Added channel, ssid scan (esp8266#4636)

* Added channel, ssid scan

Overloaded scanNetworks so scan can occur on a single channel and/or for a particular ssid.

* Added parameters to scanNetworks

channel number and ssid have been added as optional parameters to the orginal scanNetworks()

libraries/ESP8266WiFi/src/ESP8266WiFiScan.cpp

@@ -64,9 +64,11 @@ std::function<void(int)> ESP8266WiFiScanClass::_onComplete;
  * Start scan WiFi networks available
  * @param async run in async mode
  * @param show_hidden show hidden networks
+ * @param channel scan only this channel (0 for all channels)
+ * @param ssid* scan for only this ssid (NULL for all ssid's)
  * @return Number of discovered networks
  */
-int8_t ESP8266WiFiScanClass::scanNetworks(bool async, bool show_hidden) {
+int8_t ESP8266WiFiScanClass::scanNetworks(bool async, bool show_hidden, uint8 channel, uint8* ssid) {
  if(ESP8266WiFiScanClass::_scanStarted) {
  return WIFI_SCAN_RUNNING;
  }
@@ -84,6 +86,8 @@ int8_t ESP8266WiFiScanClass::scanNetworks(bool async, bool show_hidden) {
 
  struct scan_config config;
  memset(&config, 0, sizeof(config));
+ config.ssid = ssid;
+ config.channel = channel;
  config.show_hidden = show_hidden;
  if(wifi_station_scan(&config, reinterpret_cast<scan_done_cb_t>(&ESP8266WiFiScanClass::_scanDone))) {
  ESP8266WiFiScanClass::_scanComplete = false;

libraries/ESP8266WiFi/src/ESP8266WiFiScan.h

@@ -34,7 +34,7 @@ class ESP8266WiFiScanClass {
 
  public:
 
- int8_t scanNetworks(bool async = false, bool show_hidden = false);
+ int8_t scanNetworks(bool async = false, bool show_hidden = false, uint8 channel = 0, uint8* ssid = NULL);
  void scanNetworksAsync(std::function<void(int)> onComplete, bool show_hidden = false);
 
  int8_t scanComplete();