diff --git a/central_backend/src/server/devices_api/mgmt_controller.rs b/central_backend/src/server/devices_api/mgmt_controller.rs
index 9fac4eb..3c201eb 100644
--- a/central_backend/src/server/devices_api/mgmt_controller.rs
+++ b/central_backend/src/server/devices_api/mgmt_controller.rs
@@ -2,6 +2,7 @@ use crate::app_config::AppConfig;
 use crate::crypto::pki;
 use crate::devices::device::{DeviceId, DeviceInfo};
 use crate::energy::energy_actor;
+use crate::energy::energy_actor::RelaySyncStatus;
 use crate::server::custom_error::HttpResult;
 use crate::server::WebEnergyActor;
 use actix_web::{web, HttpResponse};
@@ -138,6 +139,11 @@ struct Claims {
     info: DeviceInfo,
 }
 
+#[derive(serde::Serialize)]
+struct SyncResult {
+    relays: Vec<RelaySyncStatus>,
+}
+
 /// Synchronize device
 pub async fn sync_device(body: web::Json<SyncRequest>, actor: WebEnergyActor) -> HttpResult {
     // First, we need to extract device kid from query
@@ -199,9 +205,9 @@ pub async fn sync_device(body: web::Json<SyncRequest>, actor: WebEnergyActor) ->
         }
     };
 
-    let res = actor
+    let relays = actor
         .send(energy_actor::SynchronizeDevice(device.id, c.claims.info))
         .await??;
 
-    Ok(HttpResponse::Ok().json(res))
+    Ok(HttpResponse::Ok().json(SyncResult { relays }))
 }
diff --git a/central_backend/src/utils/mod.rs b/central_backend/src/utils/mod.rs
index 5ccc580..40a5909 100644
--- a/central_backend/src/utils/mod.rs
+++ b/central_backend/src/utils/mod.rs
@@ -1,3 +1,3 @@
 pub mod files_utils;
- pub mod math_utils;
+pub mod math_utils;
 pub mod time_utils;
diff --git a/esp32_device/.vscode/settings.json b/esp32_device/.vscode/settings.json
index 1111ea0..0bf7131 100644
--- a/esp32_device/.vscode/settings.json
+++ b/esp32_device/.vscode/settings.json
@@ -49,6 +49,7 @@
     "regex": "c",
     "stdlib.h": "c",
     "secure_api.h": "c",
-    "jwt.h": "c"
+    "jwt.h": "c",
+    "sync_response.h": "c"
   }
 }
diff --git a/esp32_device/main/CMakeLists.txt b/esp32_device/main/CMakeLists.txt
index f7bdb83..a7b6504 100755
--- a/esp32_device/main/CMakeLists.txt
+++ b/esp32_device/main/CMakeLists.txt
@@ -1,4 +1,4 @@
-idf_component_register(SRCS "jwt.c" "secure_api.c" "http_client.c" "ethernet.c" "unsecure_api.c" "system.c" "crypto.c" "random.c" "storage.c" "main.c"
+idf_component_register(SRCS "sync_response.c" "jwt.c" "secure_api.c" "http_client.c" "ethernet.c" "unsecure_api.c" "system.c" "crypto.c" "random.c" "storage.c" "main.c"
                         "dev_name.c"
                     INCLUDE_DIRS ".")
 
diff --git a/esp32_device/main/constants.h b/esp32_device/main/constants.h
index 9304bcf..eb0f81a 100644
--- a/esp32_device/main/constants.h
+++ b/esp32_device/main/constants.h
@@ -43,4 +43,9 @@
 /**
  * Secure origin len
  */
-#define SEC_ORIG_LEN 255
\ No newline at end of file
+#define SEC_ORIG_LEN 255
+
+/**
+ * Interval of time (in seconds) between two synchronisations
+ */
+#define SYNC_TIME_INTERVAL 5
\ No newline at end of file
diff --git a/esp32_device/main/main.c b/esp32_device/main/main.c
index 9caf544..4ca3965 100755
--- a/esp32_device/main/main.c
+++ b/esp32_device/main/main.c
@@ -21,6 +21,8 @@ void app_main(void)
 
