feat(eppp_link): Added slave/ppp-server example

components/eppp_link/examples/slave/CMakeLists.txt

@@ -0,0 +1,6 @@
+# The following five lines of boilerplate have to be in your project's
+# CMakeLists in this exact order for cmake to work correctly
+cmake_minimum_required(VERSION 3.16)
+
+include($ENV{IDF_PATH}/tools/cmake/project.cmake)
+project(pppos_slave)

components/eppp_link/examples/slave/README.md

@@ -0,0 +1,7 @@
+
+# Wi-Fi station to PPPoS server
+
+This example demonstrate using NAPT to bring connectivity from WiFi station to PPPoS server.
+
+This example expect a PPPoS client to connect to the server and use the connectivity.
+The client could be a Linux computer with `pppd` service or another microcontroller with PPP client (or another ESP32 with not WiFi interface)

components/eppp_link/examples/slave/main/CMakeLists.txt

@@ -0,0 +1,2 @@
+idf_component_register(SRCS "station_example_main.c"
+                    INCLUDE_DIRS ".")

components/eppp_link/examples/slave/main/Kconfig.projbuild

@@ -0,0 +1,21 @@
+menu "Example Configuration"
+
+    config ESP_WIFI_SSID
+        string "WiFi SSID"
+        default "myssid"
+        help
+            SSID (network name) for the example to connect to.
+
+    config ESP_WIFI_PASSWORD
+        string "WiFi Password"
+        default "mypassword"
+        help
+            WiFi password (WPA or WPA2) for the example to use.
+
+    config ESP_MAXIMUM_RETRY
+        int "Maximum retry"
+        default 5
+        help
+            Set the Maximum retry to avoid station reconnecting to the AP unlimited when the AP is really inexistent.
+
+endmenu

components/eppp_link/examples/slave/main/idf_component.yml

@@ -0,0 +1,4 @@
+dependencies:
+  espressif/eppp_link:
+    version: "*"
+    override_path: "../../.."

