Arduino GSM receiving text and then storing value as a variable in code

Question

I am using an Arduino Mega board with a SIM900 GSM.

My goal is to be able to text the GSM with a value of two digits (ex: 79) and then store that value as a variable in the code. I know how to set up the Mega and the GSM in terms of wiring and initialization of ports, but how would I write a short function to test the incoming values and save them to a variable?

I thought about testing each bit individually, storing each one as a separate variable, and then adding them for the total. For example, if the GSM received "#79" as a text I stored the value 7 as an integer variable named One and the value 9 as an integer variable named Two. Then I did

Total = (One*10)+Two. 

I am posting my code below that used this method, although it has not proved to be useful. If anyone has any suggestions I would greatly appreciate it.

#include <SoftwareSerial.h> //GSM Library 
int Max_temp; 
float threshold; 
SoftwareSerial SIM900(18, 19); 
String destinationNumber = "[phone]"; 
String outMessage1 = "Please enter the maximum desired room temp"; 
char inchar; // Will hold the incoming character from the GSM shield when user texts it 
int M_one;
int M_zero;
void GSM_SEND_MAX(); 
void GSM_RECEIVE_MAX(); 
void setup() 
{
 Serial.begin(9600); 
//GSM setup: 
 Serial1.begin(19200); // wake up the GSM shield
 delay(20000); // give time to log on to network.
 Serial1.print("AT+CMGF=1\r"); // set SMS mode to text
 delay(100);
 Serial1.print("AT+CNMI=2,2,0,0,0\r"); // blurt out contents of new SMS upon receipt to the GSM shield's serial out
 delay(100);
}// end void set up() 
void loop() 
{
 GSM_SEND_MAX();
 GSM_RECEIVE_MAX();
}// end void loop ()
/////Functions 
void GSM_SEND_MAX() 
{
 Serial.println("sending text"); 
 Serial1.begin(19200); 
 delay(20000); // give time to log on to network.
 Serial1.print("AT+CMGF=1\r");
 delay(1000);
 Serial1.println("AT + CMGS = \"" + destinationNumber +"\"");
 delay(1000);
 Serial1.print(outMessage1);
 delay(1000);
 Serial1.write((char)26); //ctrl+z
 delay(1000);
 Serial.println("send text");
}//end GSM_SEND_MAX funtion 
void GSM_RECEIVE_MAX() 
{
 //If a character comes in from the cellular module...
 while (Serial1.peek() != '#' ) 
 {
 inchar=Serial1.read(); 
 Serial.print("bad char "); 
 Serial.println(inchar); 
 delay(500);
 }// end while #1 
 inchar=Serial1.peek(); 
 Serial.println("out of loop 1"); 
 Serial.println(inchar); 
 while (Serial1.available() != 0) //While #2 reads incoming char 
 {
 Serial.println("in loop 2"); 
 inchar=Serial1.read(); 
if (inchar=='#') 
 {
 delay(10);
 Serial.print("got #"); 
 M_one=Serial1.read(); 
 if (M_one >= 0 )
 {
 delay(10);
 Serial.println();
 Serial.print("got M_one"); 
 Serial.print(M_one);
 M_zero=Serial1.read(); 
 if (M_zero >= 0)
 {
 Serial.println();
 Serial.print("got M_zero"); 
 Serial.print(M_zero); 
 }//end m_zero 
 }//end m_one 
 Max_temp = (M_one *10) + M_zero; 
 Serial.println();
 Serial.print("Max_temp=");
 Serial.print(Max_temp); 
 } //end if (inchar==#)
 }// end while #2 loop 
}//end GSM_RECEIVE_MAX function

• uint128_t: There is a code formatting button in the post editor. Highlight your code and click the {} button.
• Mikael Falkvidd: The code uses a char as int without conversion. See electronics.stackexchange.com/questions/38845/… for details on how to convert.