     ESP_LOGI(TAG, "SolarEnergy WT32-ETH01 device");
 
+    // TODO : turn off all relays
+
     // Initialize storage
     if (storage_init() == false)
     {
@@ -167,22 +169,40 @@ void app_main(void)
     // Main loop
     ESP_LOGI(TAG, "Starting main loop");
 
-    // TODO : implement more properly
+    size_t fails = 0;
     while (true)
     {
-        if (!secure_api_sync_device())
+        sync_response *res = secure_api_sync_device();
+        if (!res)
         {
+            fails += 1;
             ESP_LOGE(TAG, "Failed to synchronise device!");
-        }
-        else
-        {
-            ESP_LOGI(TAG, "Successfully synchronised device!");
+
+            // Safely turn off all relays after a given number of failures
+            if (fails > 5)
+            {
+                ESP_LOGE(TAG, "Many failures, will stop all relays...");
+                // TODO : turn off all relays
+            }
+
+            // Restart the card after too much failures
+            if (fails > 10)
+            {
+                ESP_LOGE(TAG, "Too many failures, will try to reboot in 3 secs...");
+                system_sleep(3);
+                reboot();
+            }
+
+            system_sleep(SYNC_TIME_INTERVAL);
+            continue;
         }
 
-        system_sleep(10);
+        // TODO : apply sync
+        sync_response_print(res);
+
+        sync_response_free(res);
+        system_sleep(SYNC_TIME_INTERVAL);
     }
 
-    system_sleep(120);
-
     reboot();
 }
diff --git a/esp32_device/main/secure_api.c b/esp32_device/main/secure_api.c
index 323a3e8..d58733e 100644
--- a/esp32_device/main/secure_api.c
+++ b/esp32_device/main/secure_api.c
@@ -148,16 +148,16 @@ int secure_api_enroll_device()
     free(csr);
 
     char *body = cJSON_PrintUnformatted(obj);
+    cJSON_Delete(obj);
+
     if (!body)
     {
         ESP_LOGE(TAG, "Failed to generate JSON body!");
-        cJSON_Delete(obj);
         return 1;
     }
 
     char *res = process_secure_request("/devices_api/mgmt/enroll", body);
 
-    cJSON_Delete(obj);
     free(body);
 
     if (res == NULL)
@@ -195,7 +195,7 @@ char *secure_api_get_dev_certificate()
     return res;
 }
 
-void *secure_api_sync_device()
+sync_response *secure_api_sync_device()
 {
     cJSON *obj = cJSON_CreateObject();
     if (!obj)
@@ -215,10 +215,53 @@ void *secure_api_sync_device()
         return NULL;
     }
 
-    printf("JWT: %s\n", encoded_req);
+    // Prepare request body
+    cJSON *json_body = cJSON_CreateObject();
+    if (!json_body)
+    {
+        ESP_LOGE(TAG, "Failed to allocated memory to store sync request body!");
+        free(encoded_req);
+        return NULL;
+    }
+    cJSON_AddStringToObject(json_body, "payload", encoded_req);
     free(encoded_req);
 
-    // TODO : replace
-    printf("here implement sync device logic\n");
-    return NULL;
+    char *body = cJSON_PrintUnformatted(json_body);
+    cJSON_Delete(json_body);
+
+    if (!body)
+    {
+        ESP_LOGE(TAG, "Failed to allocated memory to store encoded sync request body!");
+        return NULL;
+    }
+
+    // Send request
+    char *res = process_secure_request("/devices_api/mgmt/sync", body);
+    if (res == NULL)
+    {
+        ESP_LOGE(TAG, "Sync request failed!");
+        return NULL;
+    }
+
+    // Parse response
+    cJSON *states = cJSON_Parse(res);
+    free(res);
+
+    if (!states)
+    {
+        ESP_LOGE(TAG, "Failed to decode sync response from server!");
+        return NULL;
+    }
+
+    sync_response *sync_res = sync_response_parse(states);
+
+    cJSON_Delete(states);
+
+    if (!sync_res)
+    {
+        ESP_LOGE(TAG, "Failed to parse sync response from server!");
+        return NULL;
+    }
+
+    return sync_res;
 }
\ No newline at end of file
diff --git a/esp32_device/main/secure_api.h b/esp32_device/main/secure_api.h
index 4d486f2..1a5f71f 100644
--- a/esp32_device/main/secure_api.h
+++ b/esp32_device/main/secure_api.h
@@ -2,6 +2,11 @@
  * Secure API functions
  */
 