components/eppp_link/examples/slave/main/station_example_main.c

@@ -0,0 +1,132 @@
+/*
+ * SPDX-FileCopyrightText: 2023 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Unlicense OR CC0-1.0
+ */
+
+#include <string.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.h"
+#include "esp_log.h"
+#include "nvs_flash.h"
+#include "eppp_link.h"
+
+#include "lwip/err.h"
+#include "lwip/sys.h"
+
+/* FreeRTOS event group to signal when we are connected*/
+static EventGroupHandle_t s_wifi_event_group;
+
+/* The event group allows multiple bits for each event, but we only care about two events:
+ * - we are connected to the AP with an IP
+ * - we failed to connect after the maximum amount of retries */
+#define WIFI_CONNECTED_BIT BIT0
+#define WIFI_FAIL_BIT      BIT1
+
+static const char *TAG = "sta2pppos";
+
+static int s_retry_num = 0;
+
+static void event_handler(void *arg, esp_event_base_t event_base, int32_t event_id, void *event_data)
+{
+    if (event_base == WIFI_EVENT && event_id == WIFI_EVENT_STA_START) {
+        esp_wifi_connect();
+    } else if (event_base == WIFI_EVENT && event_id == WIFI_EVENT_STA_DISCONNECTED) {
+        if (s_retry_num < CONFIG_ESP_MAXIMUM_RETRY) {
+            esp_wifi_connect();
+            s_retry_num++;
+            ESP_LOGI(TAG, "retry to connect to the AP");
+        } else {
+            xEventGroupSetBits(s_wifi_event_group, WIFI_FAIL_BIT);
+        }
+        ESP_LOGI(TAG, "connect to the AP fail");
+    } else if (event_base == IP_EVENT && event_id == IP_EVENT_STA_GOT_IP) {
+        ip_event_got_ip_t *event = (ip_event_got_ip_t *) event_data;
+        ESP_LOGI(TAG, "got ip:" IPSTR, IP2STR(&event->ip_info.ip));
+        s_retry_num = 0;
+        xEventGroupSetBits(s_wifi_event_group, WIFI_CONNECTED_BIT);
+    }
+}
+
+void wifi_init_sta(void)
+{
+    s_wifi_event_group = xEventGroupCreate();
+
+    ESP_ERROR_CHECK(esp_netif_init());
+
+    ESP_ERROR_CHECK(esp_event_loop_create_default());
+    esp_netif_create_default_wifi_sta();
+
+    wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();
+    ESP_ERROR_CHECK(esp_wifi_init(&cfg));
+
+    esp_event_handler_instance_t instance_any_id;
+    esp_event_handler_instance_t instance_got_ip;
+    ESP_ERROR_CHECK(esp_event_handler_instance_register(WIFI_EVENT,
+                    ESP_EVENT_ANY_ID,
+                    &event_handler,
+                    NULL,
+                    &instance_any_id));
+    ESP_ERROR_CHECK(esp_event_handler_instance_register(IP_EVENT,
+                    IP_EVENT_STA_GOT_IP,
+                    &event_handler,
+                    NULL,
+                    &instance_got_ip));
+
+    wifi_config_t wifi_config = {
+        .sta = {
+            .ssid = CONFIG_ESP_WIFI_SSID,
+            .password = CONFIG_ESP_WIFI_PASSWORD,
+        },
+    };
+    ESP_ERROR_CHECK(esp_wifi_set_mode(WIFI_MODE_STA) );
+    ESP_ERROR_CHECK(esp_wifi_set_config(WIFI_IF_STA, &wifi_config) );
+    ESP_ERROR_CHECK(esp_wifi_start() );
+
+    ESP_LOGI(TAG, "wifi_init_sta finished.");
+
+    /* Waiting until either the connection is established (WIFI_CONNECTED_BIT) or connection failed for the maximum
+     * number of re-tries (WIFI_FAIL_BIT). The bits are set by event_handler() (see above) */
+    EventBits_t bits = xEventGroupWaitBits(s_wifi_event_group,
+                                           WIFI_CONNECTED_BIT | WIFI_FAIL_BIT,
+                                           pdFALSE,
+                                           pdFALSE,
+                                           portMAX_DELAY);
+
+    /* xEventGroupWaitBits() returns the bits before the call returned, hence we can test which event actually
+     * happened. */
+    if (bits & WIFI_CONNECTED_BIT) {
+        ESP_LOGI(TAG, "connected to ap SSID:%s password:%s",
+                 CONFIG_ESP_WIFI_SSID, CONFIG_ESP_WIFI_PASSWORD);
+    } else if (bits & WIFI_FAIL_BIT) {
+        ESP_LOGI(TAG, "Failed to connect to SSID:%s, password:%s",
+                 CONFIG_ESP_WIFI_SSID, CONFIG_ESP_WIFI_PASSWORD);
+    } else {
+        ESP_LOGE(TAG, "UNEXPECTED EVENT");
+    }
+}
+
+void app_main(void)
+{
+    //Initialize NVS
+    esp_err_t ret = nvs_flash_init();
+    if (ret == ESP_ERR_NVS_NO_FREE_PAGES || ret == ESP_ERR_NVS_NEW_VERSION_FOUND) {
+        ESP_ERROR_CHECK(nvs_flash_erase());
+        ret = nvs_flash_init();
+    }
+    ESP_ERROR_CHECK(ret);
+
+    ESP_LOGI(TAG, "ESP_WIFI_MODE_STA");
+    wifi_init_sta();
+
+    esp_netif_t *eppp_netif = eppp_listen();
+    if (eppp_netif == NULL) {
+        ESP_LOGE(TAG, "Failed to setup connection");
+        return ;
+    }
+    ESP_ERROR_CHECK(esp_netif_napt_enable(eppp_netif));
+}

components/eppp_link/examples/slave/sdkconfig.defaults

@@ -0,0 +1,8 @@
+CONFIG_UART_ISR_IN_IRAM=y
+CONFIG_LWIP_IP_FORWARD=y
+CONFIG_LWIP_IPV4_NAPT=y
+CONFIG_LWIP_TCPIP_TASK_STACK_SIZE=4096
+CONFIG_LWIP_PPP_SUPPORT=y
+CONFIG_LWIP_PPP_SERVER_SUPPORT=y
+CONFIG_LWIP_PPP_VJ_HEADER_COMPRESSION=n
+CONFIG_EPPP_LINK_DEVICE_SPI=y