearDisplay();

display.setTextSize(2);

display.setTextColor(WHITE);

display.setCursor(0, 0);

//Display static text

display.println("how2electronics.com");

display.println("A9/A9G GPS Tracker!");

display.display();

delay(2000);

timeCount=millis();

SerialUSB.println(" A9/A9G GPS Test Begin!");

display.clearDisplay();

}

void loop()

{

if(millis()-timeCount>1000)

{

humidity = dht.readHumidity();

temperature = dht.readTemperature();

SerialUSB.println("humidity is " + (String)humidity);

SerialUSB.println("temperature is " + (String)temperature);

//if (!isnan(humidity) && !isnan(temperature))

{

//SerialUSB.println("Read from DHT sensor!");

showString = "Humidity: " + (String)humidity + "%" + "\r\n" +"Temp.: "+(String)temperature + "C";

}

SerialUSB.println(showString);

display.clearDisplay();

display.setTextSize(2);

display.setTextColor(WHITE);

display.setCursor(0, 0);

display.println(showString);

display.display();

timeCount=millis();//refresh

}

while (Serial1.available() > 0) {

display.clearDisplay();

String cstring = Serial1.readString();

SerialUSB.print(cstring);//SerialUSB.write(Serial1.read());

display.setTextSize(2);

display.setTextColor(WHITE);

display.setCursor(0, 0);

display.println(cstring);

display.display();

yield();

}

while (SerialUSB.available() > 0) {

Serial1.write(SerialUSB.read());

yield();

}

bool moduleStateCheck()

{

int i = 0;

bool moduleState=false;

for (i = 0; i < 10; i++)

{

String msg = String("");

msg = sendData("AT", 1000, DEBUG);

if (msg.indexOf("OK") >= 0)

{

SerialUSB.println("A9/A9G Module had turned on.");

moduleState=true;

return moduleState;

}

delay(500);

}

return moduleState;

}

String sendData(String command, const int timeout, boolean debug)

{

String response = "";

Serial1.println(command);

long int time = millis();

while ((time + timeout) > millis())

{

while (Serial1.available())

{

char c = Serial1.read();

response += c;

}

if (debug)

{

SerialUSB.print(response);

}

return response;

}

After uploading the code, now you can see the DHT11 Temperature Humidity Data on OLED Display.

Setting up Thingspeak

Now we need to setup the Thingspeak Account. To set up Thingspeak follow the following Steps:

Step 1: Visit https://thingspeak.com/ and create your account by filling up the details.

Step 2: Create a New Channel by Clicking on “Channel” & fill up the following details as shown in the image below.

Step 3: Click on API Key, you will see the “Write API Key“. Copy the API Key. This is very important, it will be required in Code Part.

Step 4: You can click on the “Private View” & customize the display window as you want.

So, that’s all from the Thingspeak Setup Part. Now let us move to the programming Part.

Sending DHT11 Data to Thingspeak with Cellular IoT

Now lets use the AT command as discussed above to send the DHT11 Humidity Temperature Data to Thingspeak Server.

1 2	//********api write key**************** const String apiKey="J64BYZU52VGHMF2Q";

In the below code change the API Key from the line above.

1	sendData("AT+CGDCONT=1,\"IP\",\"ntnet\"", 3000, DEBUG);

This line appears twice in the code. from this line change the APN. Every Cellular Network Provider has the own APN. For example, I am in Nepal and I am using Nepal Telecom SIM Card, so its APN is ‘ntnet’. Contact your network provider to get the APN details.

1	//sendData("AT+CIPSTART=\"TCP\",\"www.how2electronics.com\",80", 2000, DEBUG);//

This code is only for sending the data to Thingspeak Server. In case if you want to send the data to any Server using TCP Connection, uncomment this line and remove the Thinspeak Server Line.

Here is a complete code for the A9G GPRS Internet Connection Project.

