Hi there,
I am happy to share my solution, not as a complete sketch but with two procedures that are useful. There are some #definitions needed which I hope speak for themselves.
connect2nearestAP does hat it says: scanning the network for all available SSIDs on all APs (the list is fortunately sorted from stronest to weakest) and connects to the first/strongest with matching SSID.
checkWiFi is helpful if the ESP is moving around and the nearest AP is changing. This routine should be called on a regular basis and/or if highest thruput is needed (e.g. you want to send an eMail with attachments). This routine checks if the strengths is above a certain tresold - if not, it calls connect2nearestAP.
The code looks awkward in many places - one reason ist that I started programming in C only a few month ago The other is, that there are many flaws in the ESP WiFi realization, especially in the ESP-CAM-Module. So, when I call routines again and agian, make delays, ... than this is the distillation of things I found in different discussions about the unreliable ESP32 WiFi ... with all these things it works now mostly reliable on three ESP32-CAM. And yes, my three ESP32-CAM modules do not behave in the same way. One connects to WiFi only every second reboot, one has a significantly lower signal strength than the other two. But if you google around, it seems to be normal ...
Code: Select all
#define MaxSecWiFi 30 // max time in s for WiFi setup, function will return WiFiErrorCode if WiFi was not successful.
#define WiFiErrorCode 1000 // see above
#define SaveDisconnectTime 1000 // Time im ms for save disconnection, needed to avoid that WiFi works only evey secon boot: https://github.com/espressif/arduino-esp32/issues/2501
#define WiFiTime 10 // Max time in s for successful WiFi connection.
#define WiFiOK 0 // WiFi connected
#define WiFiTimedOut 1 // WiFi connection timed out
#define WiFiNoSSID 2 // The SSID was not found during network scan
#define WiFiRSSI -75 // Min. required signal strength for a good WiFi cennection. If lower, new scan is initiated in checkWiFi()
int connect2nearestAP()
{
// this routine disconnects from WiFi, scans the network for the strongest AP at the defined SSID and tries to connect. returns WiFiOK, WiFiTimedOut, or WiFiNoSSID
int n;
int i = 0;
// the following awkward code seems to work to avoid the following bug in ESP32 WiFi connection: https://github.com/espressif/arduino-esp32/issues/2501
WiFi.disconnect(true); // delete old config
WiFi.persistent(false); //Avoid to store Wifi configuration in Flash
WiFi.mode(WIFI_OFF);
WiFi.mode(WIFI_STA);
WiFi.disconnect(true); // delete old config
WiFi.setHostname(HostName);
WiFi.begin();
delay(SaveDisconnectTime); // 500ms seems to work in most cases, may depend on AP
WiFi.disconnect(true); // delete old config
Serial.println("scan start");
n = WiFi.scanNetworks(); // WiFi.scanNetworks will return the number of networks found
Serial.println("scan done");
if (n == 0) {
Serial.println("no networks found");
} else {
Serial.print(n);
Serial.println(" networks found");
for (int i = 0; i < n; ++i) {
// Print SSID and RSSI for each network found
Serial.print(i + 1);
Serial.print(": ");
Serial.print("BSSID: ");
Serial.print(WiFi.BSSIDstr(i));
Serial.print(" ");
Serial.print(WiFi.RSSI(i));
Serial.print("dBm, ");
Serial.print(constrain(2 * (WiFi.RSSI(i) + 100), 0, 100));
Serial.print("% ");
Serial.print((WiFi.encryptionType(i) == WIFI_AUTH_OPEN) ? "open " : "encrypted ");
Serial.println(WiFi.SSID(i));
delay(10);
}
}
Serial.println();
// while ( !strcmp(ssid, &WiFi.SSID(i)) && (i < n)) {
while ( String(ssid) != String(WiFi.SSID(i)) && (i < n)) {
i++;
}
if (i == n) {
Serial.print("No network with SSID ");
Serial.println(ssid);
Serial.print(" found!");
return WiFiNoSSID;
}
Serial.print("SSID match found at: ");
Serial.println(i + 1);
WiFi.setHostname(HostName);
WiFi.begin(ssid, password, 0, WiFi.BSSID(i));
i = 0;
Serial.print("Connecting ");
while ((WiFi.status() != WL_CONNECTED) && (i < WiFiTime * 10)) {
delay(100);
Serial.print(".");
i++;
}
Serial.println();
if (WiFi.status() != WL_CONNECTED) {
Serial.print("Connection to ");
Serial.print(ssid);
Serial.println(" timed out! ");
return WiFiTimedOut;
}
Serial.print("Connected to BSSID: ");
Serial.print(WiFi.BSSIDstr());
Serial.print(" ");
Serial.print(WiFi.RSSI());
Serial.print("dBm, ");
Serial.print(constrain(2 * (WiFi.RSSI() + 100), 0, 100));
Serial.print("% ");
Serial.print(WiFi.SSID());
Serial.print(" IP: ");
Serial.println(WiFi.localIP());
return (WiFiOK);
}
void checkWiFi() { // Check the signal strength of the connection - if too low, reconnect to the strongest AP; good if the ESP is moving around and reconnection to the nearest AP makes sense
int i = 1;
if ((WiFi.status() == WL_CONNECTED) && (WiFi.RSSI() > WiFiRSSI) && (WiFi.RSSI() < -25)) { // good connection
Serial.print("Connection good: ");
Serial.print(WiFi.RSSI());
Serial.print("dBm, ");
Serial.print(constrain(2 * (WiFi.RSSI() + 100), 0, 100));
Serial.print("% ");
Serial.println(" ... keep geoing");
return;
}
while (connect2nearestAP() != WiFiOK) {
Serial.print("connect2nearestAP was called #");
Serial.println(i);
delay(1000);
i++;
if (i > 10) {
Serial.println("Rebooting cause WiFi setup failes");
ESP.restart();
}
}
}
