Arduino +ESP8266 sending POST once but fails every other time - c++

Question

I'm using esp8266 with my arduino Mega and controlling it over serial with AT commands( i know that it is not the best way of working with ESP but I didn't know how to do it other way)...So my problem is that I have my POST request formulated and send over to my webpage ....It works fine at first try ,but after that, in every loop try, it fails...Please can someone check my code and see if you can find some error that can cause this?
This is my function for sending data:
void SendData(){
cmd = "AT+CIPSTART=\"TCP\",\"";
cmd+= server;
cmd+="\",80";
Serial1.println(cmd);
Serial.println(cmd);
delay(1000);
if(Serial1.find("OK"))
{
Serial.println("\r\nReady to send data!");
}
String retazec="cz="+cas_zaznamu; ////DATA from sensors etc.
retazec=retazec+"&tep="+t;
retazec=retazec+"&vlhv="+vv;
retazec=retazec+"&vlhp="+vp;
retazec=retazec+"&zav="+za;
retazec=retazec+"&kur="+ku;
retazec=retazec+"&vet="+ve;
retazec=retazec+"&pz="+datum_zavlaha;
int retazec_len=retazec.length();
retazec.toCharArray(retaz,70);
cmd = "POST /arduino.php"; ////POST request
cmd+=" HTTP/1.1\r\n";
cmd+="Host: myhost.com\r\n";
cmd+="Content-Type: application/x-www-form-urlencoded\r\n";
cmd+="Connection:Close\r\n";
cmd+="Content-Length: ";
cmd+=retazec_len;
cmd+="\r\n\r\n";
int size=cmd.length()+retazec_len+2;
Serial1.print("AT+CIPSEND=");
Serial1.println(size);
Serial.print("AT+CIPSEND=");
Serial.println(size);
delay(2000);
if (Serial1.find(">")){
Serial.println("Sending data...");
} else {
Serial1.println("AT+CIPCLOSE");
Serial.println("COnnection closed");
return;
}
Serial.print(cmd);
Serial1.print(cmd);
for(int i=0;i<=retazec_len;i++){
Serial.print(retaz[i]);
Serial1.print(retaz[i]);
}
Serial1.print("\r\n");
if(Serial1.find("OK"))
{
Serial.println("Succesfuly send!");
}
ReadString(); /// emptying the buffer by reading serial1
delay(5000);
Serial.println("-----end");
}
Also I have different function for GET request ,very similar to the one above , and that one worked multiple times in a row(dont want to say every time bcs it was running only for few minutes).
Please please any suggestions will be deeply appreciated. :)

Answer 1

My educated guess:The String class in combination with at commandsTry to get rid of the String class in webbased scenarios. Reason: You want to have a stable environment running for a long time. String class uses heap memory to dynamicly build and destroy the underlying structures it needs for e.g. append strings (... = .. + .. + ..). As there is no so called garbagge collection (and would have not enough memory anyway) the relativeley small memory is cut into small units, in which (at a certain length) the String does not fit anymore -> crash, reset => lost POST or GET request.Use fixed global char array(s) to build your messages, these are compiled into the flash and stop the "memory bleeding". Enclosed an example (although I dont understand - from your language - the name or the content of variables and with no type given I had to guess)
char retazec[256] = {'\0'}; /* Defined globally - Used for retazec functions max 255 chars */
char cmd[512] = {'\0'}; /* Defined globally - Used for POST/GET functions max 511 chars */
char numBuffer[16] = {'\0'}; /* Defined globally - Used for uint32_t or smaller number conversions to char */
unsigned long timeStamp = 0;
unsigned long delayTime = 2000;
setup(){...}
//The parts you gave "translated"into char manuipulation
const char* cmdStart[] = "POST /arduino.php HTTP/1.1\r\n Host: myhost.com\r\nContent-Type: application/x-www-form-urlencoded\r\nConnection:Close\r\nContent-Length: ";
const char* cmdEnd[] = "\r\n\r\n";
strcpy (retazec, "cz=");
itoa(cas_zaznamu, numBuffer, 10); // convert int DATA from sensors etc.
// If its a float use this command
// dtostrf(floatvar, StringLengthIncDecimalPoint, numVarsAfterDecimal, charbuf);
// dtostrf(cas_zaznamu, 3, 2, numBuffer); // -> xx.xx
strcat(retazec, numBuffer);
strcat(retazec, "&tep=");
itoa(t, numBuffer, 10);
// or dtostrf(t, 4, 2, numBuffer); // -> xxx.xx
strcat(retazec, numBuffer);
strcat(retazec, "&vlhv=");
....
// ... till datum_zavlaha;
int retazec_len=strlen(retazec); // gives you the length
// not needed we have a char array allready retazec.toCharArray(retaz,70);
strcpy(cmd, cmdStart);
iota (retazec_len, numBuffer);
strcat(cmd, numBuffer);
strcat(cmd, cmdEnd);
int size=strlen(cmd)+retazec_len+2;
if (millis() - timeStamp > delayTime) {
Serial1.print("AT+CIPSEND=");
Serial1.println(size);
Serial.print("AT+CIPSEND=");
Serial.println(size);
timeStamp = millis();
}
// NO NEVER delay(2000);
if (Serial1.find(">")){
Serial.println("Sending data...");
} else {
Serial1.println("AT+CIPCLOSE");
Serial.println("COnnection closed");
return;
}
The second issue is delay (it stops processing dead in its tracks) So the cpu waits in your case 2 sec before restarting - not a clever idea when using communication protocols. I implemented a non-blocking delay - if you need it somewhere else as I said you only gave fragments of code
EDIT after OPs feedback
String class as a whole should be avoided in dynamic communication scenarios so in all parts of the programm.Should I use one big string (small s = char array) thats just coping what the original code does but instead of String with char array. So imho the structure has just to be adapted to char array without big changes (exept expicitly converting numbers to char) Btw the same takes place when you add a variable to String
uint8_t aNumber = 12;
String myBigString = "A number is " + aNumber;
does internally in the String library the same as
uint8_t aNumber = 12;
char numBuffer [16] = {'\0'} ;
char myBigString [32] = {'\0'} ;
strcpy (myBigString, "A number is ");
iota (aNumber, numBuffer, 10);
strcat (myBigString, numBuffer);
The difference is - you write the lines instead of lazely using a bad library but with full control over memory and the advantage to compile it to flash, saving memory. Const char are actually called via pointer - so for later there are functions to get only certain parts of an array handy to create variable messages out of one big array.After a code analysis on github there is one other big problem: The use of blocking delay():
loop() {
delay(1000);
// lot of code
delay(3000);
}
replace with a non blocking delay
unsigned long timeStamp = 0;
setup(){}
loop() {
if (millis() - timeStamp > 4000) {
// lot of code
timeStamp = millis(); // reset the timer
}
}
and as written before get rid of all Strings (e.g)
///////////PREMENNE PRIJIMANÝCH ÚDAJOV///////
String mode;
String inzavlaha;
String inkurenie;
String invetranie;
String invlhkost_p;
String invlhkost_v;
String incas;
String intrvanie;
String inopakovanie;
String inteplota;
and as a final tio.If you want worldwide help, start to write all of your program in English (variables and comments) it makes it easier to help.