Arduino sketch unexpected behaviour

Question

I am currently in a arduino project to read some parameters from another microcontroller serially and the arduino is supposed to transmit these serially to dweet.io cloud. I use SIM900 modem for this. But my problem is that if i put some data to the variables, then the post to the cloud becomes unsuccessfull. Without any data in all parameters, the code runs fine.

Please find the code

char code[4] = {'0円'}, voltage[4] = {'0円'}, current[4] = {'0円'}, mcurrent[4] = {'0円'}, acurrent[4] = {'0円'}, power[4] = {'0円'}, pf[4] = {'0円'}, freq[4] = {'0円'}, temp[4] = {'0円'};
const char APN[18] = "bsnlnet";
byte dtype = 0;
#include <avr/pgmspace.h>
void read_comp() {
 byte flag = 0, index = 0, l = 0;
 char c;
 char readings[8] = {'0円'};
 dtype = 0;
 do {
 while (Serial.available() && l == 0) {
 c = Serial.read();
 delay(20);
 if (c == '\n') {
 l = 1;
 break;
 } else {
 readings[index] = c;
 index++;
 }
 }
 readings[index] = '0円';
 index = 0;
 l = 0;
 if (readings[0] == 'v' || readings[0] == 'V') { //check if received reading is voltage
 dtype = 1;
 flag = 1;
 if (readings[1] == 'o') {
 flag = 100;
 }
 } else if (readings[0] == 'c' || readings[0] == 'C') { //check if received reading is current
 dtype = 2;
 flag = 1;
 if (readings[1] == 'u') {
 flag = 100;
 }
 } else if (flag == 1 && readings[1] == 'o') {
 dtype = 9;
 flag = 100;
 } else if (readings[0] == 'm' || readings[0] == 'M') {
 dtype = 3;
 flag = 1;
 if (readings[1] == 'c' && flag == 1) {
 flag = 100;
 }
 } else if (readings[0] == 'a' || readings[0] == 'A') {
 dtype = 4;
 flag = 1;
 if (readings[1] == 'c') {
 flag = 100;
 }
 } else if (readings[0] == 'p' || readings[0] == 'P') {
 flag = 1;
 if (readings[1] == 'o') {
 flag = 100;
 dtype = 5;
 } else if (readings[1] == 'f' || readings[1] == 'F') {
 flag = 100;
 dtype = 6;
 }
 } else if (readings[0] == 'f' || readings[0] == 'F') {
 dtype = 7;
 flag = 1;
 if (readings[1] == 'r') {
 flag = 100;
 }
 } else if (readings[0] == 't' || readings[0] == 'T') {
 dtype = 8;
 flag = 1;
 if (readings[1] == 'e') {
 flag = 100;
 }
 }
 if (flag == 100) {
 switch (dtype) {
 case 1:
 voltage[0] = readings[3];
 voltage[1] = readings[4];
 voltage[2] = readings[5];
 voltage[3] = readings[6];
 voltage[4] = '0円';
 flag = 0;
 break;
 case 2:
 current[0] = readings[3];
 current[1] = readings[4];
 current[2] = readings[5];
 current[3] = readings[6];
 current[4] = '0円';
 flag = 0;
 break;
 case 3:
 mcurrent[0] = readings[3];
 mcurrent[1] = readings[4];
 mcurrent[2] = readings[5];
 mcurrent[3] = readings[3];
 mcurrent[4] = '0円';
 flag = 0;
 break;
 case 4:
 acurrent[0] = readings[3];
 acurrent[1] = readings[4];
 acurrent[2] = readings[5];
 acurrent[3] = readings[6];
 acurrent[4] = '0円';
 flag = 0;
 break;
 case 5:
 power[0] = readings[3];
 power[1] = readings[4];
 power[2] = readings[5];
 power[3] = readings[6];
 power[4] = '0円';
 flag = 0;
 break;
 case 6:
 pf[0] = readings[3];
 pf[1] = readings[4];
 pf[2] = readings[5];
 pf[3] = readings[6];
 pf[4] = '0円';
 flag = 0;
 break;
 case 7:
 freq[0] = readings[3];
 freq[1] = readings[4];
 freq[2] = readings[5];
 freq[3] = readings[6];
 freq[4] = '0円';
 flag = 0;
 break;
 case 8:
 temp[0] = readings[3];
 temp[1] = readings[4];
 temp[2] = readings[5];
 temp[3] = readings[6];
 temp[4] = '0円';
 flag = 0;
 break;
 case 9:
 code[0] = readings[3];
 code[1] = readings[4];
 code[2] = readings[5];
 code[3] = readings[6];
 code[4] = '0円';
 dtype = 10;
 flag = 0;
 break;
