CC3220SF: Certificate error MQTT Google IoT Core

Hi all,

I'm trying to connect to the Google iot Core with MQTT but so far it's not working.

I have verified that the needed credentials such as the clientid and password (in this case the JWT token needed for google's iot core) are correct with a local mqtt client. I was able to connect to my registered device and able to publish messages.

However when I try to connect it with the CC3220SF I get the following error message on the serial terminal: 

I checked the certificate and verified that it actually is a GlobalSign certificate so I'm really confused here. This is the most common error I get while occasionally also getting -468, -458, -457 or -2005 depending on the root certificate that I upload. All the root certificates that I have tried I have downloaded directly from google, either from their certificates repository (pki.goog/repository/) or from their MQTT-bridge example page cloud.google.com/iot/docs/how-tos/mqtt-bridge. 

I upload them as such via Uniflash :

I followed the empty MQTT example from the SDK and was able to connect to the eclipse broker with a secured connection. I expanded the code and added the needed credentials for the google iot core but I must be doing something wrong as I'm not able to connect to their MQTT broker.

Here is part of my code :

 #define ClientId                    "projects/myProjectId/locations/europe-west1/registries/myRegistry/devices/qdevice"
 #define MQTT_CLIENT_PASSWORD        "myJWTtoken"
 #define MQTT_CLIENT_USERNAME        "unused"
 #define MQTT_CLIENT_KEEPALIVE       60
 #define MQTT_CLIENT_CLEAN_CONNECT   true
 #define MQTT_CLIENT_MQTT_V3_1       false
 #define MQTT_CLIENT_BLOCKING_SEND   true
 char *MQTTClient_secureFiles[1] = {"gsr2.pem"};

 #define MQTT_CONNECTION_FLAGS       MQTTCLIENT_NETCONN_URL | MQTTCLIENT_NETCONN_SEC
 #define MQTT_CONNECTION_ADDRESS     "mqtt.googleapis.com"
 #define MQTT_CONNECTION_PORT_NUMBER  8883

 #define SL_TASKSTACKSIZE            2048
 #define SPAWN_TASK_PRIORITY         9

 MQTT_IF_InitParams_t mqttInitParams =
 {
      MQTT_MODULE_TASK_STACK_SIZE,   // stack size for mqtt module
      MQTT_MODULE_TASK_PRIORITY      // thread priority for MQTT
 };

 MQTT_IF_ClientParams_t mqttClientParams =
 {
      ClientId,                  // client ID
      MQTT_CLIENT_USERNAME,      // user name
      MQTT_CLIENT_PASSWORD,      // password
      MQTT_CLIENT_KEEPALIVE,     // keep-alive time
      MQTT_CLIENT_CLEAN_CONNECT, // clean connect flag
      MQTT_CLIENT_MQTT_V3_1,     // true = 3.1, false = 3.1.1
      MQTT_CLIENT_BLOCKING_SEND, // blocking send flag
 };

 MQTTClient_ConnParams mqttConnParams =
 {
     MQTT_CONNECTION_FLAGS,                  // connection flags
     MQTT_CONNECTION_ADDRESS,                // server address
     MQTT_CONNECTION_PORT_NUMBER,            // port number of MQTT server
     SLNETSOCK_SEC_METHOD_TLSV1_2,     // method for secure socket
     SLNETSOCK_SEC_CIPHER_FULL_LIST,         // cipher for secure socket
     1,                                      // number of files for secure connection
     MQTTClient_secureFiles                  // secure files
 };


/* When MQTT_if_handler is called use is expected to provide event callback.
 * This callback will be used by the MQTT client module to notify the main application when certain MQTT events have occured (e.g. connect, disconnect, etc) */
 void MQTT_EventCallback(int32_t event)
 {
     switch(event){
         case MQTT_EVENT_CONNACK:
         {
             LOG_INFO("MQTT_EVENT_CONNACK\r\n");
             break;
         }
         case MQTT_EVENT_CLIENT_DISCONNECT:
         {
             LOG_INFO("MQTT_EVENT_CLIENT_DISCONNECT\r\n");
             break;
         }
         case MQTT_EVENT_SERVER_DISCONNECT:
         {
             LOG_INFO("MQTT_EVENT_SERVER_DISCONNECT\r\n");
             break;
         }
         case MQTT_EVENT_DESTROY:
         {
             LOG_INFO("MQTT_EVENT_DESTROY\r\n");
             break;
         }
         default:
         {
             LOG_INFO("Unknown MQTT event\r\n");
             break;
         }
     }
 }