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#include <stdio.h>

#include <string.h>

#include <DHT.h>

#include <DHT_U.h>

//*******for senser **********

float humidity;//humidity

float temperature;//temperature

#define DHTPIN 3 //D3

#define DHTTYPE DHT11

DHT dht(DHTPIN, DHTTYPE);

void(* resetFunc) (void) = 0; //declare reset function at address 0

#define DEBUG true

int PWR_KEY = 9;

int RST_KEY = 6;

int LOW_PWR_KEY = 5;

bool ModuleState=false;

unsigned long timeCount;

//**********api write key******************

const String apiKey="J64BYZU52VGHMF2Q";

String showString="";

void setup()

{

pinMode(PWR_KEY, OUTPUT);

pinMode(RST_KEY, OUTPUT);

pinMode(LOW_PWR_KEY, OUTPUT);

digitalWrite(RST_KEY, LOW);

digitalWrite(LOW_PWR_KEY, HIGH);

digitalWrite(PWR_KEY, HIGH);

Serial1.begin(115200);

digitalWrite(PWR_KEY, LOW);

delay(3000);

digitalWrite(PWR_KEY, HIGH);

delay(10000);

SerialUSB.begin(115200);

SerialUSB.println("Hello!");

SerialUSB.println("There need some time to initialize!");

delay(16000);

dht.begin();//sensor begin

humidity = dht.readHumidity();

temperature = dht.readTemperature();

Serial1.begin(115200);

//while (!SerialUSB)

{

;// wait for serial port to connect

}

ModuleState=moduleStateCheck();

if(ModuleState==false)//if it's off, turn on it.

{

digitalWrite(PWR_KEY, LOW);

delay(3000);

digitalWrite(PWR_KEY, HIGH);

delay(10000);

SerialUSB.println("Now turnning the A9/A9G on.");

}

#if 1

//GPS test

sendData("AT+GPS=0", 1000, DEBUG);//1: turn on GPS 0:Turn off GPS

//GSM Test

sendData("AT+CCID", 3000, DEBUG); //get SIM

sendData("AT+CREG?", 3000, DEBUG);

sendData("AT+CGATT=1", 3000, DEBUG);

sendData("AT+CGACT=1,1", 3000, DEBUG);

sendData("AT+CGDCONT=1,\"IP\",\"ntnet\"", 3000, DEBUG);

sendData("AT+CSQ", 1000, DEBUG); //

//sendData("AT+CIPSTART=\"TCP\",\"www.how2electronics.com\",80", 2000, DEBUG);//

String cmdString= "AT+HTTPGET=\"http://api.thingspeak.com/update.json?api_key=" + apiKey + "&field1=" + (String)temperature +"&field2=" + (String)humidity + "&field3=0.0&field4=0.0" + "\"";

sendData(cmdString,5000,DEBUG);

#endif

timeCount=millis();

SerialUSB.println("A9/A9G Test Begin!");

}

void loop()

{

#if 1

if(millis()-timeCount>30000) //60000ms

{

humidity = dht.readHumidity();

temperature = dht.readTemperature();

SerialUSB.println("humidity is " + (String)humidity);

SerialUSB.println("temperature is " + (String)temperature);

//if (!isnan(humidity) && !isnan(temperature))

{

//SerialUSB.println("Read from DHT sensor!");

showString = "Humidity:" + (String)humidity + "%" + "\r\n" +"Temperature:"+(String)temperature + "C";

}

SerialUSB.println(showString);

sendData("AT+CGATT=1", 1000, DEBUG);

sendData("AT+CGACT=1,1", 1000, DEBUG);

sendData("AT+CGDCONT=1,\"IP\",\"Ntnet\"", 1000, DEBUG);

String cmdString= "AT+HTTPGET=\"http://api.thingspeak.com/update.json?api_key=" + apiKey + "&field1=" + (String)temperature +"&field2=" + (String)humidity + "&field3=0.0&field4=0.0" + "\"";

SerialUSB.println(cmdString);

sendData(cmdString,5000,DEBUG);

delay(5000);

timeCount=millis();//refresh

}

#endif

while (Serial1.available() > 0) {

String cstring = Serial1.readString();

SerialUSB.print(cstring);//SerialUSB.write(Serial1.read());

yield();

}

while (SerialUSB.available() > 0) {

Serial1.write(SerialUSB.read());

yield();

}

bool moduleStateCheck()

{

int i = 0;

bool state=false;

for (i = 0; i < 10; i++)

{

String msg = String("");

msg = sendData("AT", 1000, DEBUG);

if (msg.indexOf("OK") >= 0)

{

SerialUSB.println("A9/A9G Module had turned on.");

state=true;

return state;

}

delay(500);

}

return state;

}

String sendData(String command, const int timeout, boolean debug)

{

String response = "";

Serial1.println(command);

long int time = millis();

while ((time + timeout) > millis())

{

while (Serial1.available())

{

char c = Serial1.read();

response += c;

}

if (debug)

{

SerialUSB.print(response);

}

return response;

}

After uploading code to the Maduino Zero Board, open the Serial Monitor, the Serial Monitor will automatically start displaying the following events.