Merge branch 'feature/refactor_lwip_sntp_example' into 'master'

refactor(sntp): add lwip sntp example

See merge request sdk/ESP8266_RTOS_SDK!496

examples/protocols/sntp/Makefile

@@ -0,0 +1,9 @@
+#
+# This is a project Makefile. It is assumed the directory this Makefile resides in is a
+# project subdirectory.
+#
+
+PROJECT_NAME := sntp
+
+include $(IDF_PATH)/make/project.mk
+

examples/protocols/sntp/README.md

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+# Example: using LwIP SNTP module and time functions
+
+This example demonstrates the use of LwIP SNTP module to obtain time from Internet servers. See the README.md file in the upper level 'examples' directory for more information about examples.
+
+## Obtaining time using LwIP SNTP module
+
+ESP8266 connects to WiFi and obtains time using SNTP.
+See `initialize_sntp` function for details.
+
+## Working with time
+
+To get current time, [`gettimeofday`](http://man7.org/linux/man-pages/man2/gettimeofday.2.html) function may be used. Additionally the following [standard C library functions](https://en.cppreference.com/w/cpp/header/ctime) can be used to obtain time and manipulate it:
+
+	gettimeofday
+	time
+	asctime
+	clock
+	ctime
+	difftime
+	gmtime
+	localtime
+	mktime
+	strftime
+
+To set time, [`settimeofday`](http://man7.org/linux/man-pages/man2/settimeofday.2.html) POSIX function can be used. It is used internally in LwIP SNTP library to set current time when response from NTP server is received.
+
+## Timezones
+
+To set local timezone, use [`setenv`](http://man7.org/linux/man-pages/man3/setenv.3.html) and [`tzset`](http://man7.org/linux/man-pages/man3/tzset.3.html) POSIX functions. First, call `setenv` to set `TZ` environment variable to the correct value depending on device location. Format of the time string is described in [libc documentation](https://www.gnu.org/software/libc/manual/html_node/TZ-Variable.html). Next, call `tzset` to update C library runtime data for the new time zone. Once these steps are done, `localtime` function will return correct local time, taking time zone offset and daylight saving time into account.

examples/protocols/sntp/main/Kconfig.projbuild

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+menu "Example Configuration"
+
+config WIFI_SSID
+    string "WiFi SSID"
+    default "myssid"
+    help
+        SSID (network name) for the example to connect to.
+
+config WIFI_PASSWORD
+    string "WiFi Password"
+    default "mypassword"
+    help
+        WiFi password (WPA or WPA2) for the example to use.
+
+        Can be left blank if the network has no security set.
+
+endmenu

examples/protocols/sntp/main/component.mk

@@ -0,0 +1,4 @@
+#
+# "main" pseudo-component makefile.
+#
+# (Uses default behaviour of compiling all source files in directory, adding 'include' to include path.)