 }
 }
 } while (dtype != 10);
}
void modem_initialization(void) {
 char rec_data, r;
 byte network_status = 0 ;//network_status initialized as zero
 byte status_check = 0 ;//status_check initialized as zero
 byte Serial3_cnt = 0;//Serial3_cnt initialized as zero
 byte ok_flag = 0; //ok_flag initialized as zero
 byte count = 0; //count initialized as zero
 clear_rx_buffer();
 while (Serial3_cnt < 4) { // repeat entire loop until Serial3_cnt less than 5
 switch (Serial3_cnt) {
 case 0:
 clear_rx_buffer();//clearing receiving buffer
 Serial3.println(F("AT"));// Attention command to wake up Serial3 modem
 delay(1000);
 break;
 case 1:
 clear_rx_buffer();//clearing receiving buffer
 Serial3.println(F("ATE0"));//Command for disable echo
 delay(1000);
 break;
 /*case 2: clear_rx_buffer();//clearing receiving buffer
 // Serial3.println("ATV0");// Command for numeric response after this '0'(zero) will be recieved instead of "OK"
 delay(1000);
 break;*/
 case 2:
 clear_rx_buffer();//clearing receiving buffer
 Serial3.println(F("AT&W"));// Command TO SAVE SETTINGS
 delay(1000);
 break;
 case 3:
 Serial3_cnt = 4;// exit from the loop
 break;
 default :
 break;
 }
 while (Serial3.available() > 0) {
 rec_data = Serial3.read();
 if (rec_data == 'O') { // 'o' is recieved
 ok_flag = 1;
 } else if (ok_flag == 1 && rec_data == 'K') { // 'K' is recieved
 Serial3_cnt ++;
 ok_flag = 0;
 } else if (rec_data == '0') { // '0'(zero) is recieved (numeric response)
 Serial3_cnt ++;
 ok_flag = 0;
 } else if (rec_data == '+') { // '+' is recieved message
 clear_rx_buffer();
 if (Serial3_cnt > 0) {
 Serial3_cnt --;
 }
 }
 }
 }
 Serial3_cnt = 0;
 ok_flag = 0;
 while (network_status == 0) { //wait for PIN READY
 if (status_check == 0) {
 delay(1000);
 status_check = 1 ;
 clear_rx_buffer();
 Serial3.println(F("AT+CPIN?")); //checkin PIN return ready(+CPIN: READY) with a valid simcard otherwise error
 }
 while (Serial3.available() > 0) {
 rec_data = Serial3.read();
 if (rec_data == '+' && status_check == 1) { // '+' is recieved
 status_check = 2 ;
 } else if (rec_data == 'C' && status_check == 2) { // 'C' is recieved
 status_check = 3 ;
 } else if (rec_data == 'P' && status_check == 3) { // 'P' is recieved
 status_check = 4 ;
 } else if (rec_data == 'I' && status_check == 4) { // 'I' is recieved
 status_check = 5 ;
 } else if (rec_data == 'N' && status_check == 5) { // 'N' is recieved
 status_check = 6 ;
 } else if (rec_data == ':' && status_check == 6) { // ':' is recieved
 status_check = 7 ;
 } else if (rec_data == ' ' && status_check == 7) { // ' ' is recieved
 status_check = 8 ;
 } else if (rec_data == 'R' && status_check == 8) { // 'R' is recieved
 status_check = 9 ;
 } else if (rec_data == 'E' && status_check == 9) { // 'E' is recieved
 status_check = 10 ;
 } else if (rec_data == 'A' && status_check == 10) { // 'A' is recieved
 status_check = 11 ;
 } else if (rec_data == 'D' && status_check == 11) { // 'D' is recieved
 status_check = 12 ;
 } else if (rec_data == 'Y' && status_check == 12) { // 'Y' is recieved
 status_check = 13 ;
 } else if (rec_data == 0X0D && status_check == 13) { //Carriage return
 status_check = 14 ;
 } else if (rec_data == 0X0A && status_check == 14) { //Line Feed
 status_check = 15 ;
 } else if (rec_data == 'O' && status_check == 15) { // '0' is recieved
 status_check = 16;
 } else if (rec_data == 'K' && status_check == 16) {
 clear_rx_buffer();
 status_check = 0 ;
 network_status = 1; //goto next step
