I have an ITEAD 3G module running off my arduino. It had been running fine for months but then stopped responding from commands given by my web server. I suspect some change was made to the HTTP Header protocol because now the commands are getting cut off. I believe this is to do with the software serial buffer size but I have already increased this to 256 in the softwareserial.h file.
How can I improve my code to prevent the buffer overflow?
// Included header files
#include <SoftwareSerial.h>
// AT command related
#define AT_CREG_QUERY ("AT+CREG?")
#define AT_CHTTPACT_COMMAND ("AT+CHTTPACT=\"%s\",%d")
#define AT_CHTTPACT_INIT_RESPONSE ("+CHTTPACT: REQUEST")
#define AT_CHTTPACT_DATA_RESPONSE ("+CHTTPACT: DATA,")
#define AT_CHTTPACT_DONE_RESPONSE ("+CHTTPACT:0")
#define EOS ('\0')
#define ESC (0x1A)
#define OK ("OK")
// GSM definitions
#define unoTXPin (5) // Uno -> GSM
#define unoRXPin (4) // Uno <- GSM
#define powerGSMPin (7)
#define GSMBaudRate (9600)
#define UnoBaudRate (9600)
SoftwareSerial gsmSerial(unoRXPin,unoTXPin);
#define TEST_REQUEST ("GET //itest.php HTTP/1.1\r\nHost:website.com:80\r\nContent-Length:0\r\n\r\n")
char aux_str [100];
int8_t answer;
int aux = 0;
int data_size = 0;
#define HOST_NAME ("website.com")
#define HOST_PORT (80)
void setup() {
// init sequence
Serial.begin(UnoBaudRate);
gsmSerial.begin(UnoBaudRate);
Serial.println("Turning GSM on");
gsm_power_on();
while( (sendATcommand(AT_CREG_QUERY, "+CREG: 0,1", 500) ||
sendATcommand(AT_CREG_QUERY, "+CREG: 0,5", 500)) == 0 );
Serial.println(F("GSM : Registered to network"));
Serial.println(F("GSM : Ready for AT command"));
}
void loop () {
sprintf(aux_str, AT_CHTTPACT_COMMAND, HOST_NAME, HOST_PORT);
Serial.println(F("\n*** Start HTTP Transaction ***\n"));
Serial.println(AT_CHTTPACT_INIT_RESPONSE);
answer = sendATcommand(aux_str, AT_CHTTPACT_INIT_RESPONSE, 60000);
Serial.println(aux_str);
if (answer == 1)
{
data_size = 0;
Serial.println(F("Sends Request:"));
Serial.println(TEST_REQUEST);
gsmSerial.println(TEST_REQUEST);
// Sends
aux_str[0] = ESC;
aux_str[1] = 0x00;
answer = sendATcommand(aux_str, AT_CHTTPACT_DATA_RESPONSE, 100000);
delay(2000);
if(answer == 1)
{
Serial.println(AT_CHTTPACT_DATA_RESPONSE);
while(gsmSerial.available() > 0) {
Serial.print((char)gsmSerial.read());
delay(5);
}
}
Serial.println(F("\n*** End HTTP Transaction ***\n"));
Serial.print(F("Memory Free : "));
Serial.println(memoryFree());
delay(30000); // halt
}
}
// variables created by the build process when compiling the sketch
extern int __bss_end;
extern void *__brkval;
// function to return the amount of free RAM
int memoryFree(){
int freeValue;
if((int)__brkval == 0)
freeValue = ((int)&freeValue) - ((int)&__bss_end);
else
freeValue = ((int)&freeValue) - ((int)__brkval);
return freeValue;
}
void gsm_power_on(){
uint8_t answer=0;
// checks if the module is started
answer = sendATcommand("AT", "OK", 2000);
if (answer == 0)
{
// power on pulse
digitalWrite(powerGSMPin,HIGH);
delay(200);
digitalWrite(powerGSMPin,LOW);
delay(6000);
// waits for an answer from the module
while(answer == 0){
// Send AT every two seconds and wait for the answer
answer = sendATcommand("AT", OK, 2000);
}
}
}
int8_t sendATcommand(char* ATcommand, char* expected_answer1,
unsigned int timeout)
{
uint8_t x=0, answer=0;
char response[100];
unsigned long previous;
memset(response, EOS, 100); // Initialize the string
delay(100);
while( gsmSerial.available() > 0) gsmSerial.read(); // Clean the input buffer
gsmSerial.println(ATcommand); // Send the AT command
x = 0;
previous = millis();
// this loop waits for the answer
do{
if(gsmSerial.available() != 0){
response[x] = gsmSerial.read();
x++;
// check if the desired answer is in the response of the module
if (strstr(response, expected_answer1) != NULL)
{
answer = 1;
}
}
// Waits for the asnwer with time out
}
while((answer == 0) && ((millis() - previous) < timeout));
return answer;
}
int8_t sendATcommand2(char* ATcommand, char* expected_answer1,
char* expected_answer2, unsigned int timeout)
{
uint8_t x=0, answer=0;
char response[100];
unsigned long previous;
memset(response, EOS, 100); // Initialize the string
delay(100);
while( gsmSerial.available() > 0) gsmSerial.read(); // Clean the input buffer
Serial.println(ATcommand); // Send the AT command
x = 0;
previous = millis();
// this loop waits for the answer
do{
if(gsmSerial.available() != 0){
response[x] = gsmSerial.read();
x++;
// check if the desired answer is in the response of the module
if (strstr(response, expected_answer1) != NULL)
{
answer = 1;
}
// check if the desired answer is in the response of the module
if (strstr(response, expected_answer2) != NULL)
{
answer = 2;
}
}
// Waits for the asnwer with time out
}
while((answer == 0) && ((millis() - previous) < timeout));
return answer;
}
Example of response
+CHTTPACT: DATA,
660
http/1.1 200 ok
server: nginx/1.12.0
date: wed, 14 jun 2017 01:31:41 gmt
content-type: text/html; charset=utf-8
content-length: 416
connection: keep-alive
vary: accept-encoding
x-acc-exp: 600
x-proxy-cache: hit website.com
<!DOCT
*** End HTTP Transaction ***
The cut off happens when it starts to read the html of the website.
I also get the following response where it does not even begin to read the html. I believe this is because the transfer-encoding is 'chunked' but I'm not sure how to solve this. Or it could still just be the bugger size.
+CHTTPACT: DATA,
571
http/1.1 200 ok
server: nginx/1.12.0
date: wed, 14 jun 2017 01:34:46 gmt
content-type: text/html; charset=utf-8
transfer-encoding: chunked
connection: keep-alive
vary: accept-encoding
x-acc-exp: 600
x-proxy-cache: hit website.com
*** End HTTP Transaction ***
and another buffter overflow
+CHTTPACT: DATA,
575
http/1.1 200 ok
server: nginx/1.12.0
date: wed, 14 jun 2017 01:34:09 gmt
content-type: text/html; charset=utf-8
transfer-encoding: chunked
connection: keep-alive
vary: accept-encoding
x-acc-exp: 600
x-proxy-cache: expired website.co
*** End HTTP Transaction ***