examples/protocols/sntp/main/sntp_example_main.c

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+/* LwIP SNTP example
+
+   This example code is in the Public Domain (or CC0 licensed, at your option.)
+
+   Unless required by applicable law or agreed to in writing, this
+   software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
+   CONDITIONS OF ANY KIND, either express or implied.
+*/
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
+#include "freertos/event_groups.h"
+
+#include "esp_system.h"
+#include "esp_wifi.h"
+#include "esp_event_loop.h"
+#include "esp_log.h"
+
+#include "nvs_flash.h"
+
+#include "lwip/apps/sntp.h"
+
+/* The examples use simple WiFi configuration that you can set via
+   'make menuconfig'.
+
+   If you'd rather not, just change the below entries to strings with
+   the config you want - ie #define EXAMPLE_WIFI_SSID "mywifissid"
+*/
+#define EXAMPLE_WIFI_SSID CONFIG_WIFI_SSID
+#define EXAMPLE_WIFI_PASS CONFIG_WIFI_PASSWORD
+
+/* FreeRTOS event group to signal when we are connected & ready to make a request */
+static EventGroupHandle_t wifi_event_group;
+
+/* The event group allows multiple bits for each event,
+   but we only care about one event - are we connected
+   to the AP with an IP? */
+const int CONNECTED_BIT = BIT0;
+
+static const char *TAG = "sntp_example";
+
+static void initialize_sntp(void)
+{
+    ESP_LOGI(TAG, "Initializing SNTP");
+    sntp_setoperatingmode(SNTP_OPMODE_POLL);
+    sntp_setservername(0, "pool.ntp.org");
+    sntp_init();
+}
+
+static void obtain_time(void)
+{
+    xEventGroupWaitBits(wifi_event_group, CONNECTED_BIT,
+                        false, true, portMAX_DELAY);
+    initialize_sntp();
+
+    // wait for time to be set
+    time_t now = 0;
+    struct tm timeinfo = { 0 };
+    int retry = 0;
+    const int retry_count = 10;
+
+    while (timeinfo.tm_year < (2016 - 1900) && ++retry < retry_count) {
+        ESP_LOGI(TAG, "Waiting for system time to be set... (%d/%d)", retry, retry_count);
+        vTaskDelay(2000 / portTICK_PERIOD_MS);
+        time(&now);
+        localtime_r(&now, &timeinfo);
+    }
+}
+
+static esp_err_t event_handler(void *ctx, system_event_t *event)
+{
+    switch (event->event_id) {
+        case SYSTEM_EVENT_STA_START:
+            esp_wifi_connect();
+            break;
+
+        case SYSTEM_EVENT_STA_GOT_IP:
+            xEventGroupSetBits(wifi_event_group, CONNECTED_BIT);
+            break;
+
+        case SYSTEM_EVENT_STA_DISCONNECTED:
+            /* This is a workaround as ESP8266 WiFi libs don't currently
+               auto-reassociate. */
+            esp_wifi_connect();
+            xEventGroupClearBits(wifi_event_group, CONNECTED_BIT);
+            break;
+
+        default:
+            break;
+    }
+
+    return ESP_OK;
+}
+
+static void sntp_example_task(void *arg)
+{
+    time_t now;
+    struct tm timeinfo;
+    char strftime_buf[64];
+
+    time(&now);
+    localtime_r(&now, &timeinfo);
+
+    // Is time set? If not, tm_year will be (1970 - 1900).
+    if (timeinfo.tm_year < (2016 - 1900)) {
+        ESP_LOGI(TAG, "Time is not set yet. Connecting to WiFi and getting time over NTP.");
+        obtain_time();
+    }
+
+    // Set timezone to Eastern Standard Time and print local time
+    // setenv("TZ", "EST5EDT,M3.2.0/2,M11.1.0", 1);
+    // tzset();
+
+    // Set timezone to China Standard Time
+    setenv("TZ", "CST-8", 1);
+    tzset();
+
+    while (1) {
+        // update 'now' variable with current time
+        time(&now);
+        localtime_r(&now, &timeinfo);
+
+        if (timeinfo.tm_year < (2016 - 1900)) {
+            ESP_LOGE(TAG, "The current date/time error");
+        } else {
+            strftime(strftime_buf, sizeof(strftime_buf), "%c", &timeinfo);
+            ESP_LOGI(TAG, "The current date/time in Shanghai is: %s", strftime_buf);
+        }
+
+        ESP_LOGI(TAG, "Free heap size: %d\n", esp_get_free_heap_size());
+        vTaskDelay(1000 / portTICK_RATE_MS);
+    }
+}
+
+static void initialise_wifi(void)
+{
+    tcpip_adapter_init();
+    wifi_event_group = xEventGroupCreate();
+    ESP_ERROR_CHECK(esp_event_loop_init(event_handler, NULL));
+    wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();
+    ESP_ERROR_CHECK(esp_wifi_init(&cfg));
+    ESP_ERROR_CHECK(esp_wifi_set_storage(WIFI_STORAGE_RAM));
+    wifi_config_t wifi_config = {
+        .sta = {
+            .ssid = EXAMPLE_WIFI_SSID,
+            .password = EXAMPLE_WIFI_PASS,
+        },
+    };
+    ESP_LOGI(TAG, "Setting WiFi configuration SSID %s...", wifi_config.sta.ssid);
+    ESP_ERROR_CHECK(esp_wifi_set_mode(WIFI_MODE_STA));
+    ESP_ERROR_CHECK(esp_wifi_set_config(ESP_IF_WIFI_STA, &wifi_config));
+    ESP_ERROR_CHECK(esp_wifi_start());
+}
+
+void app_main()
+{
+    //Initialize NVS
+    esp_err_t ret = nvs_flash_init();
+
+    if (ret == ESP_ERR_NVS_NO_FREE_PAGES) {
+        ESP_ERROR_CHECK(nvs_flash_erase());
+        ret = nvs_flash_init();
+    }
+
+    ESP_ERROR_CHECK(ret);
+
+    initialise_wifi();
+
+    // SNTP service uses LwIP, please allocate large stack space.
+    xTaskCreate(sntp_example_task, "sntp_example_task", 2048, NULL, 10, NULL);
+}