 } else if (rec_data != 'R' && status_check == 8) { //+CPIN: NOT READY
 clear_rx_buffer();
 status_check = 0 ;
 network_status = 0; //repeat current step
 } else if (rec_data == 'M' && status_check == 3) { // in case of any message
 clear_rx_buffer();
 status_check = 0 ;
 network_status = 0; //repeat current step
 }
 }
 }
 while (network_status == 1) { //wait for SIM network registration
 if (status_check == 0) {
 delay(1000);
 status_check = 1 ;
 clear_rx_buffer();
 Serial3.println(F("AT+CREG?")); //checking for SIM card registration ,if registerd "+CREG: 0,1" will receive
 }
 while (Serial3.available() > 0) {
 rec_data = Serial3.read();
 if (rec_data == '+' && status_check == 1) { // '+' is recieved
 status_check = 2 ;
 } else if (rec_data == 'C' && status_check == 2) { // 'C' is recieved
 status_check = 3 ;
 } else if (rec_data == 'R' && status_check == 3) { // 'R' is recieved
 status_check = 4 ;
 } else if (rec_data == 'E' && status_check == 4) { // 'E' is recieved
 status_check = 5 ;
 } else if (rec_data == 'G' && status_check == 5) { // 'G' is recieved
 status_check = 6 ;
 } else if (rec_data == ':' && status_check == 6) { // ':' is recieved
 status_check = 7 ;
 } else if (rec_data == ' ' && status_check == 7) { // ' ' is recieved
 status_check = 8 ;
 } else if (rec_data == '0' && status_check == 8) { // '0' is recieved
 status_check = 9 ;
 } else if (rec_data == ',' && status_check == 9) { // ',' is recieved
 status_check = 10 ;
 } else if (rec_data == '1' && status_check == 10) { // '1' is recieved
 status_check = 11 ;
 } else if (rec_data == 0X0D && status_check == 11) { //Carriage return
 status_check = 12 ;
 } else if (rec_data == 0X0A && status_check == 12) { //Line Feed
 status_check = 12 ;
 } else if (rec_data == 'O' && status_check == 12) { // '0' is recieved
 status_check = 13;
 } else if (rec_data == 'K' && status_check == 13) {
 clear_rx_buffer();
 status_check = 0 ;
 network_status = 2; //goto next step
 } else if (rec_data != '1' && status_check == 10) { // +CREG: 0,2 not registered
 clear_rx_buffer();
 status_check = 0 ;
 network_status = 1; //repeat current step
 } else if (rec_data == 'M' && status_check == 3) { // in case of any message
 clear_rx_buffer();
 status_check = 0 ;
 network_status = 1; //repeat current step
 }
 }
 }
 Serial3_cnt = 0;
 while (Serial3_cnt < 4) { // repeat entire loop until Serial3_cnt less than 4
 switch (Serial3_cnt) {
 case 0:
 clear_rx_buffer();//clearing receiving buffer
 Serial3.println(F("AT+CMGF=1"));// Attention command to wake up Serial3 modem
 delay(1000);
 break;
 case 1:
 clear_rx_buffer();//clearing receiving buffer
 Serial3.println(F("AT+CNMI=2,1,0,0,0"));//Command to configure new message indication
 delay(1000);
 break;
 case 2:
 clear_rx_buffer();//clearing receiving buffer
 Serial3.println(F("AT+CMGD=1,4"));// Command to delete all received messages
 delay(1000);
 break;
 case 3:
 Serial3_cnt = 4;// exit from the loop
 break;
 default :
 break;
 }
 while (Serial3.available() > 0) {
 rec_data = Serial3.read();
 if (rec_data == 'O') { // '0'(zero) is recieved (numeric response)
 rec_data = Serial3.read();
 if (rec_data == 'K') {
 Serial3_cnt ++;
 }
 } else if (rec_data == '+') { // '+' recieved ,before "AT+CIICR" command,may be any message
 clear_rx_buffer();
 if (Serial3_cnt > 0) {
 Serial3_cnt --;
 }
 } else if (rec_data == 'E' && Serial3_cnt > 2) { // '4' recieved (error),in gprs initialisation commands
 clear_rx_buffer();
 Serial3_cnt = 4;
 }
 }
 }