+#include <stddef.h>
+#include <stdbool.h>
+
+#include "sync_response.h"
+
 #pragma once
 
 #ifdef __cplusplus
@@ -45,7 +50,7 @@ extern "C"
      *
      * Returns NULL in case of failure
      */
-    void *secure_api_sync_device();
+    sync_response *secure_api_sync_device();
 
 #ifdef __cplusplus
 }
diff --git a/esp32_device/main/sync_response.c b/esp32_device/main/sync_response.c
new file mode 100644
index 0000000..7ba3690
--- /dev/null
+++ b/esp32_device/main/sync_response.c
@@ -0,0 +1,63 @@
+#include "sync_response.h"
+
+#include <stdlib.h>
+#include <esp_log.h>
+
+const static char *TAG = "sync_response";
+
+sync_response *sync_response_parse(cJSON *res)
+{
+    cJSON *relays_json = cJSON_GetObjectItem(res, "relays");
+    if (relays_json == NULL)
+    {
+        ESP_LOGE(TAG, "Missing relays status in sync response!");
+        return NULL;
+    }
+
+    int relays_size = cJSON_GetArraySize(relays_json);
+    sync_response *sync_res = calloc(1, sizeof(sync_response) + relays_size * sizeof(bool));
+
+    if (!sync_res)
+    {
+        ESP_LOGE(TAG, "Failed to allocate memory to store synchronization response!");
+        return NULL;
+    }
+
+    sync_res->len = relays_size;
+
+    for (int i = 0; i < sync_res->len; i++)
+    {
+        sync_res->relays[i] = false;
+
+        cJSON *item = cJSON_GetArrayItem(relays_json, i);
+        assert(item != NULL);
+        cJSON *enabled = cJSON_GetObjectItem(item, "enabled");
+
+        if (enabled == NULL)
+        {
+            ESP_LOGE(TAG, "At least a relay is missing the enabled field. Assuming false.");
+            continue;
+        }
+
+        if (cJSON_IsTrue(enabled))
+        {
+            sync_res->relays[i] = true;
+        }
+    }
+
+    return sync_res;
+}
+
+void sync_response_print(sync_response *res)
+{
+    ESP_LOGI(TAG, " === sync response begin === ");
+    for (size_t i = 0; i < res->len; i++)
+        ESP_LOGI(TAG, "Relay[%d]=%s", i, res->relays[i] ? "ON" : "off");
+    ESP_LOGI(TAG, " === sync response end === ");
+}
+
+void sync_response_free(sync_response *res)
+{
+    if (res != NULL)
+        free(res);
+}
\ No newline at end of file
diff --git a/esp32_device/main/sync_response.h b/esp32_device/main/sync_response.h
new file mode 100644
index 0000000..b4a81db
--- /dev/null
+++ b/esp32_device/main/sync_response.h
@@ -0,0 +1,39 @@
+/**
+ * Synchronisation response
+ */
+
+#pragma once
+
+#include <stddef.h>
+#include <stdbool.h>
+#include <cJSON.h>
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+    typedef struct sync_response
+    {
+        size_t len;
+        bool relays[];
+    } sync_response;
+
+    /**
+     * Decode synchronize response from server
+     */
+    sync_response *sync_response_parse(cJSON *res);
+
+    /**
+     * Print synchronize reponse content
+     */
+    void sync_response_print(sync_response *res);
+
+    /**
+     * Free memory allocated for synchronize response
+     */
+    void sync_response_free(sync_response *res);
+
+#ifdef __cplusplus
+}
+#endif