esp8266/modnetwork: Implement WLAN.status('rssi') for STA interface.

This will return the RSSI of the AP that the STA is connected to.

docs/library/network.rst

@@ -383,10 +383,11 @@ parameter should be `id`.
             * 0 -- visible
             * 1 -- hidden
 
-    .. method:: wlan.status()
+    .. method:: wlan.status([param])
 
         Return the current status of the wireless connection.
 
+        When called with no argument the return value describes the network link status.
         The possible statuses are defined as constants:
 
             * ``STAT_IDLE`` -- no connection and no activity,
@@ -396,6 +397,9 @@ parameter should be `id`.
             * ``STAT_CONNECT_FAIL`` -- failed due to other problems,
             * ``STAT_GOT_IP`` -- connection successful.
 
+        When called with one argument *param* should be a string naming the status
+        parameter to retrieve.  Supported parameters in WiFI STA mode are: ``'rssi'``.
+
     .. method:: wlan.isconnected()
 
         In case of STA mode, returns ``True`` if connected to a WiFi access

ports/esp8266/modnetwork.c

@@ -150,14 +150,26 @@ STATIC mp_obj_t esp_disconnect(mp_obj_t self_in) {
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(esp_disconnect_obj, esp_disconnect);
 
-STATIC mp_obj_t esp_status(mp_obj_t self_in) {
-    wlan_if_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    if (self->if_id == STATION_IF) {
-        return MP_OBJ_NEW_SMALL_INT(wifi_station_get_connect_status());
+STATIC mp_obj_t esp_status(size_t n_args, const mp_obj_t *args) {
+    wlan_if_obj_t *self = MP_OBJ_TO_PTR(args[0]);
+    if (n_args == 1) {
+        // Get link status
+        if (self->if_id == STATION_IF) {
+            return MP_OBJ_NEW_SMALL_INT(wifi_station_get_connect_status());
+        }
+        return MP_OBJ_NEW_SMALL_INT(-1);
+    } else {
+        // Get specific status parameter
+        switch (mp_obj_str_get_qstr(args[1])) {
+            case MP_QSTR_rssi:
+                if (self->if_id == STATION_IF) {
+                    return MP_OBJ_NEW_SMALL_INT(wifi_station_get_rssi());
+                }
+        }
+        mp_raise_ValueError("unknown status param");
     }
-    return MP_OBJ_NEW_SMALL_INT(-1);
 }
-STATIC MP_DEFINE_CONST_FUN_OBJ_1(esp_status_obj, esp_status);
+STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(esp_status_obj, 1, 2, esp_status);
 
 STATIC mp_obj_t *esp_scan_list = NULL;