 Serial3_cnt = 0;
}
void clear_rx_buffer(void) {
 Serial3.flush();
}
void gprs_init() {
 byte st = 1, i = 0, response = 0;
 char r[10];
 while (st <= 9) {
 delay(1000);
 clear_rx_buffer();
 switch (st) {
 case 1:
 Serial3.println(F("AT+CGATT?"));
 break;
 case 2:
 Serial3.println(F("AT+CIPSHUT"));
 break;
 case 3:
 Serial3.println(F("AT+CIPMUX=0"));
 break;
 case 4:
 response = cmd1_check(1);
 break;
 case 5:
 Serial3.println(F("AT+CIICR"));
 delay(1000);
 break;
 case 6:
 Serial3.println(F("AT+CIFSR"));
 break;
 case 7:
 response = cmd1_check(2);
 delay(2200);
 clear_rx_buffer();
 break;
 case 8:
 Serial3.println(F("AT+CIPSEND"));
 break;
 case 9:
 Serial3_send();
 ++st;
 break;
 }
 if (st == 10) {
 clear_rx_buffer();
 }
 delay(1000);
 while (Serial3.available() && st < 9 && st != 7 && st != 4) {
 r[i] = Serial3.read();
 i++;
 }
 i = 0;
 if (strstr(r, "ALREADY") != NULL) {
 Serial3.println("AT+CIPSHUT");
 delay(50);
 clear_rx_buffer();
 st = 2;
 r[0] = '0円';
 }
 if (strstr(r, "OK") != NULL || strstr(r, "+CGATT") != NULL || (strstr(r, ".") != NULL && st == 6) || strstr(r, ">") != NULL) {
 st++;
 } else if (strstr(r, "ERR") != NULL) {
 break;
 } else if (response == 1 && (st == 7 || st == 4)) {
 st++;
 response = 0;
 }
 }
}
char cmd1_check(short int o) {
 byte timout1 = 10500, m1, p1 = 0, resp1 = 0;
 char response1[25] = {'0円'};
 m1 = millis();
 clear_rx_buffer();
 if (o == 1) {
 Serial3.print(F("AT+CSTT="));
 Serial3.print('"');
 Serial3.print(APN);
 Serial3.print('"');
 Serial3.print(',');
 Serial3.print('"');
 Serial3.print('"');
 Serial3.print(',');
 Serial3.print('"');
 Serial3.println('"');
 delay(3000);
 } else if (o == 2) {
 Serial3.print(F("AT+CIPSTART="));
 Serial3.print('"');
 Serial3.print(F("TCP"));
 Serial3.print('"');
 Serial3.print(',');
 Serial3.print('"');
 Serial3.print(F("dweet.io"));
 Serial3.print('"');
 Serial3.print(',');
 Serial3.println(80);
 delay(2000);
 }
 do {
 p1 = 0;
 while (Serial3.available()) {
 response1[p1] = Serial3.read();
 p1++;
 delay(20);
 }
 if (strstr(response1, "OK") != NULL && o == 1) {
 resp1 = 1;
 } else if (strstr(response1, "ERR") != NULL) {
 resp1 = 2;
 } else if (strstr(response1, "CONNECT OK") != NULL && o == 2) {
 resp1 = 1;
 }
 } while ((millis() - m1) <= timout1 && resp1 == 0);
 return (resp1);
}
void Serial3_send() {
 Serial3.print("POST /dweet/for/");
 Serial3.print("mythingname");
 Serial3.print("?vo=");
 Serial3.print(voltage);
 Serial3.print("&cu=");
 Serial3.print(current);
 Serial3.print("&Mc=");
 Serial3.print(mcurrent);
 Serial3.print("&Ac=");
 Serial3.print(acurrent);
 Serial3.print("&Po=");
 Serial3.print(power);
 Serial3.print("&PF=");
 Serial3.print(pf);
 Serial3.print("&fr=");
 Serial3.print(freq);
 Serial3.print("&Te=");
 Serial3.print(temp);
 Serial3.println(" HTTP/1.1");
 Serial3.println("connection: keep-alive");
 Serial3.println();
 Serial3.println();
 Serial3.write(26);
 Serial3.println();
 delay(10000);
 Serial3.println("AT+CIPSHUT");
 delay(50);
}
void setup() {
 Serial.begin(9600);
 Serial3.begin(9600);
 modem_initialization();
}
void loop() {
 dtype = 0;
 read_comp();
 gprs_init();
}

Answer 1

This looks like you are constructing the data to be sent as GET parameters (i.e as part of the querystring), whereas I believe dweet.io expects them as part of the POST body - as seen here.

There seem to be many people struggling to successfully send HTTP POSTs with a SIM900, but I think this answer outlines the correct sequence to make it work.