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mBed - Google API source code
A few people have asked me to post the source code. Here it is. Even though I have been programming for years in various database and IBM mainframe languages, I've never done much C, so feel free to send me a few tips. I'm not sure why, for example, it works only when ctTime and buffer[21] are declared outside of the subroutine they're used in??

All the libraries used can all be found on the mbed website.

#include "mbed.h"
   #include "DS18B20.h"
   #include "DS18S20.h"
   #include "OneWireDefs.h"
   #include "EthernetNetIf.h"
   #include "HTTPClient.h"
   #include "NTPClient.h"

#define THERMOMETER DS18S20
#define HOSTNAME "mbed"
string calendar = "<<< YOUR CALENDAR PRIVATE ADDRESS >>>";

EthernetNetIf eth(HOSTNAME);
HTTPClient http;
NTPClient ntp;
THERMOMETER device(true, false, false, p21);

DigitalOut led1(LED1, "led1");
DigitalOut led2(LED2, "led2");
DigitalOut led3(LED3, "led3");
DigitalOut led4(LED4, "led4");

DigitalOut heater(p10);
time_t ctTime;
char buffer[21];
int targetTemp = 0;

string getURL() {
    char url[256];
    char endTime[21];
    char startTime[21];
    ctTime = time(NULL);
    strftime(buffer, 20, "%Y-%m-%dT%H:%M:00Z", localtime(&ctTime));
    strcpy(startTime,buffer);
    ctTime = time(NULL)+60;
    strftime(buffer, 20, "%Y-%m-%dT%H:%M:00Z", localtime(&ctTime));
    strcpy(endTime,buffer);       
    //printf("start %s\n",startTime);
    //printf("end   %s\n",endTime);
    sprintf(url, "%s?start-min=%s&start-max=%s", calendar, startTime, endTime);
    //printf("url   %s\n",url);
    return url;
}

string getPage(char url[256]) {
    printf("\nQuery Google API... \n");
    HTTPText txt("text/html",5000);
    HTTPResult r = http.get(url, &txt);
   
    if (r==HTTP_OK) {
       printf("Result Ok\n");
       led2 = 0;
       return txt.gets();
    } else {
       printf("Error %d\n",r);
       led2 = 1;
       return "FAIL";
    }
}

void getAPI() {
    string testres;
    string results;
    char to[3];
    char url[256];
    strcpy(url,(char*)getURL().c_str());
    results = getPage(url);
    //printf("results API %s\n",results);
    
    if (results == "FAIL") {
       printf("%s\n","Bad Result");
       // Make no changes to the target temperature
    } else {
       testres = strstr(results.c_str(),"<title type='html'>");
       //printf("\n\n\n%s\n",testres);
       if (testres == "") {
          // no temperature set for this time
          printf("%s\n","No calendar entry for this time");
          targetTemp = 0;
          led3 = 0;
       } else {
          // grab the temperature (this assumes I've entered a 2 digit int in the event title)
          strncpy(to, testres.c_str()+19, 2);
          printf("result: %s\n", to);
          targetTemp = atoi(to);
          led3 = 1;
       }
    }
}

void getNTP() {
    ctTime = time(NULL);
    printf("Current time is (UTC): %d %s\n", ctTime, ctime(&ctTime));
    printf("NTP setTime...\n");
    Host server(IpAddr(), 123, "pool.ntp.org");
    printf("Result : %d\n", ntp.setTime(server));
    ctTime = time(NULL);
    printf("Time is now (UTC): %d %s\n", ctTime, ctime(&ctTime));
}

void checkTemperature() {
    float temp = device.readTemperature();
    if (temp > (targetTemp+0.5)) {
       heater = 0;
       led4 = 0;
    } 
    if (temp < targetTemp) {
       heater = 1;
       led4 = 1;
    }
}

int main() {
    EthernetErr ethErr;
    int count = 0;
    do {
        printf("Setting up %d...\n", ++count);
        ethErr = eth.setup();
        if (ethErr) printf("Timeout\n", ethErr);
    } while (ethErr != ETH_OK);

printf("Connected OK\n");
    const char* hwAddr = eth.getHwAddr();
    printf("HW address : %02x:%02x:%02x:%02x:%02x:%02x\n",
           hwAddr[0], hwAddr[1], hwAddr[2],
           hwAddr[3], hwAddr[4], hwAddr[5]);

IpAddr ethIp = eth.getIp();
    printf("IP address : %d.%d.%d.%d\n", ethIp[0], ethIp[1], ethIp[2], ethIp[3]);
    printf("Check router DHCP table for name : %s\n", eth.getHostname());

getNTP();
    getAPI();
    
    Timer pollTemp;
    pollTemp.start();
    Timer pollAPI;
    pollAPI.start();
    Timer pollNTP;
    pollNTP.start();
    Timer lookAlive;
    lookAlive.start();
    
    while (true) {
        if (lookAlive.read() > 1) {
           led1 = !led1;
           lookAlive.start();
        }
        if (pollTemp.read() > 10) {
            checkTemperature();
            pollTemp.start();
        }
        if (pollAPI.read() > 30) {
            getAPI();
            printf("Target Temp: %i\n",targetTemp);
            pollAPI.start();
        }
        if (pollNTP.read() > 21000) {
            pollNTP.start();
            getNTP();
        }
    }
}

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