 /* WiFi initialiser */

 int WifiInit(){
     int32_t ret;
     SlWlanSecParams_t security_params;
     pthread_t spawn_thread = (pthread_t) NULL;
     pthread_attr_t pattrs_spawn;
     struct sched_param pri_param;

     pthread_attr_init(&pattrs_spawn);
     pri_param.sched_priority = SPAWN_TASK_PRIORITY;
     ret = pthread_attr_setschedparam(&pattrs_spawn, &pri_param);
     ret |= pthread_attr_setstacksize(&pattrs_spawn, SL_TASKSTACKSIZE);
     ret |= pthread_attr_setdetachstate(&pattrs_spawn, PTHREAD_CREATE_DETACHED);
     ret = pthread_create(&spawn_thread, &pattrs_spawn, sl_Task, NULL);
     if(ret != 0){
         LOG_ERROR("could not create simplelink task\n\r");
         while(1);
     }

     Network_IF_ResetMCUStateMachine();

     Network_IF_DeInitDriver();

     ret = Network_IF_InitDriver(ROLE_STA);
     if(ret < 0){
         LOG_ERROR("Failed to start SimpleLink Device\n\r");
         while(1);
     }

    // SetClientIdNamefromMacAddress();

     security_params.Key = (signed char*)SECURITY_KEY;
     security_params.KeyLen = strlen(SECURITY_KEY);
     security_params.Type = SECURITY_TYPE;

     ret = Network_IF_ConnectAP(SSID_NAME, security_params);
     if(ret < 0){
         LOG_ERROR("Connection to an AP failed\n\r");
     }
     else{
         ret = sl_WlanProfileAdd((signed char*)SSID_NAME, strlen(SSID_NAME), 0, &security_params, NULL, 7, 0);
         if(ret < 0){
             LOG_ERROR("failed to add profile %s\r\n", SSID_NAME);
         }
         else{
             LOG_INFO("profile added %s\r\n", SSID_NAME);
         }
     }

     return ret;
 }

 void MQTTDemo(char* topic, char* payload, uint8_t qos)
 {
     LOG_INFO("TOPIC: %s PAYLOAD: %s QOS: %d\r\n", topic, payload, qos);
}

/*
 *  ======== mainThread ========
 */
void *mainThread(void *arg0)
{
    /* 1 second delay */
    uint32_t time = 1;

    /* MQTT variables */
    int32_t ret;
    UART_Handle uartHandle;
    MQTTClient_Handle mqttClientHandle;

    GPIO_init();
    SPI_init();

    /* Open UART instance to enable application printing */
    uartHandle = InitTerm();
    UART_control(uartHandle, UART_CMD_RXDISABLE, NULL);

    /* Initialize the IP network services layer for the MQTT client module */
    ret = ti_net_SlNet_initConfig();
    if(0 != ret)
    {
        LOG_ERROR("Failed to initialize SlNetSock\n\r");
    }

    /* Call WifiInit() to start the network processor and connect to an Access Point */
    ret = WifiInit();
    if(ret < 0){
        while(1);
    }

    setTime();

    /* Initialize MQTT client module */
    ret = MQTT_IF_Init(mqttInitParams);
    if(ret < 0){
        while(1);
    }

    ret = MQTT_IF_Subscribe(mqttClientHandle, "/devices/mydevice/events", MQTT_QOS_1, MQTTDemo); //Google doesnt support QOS 2
    if(ret < 0){
        while(1);
    }
    else{
        LOG_INFO("Subscribed to all topics successfully\r\n");
    }

    /* Connect MQTT broker and register event call back */
    mqttClientHandle = MQTT_IF_Connect(mqttClientParams, mqttConnParams, MQTT_EventCallback);
    if(mqttClientHandle < 0){
        while(1);
    }

    while (1) {
        sleep(time);
        MQTT_IF_Publish(mqttClientHandle,
                        "/devices/qdevice/events",
                        "hello\r\n",
                        strlen("hello\r\n"),
                        MQTT_QOS_0);
    }
}