So I am now trying to move the building of the URL into a function and am having some trouble with getting it to compile. The code is the same basic layout as the example I was working on above, but now I am trying to pass 2 variables into the "writeThingspeak" function.
This will allow me to change the field number I'm writing to and the result that's being written easily. The full sketch as it stands currently is below:
/*
Web client
This sketch connects to the Thingspeal website using SSL through a MKR GSM 1400 board. Specifically,
this example downloads performs a write and read operation to the thingspeak channel specified in the
arduino_secrets.h file.
This sketch prints output to the Serial monitor.
Circuit:
* MKR GSM 1400 board
* Antenna
* SIM card with a data plan
created 05 Feb 2018
by SMGS
*/
// libraries
#include <MKRGSM.h>
#include <stdio.h>
#include <string.h>
#include "arduino_secrets.h"
// Please enter your sensitive data in the Secret tab or arduino_secrets.h
// PIN Number
const char PINNUMBER[] = SECRET_PINNUMBER;
// APN data
const char GPRS_APN[] = SECRET_GPRS_APN;
const char GPRS_LOGIN[] = SECRET_GPRS_LOGIN;
const char GPRS_PASSWORD[] = SECRET_GPRS_PASSWORD;
// Thingspeak Secret Settings
char writeapikey[] = secretwriteapikey;
char readapikey[] = secretreadapikey;
char channelid[] = secretchannelid;
// initialize the library instance
GSMSSLClient client;
GPRS gprs;
GSM gsmAccess;
GSMLocation location;
// Domain name and port that we will connect too (for example: api.thingspeak.com)
char server[] = "api.thingspeak.com";
int port = 443; // port 443 is the default for HTTPS
// Remainder of the URL is crafted together in the writeThingspeak() or readThingspeak() functions which take
// some arguments such as field and result, the crafted URL is returned from the function for later use.
char URL[200];
void setup() {
// initialize serial communications and wait for port to open:
Serial.begin(9600);
while (!Serial) {
; // wait for serial port to connect. Needed for native USB port only
}
Serial.println("Starting Arduino web client.");
// connection state
boolean connected = false;
// After starting the modem with GSM.begin()
// attach the shield to the GPRS network with the APN, login and password
while (!connected) {
if ((gsmAccess.begin(PINNUMBER) == GSM_READY) &&
(gprs.attachGPRS(GPRS_APN, GPRS_LOGIN, GPRS_PASSWORD) == GPRS_READY)) {
connected = true;
} else {
Serial.println("Not connected");
delay(1000);
}
}
}
void loop() {
char result = 200;
char field = 1;
Serial.println("Print the completed /crafted URL: ");
Serial.println(writeThingspeak(field,result));
// URL = writeThingspeak(field,result);
Serial.println("connecting...");
// if you get a connection, report back via serial:
if (client.connect(server, port)) {
Serial.println("Read connected");
// Make a HTTP request:
client.print("GET ");
client.print(URL);
client.println(" HTTP/1.1");
client.print("Host: ");
client.println(server);
client.println("Connection: close");
client.println();
} else {
// if you didn't get a connection to the server:
Serial.println("connection failed");
}
delay(200);
// if there are incoming bytes available
// from the server, read them and print them:
if (client.available()) {
char c = client.read();
Serial.print(c);
}
// do nothing forevermore:
for (;;)
;
//}
}
char writeThingspeak(char fieldNumber, char result) {
// An Complete Example URL to Update Channel Field1 via Thingspeak
// GET https://api.thingspeak.com/update?api_key=1234567890ABC&field1=0
// Our URL is broken down below to give us the ability to update certain portions of the URL, such as the field number etc
char writeURLField[200];
char thingspeak_write_update[17] = "/update?api_key=";
char thingspeak_write_field[8] = "&field";
//Build the custom Write URL to send data to my Thingspeak Channel via strcpy and strcat
strcpy (writeURLField,thingspeak_write_update);
strcat (writeURLField,writeapikey);
strcat (writeURLField,thingspeak_write_field);
strcat (writeURLField,fieldNumber);
strcat (writeURLField,"=");
strcat (writeURLField,result);
return writeURLField;
} //end of writeThingspeak
Where a couple of things have been declared within the "arduino_secrets.h" file as below:
#define SECRET_PINNUMBER ""
#define SECRET_GPRS_APN "internet" // replace your GPRS APN
#define SECRET_GPRS_LOGIN "" // replace with your GPRS login
#define SECRET_GPRS_PASSWORD "" // replace with your GPRS password
// Thingspeak Settings
#define secretwriteapikey "1234567890000002"
#define secretreadapikey "1234567890000001"
#define secretchannelid "123456"
This is probably the wrong way to do it, I say that as it gives me a few errors and won't compile. I suspect my issue has something to do with the fact that I'm using character arrays?
Compiler Issues:
Arduino: 1.8.5 (Windows 10), Board: "Arduino MKR GSM 1400"
20180202-5.ino: In function 'char writeThingspeak(char, char)':
20180202-5:130: error: invalid conversion from 'char' to 'const char*' [-fpermissive]
strcat (writeURLField,fieldNumber);
^
In file included from c:\appdata\local\arduino15\packages\arduino\tools\arm-none-eabi-gcc\4.8.3-2014q1\arm-none-eabi\include\stdlib.h:11:0,
from C:\AppData\Local\Arduino15\packages\arduino\hardware\samd\1.6.17\cores\arduino/Arduino.h:25,
from sketch\GsmSSLWebClient-20180202-5.ino.cpp:1:
c:\appdata\local\arduino15\packages\arduino\tools\arm-none-eabi-gcc\4.8.3-2014q1\arm-none-eabi\include\string.h:26:8: error: initializing argument 2 of 'char* strcat(char*, const char*)' [-fpermissive]
char *_EXFUN(strcat,(char *__restrict, const char *__restrict));
^
20180202-5:132: error: invalid conversion from 'char' to 'const char*' [-fpermissive]
strcat (writeURLField,result);
^
In file included from c:\appdata\local\arduino15\packages\arduino\tools\arm-none-eabi-gcc\4.8.3-2014q1\arm-none-eabi\include\stdlib.h:11:0,
from C:\AppData\Local\Arduino15\packages\arduino\hardware\samd\1.6.17\cores\arduino/Arduino.h:25,
from sketch\20180202-5.ino.cpp:1:
c:\appdata\local\arduino15\packages\arduino\tools\arm-none-eabi-gcc\4.8.3-2014q1\arm-none-eabi\include\string.h:26:8: error: initializing argument 2 of 'char* strcat(char*, const char*)' [-fpermissive]
char *_EXFUN(strcat,(char *__restrict, const char *__restrict));
^
20180202-5:134: error: invalid conversion from 'char*' to 'char' [-fpermissive]
return writeURLField;
^
exit status 1
invalid conversion from 'char' to 'const char*' [-fpermissive]
just needed some time to look at it properly. Should be able to use this method now to break up the URL's I'm trying to send through to the MKR GSM 1400 and get it talking to Thingspeak a bit more nicely than just hard coding the URL's.