A Motor Shield Wemos ESP8266, it's good for build Wifi Robot Car controlled by Android phone.

You can find circuit diagram and source code on app ESP8266 WiFi Robot Car:

• Remote Control Mode:
• Obstacle Avoidance
• Object Follower
• Line Follower

Circuit Diagram:

Sketch Code Remote Control mode:

/******************* WiFi Robot Remote Control Mode ********************/ #include <ESP8266WiFi.h> #include <ESP8266WebServer.h> #include <ArduinoOTA.h> // connections for drive Motors int PWM_A = D1; int PWM_B = D2; int DIR_A = D3; int DIR_B = D4; const int buzPin = D5;   // set digital pin D5 as buzzer pin (use active buzzer) const int ledPin = D8;   // set digital pin D8 as LED pin (use super bright LED) const int wifiLedPin = D0; // set digital pin D0 as indication, the LED turn on if NodeMCU connected to WiFi as STA mode String command;     // String to store app command state. int SPEED = 1023;    // 330 - 1023. int speed_Coeff = 3; ESP8266WebServer server(80);   // Create a webserver object that listens for HTTP request on port 80 unsigned long previousMillis = 0; String sta_ssid = "$your_ssid_maximum_32_characters";   // set Wifi networks you want to connect to String sta_password = "$your_pswd_maximum_32_characters"; // set password for Wifi networks void setup(){ Serial.begin(115200);  // set up Serial library at 115200 bps Serial.println(); Serial.println("*WiFi Robot Remote Control Mode*"); Serial.println("--------------------------------------");  pinMode(buzPin, OUTPUT);   // sets the buzzer pin as an Output pinMode(ledPin, OUTPUT);   // sets the LED pin as an Output pinMode(wifiLedPin, OUTPUT); // sets the Wifi LED pin as an Output digitalWrite(buzPin, LOW); digitalWrite(ledPin, LOW); digitalWrite(wifiLedPin, HIGH);    // Set all the motor control pins to outputs pinMode(PWM_A, OUTPUT); pinMode(PWM_B, OUTPUT); pinMode(DIR_A, OUTPUT); pinMode(DIR_B, OUTPUT);   // Turn off motors - Initial state digitalWrite(DIR_A, LOW); digitalWrite(DIR_B, LOW); analogWrite(PWM_A, 0); analogWrite(PWM_B, 0); // set NodeMCU Wifi hostname based on chip mac address String chip_id = String(ESP.getChipId(), HEX); int i = chip_id.length()-4; chip_id = chip_id.substring(i); chip_id = "wificar-" + chip_id; String hostname(chip_id);   Serial.println(); Serial.println("Hostname: "+hostname); // first, set NodeMCU as STA mode to connect with a Wifi network WiFi.mode(WIFI_STA); WiFi.begin(sta_ssid.c_str(), sta_password.c_str()); Serial.println(""); Serial.print("Connecting to: "); Serial.println(sta_ssid); Serial.print("Password: "); Serial.println(sta_password); // try to connect with Wifi network about 10 seconds unsigned long currentMillis = millis(); previousMillis = currentMillis; while (WiFi.status() != WL_CONNECTED && currentMillis - previousMillis <= 10000) {  delay(500);  Serial.print(".");  currentMillis = millis(); } // if failed to connect with Wifi network set NodeMCU as AP mode if (WiFi.status() == WL_CONNECTED) {  Serial.println("");  Serial.println("*WiFi-STA-Mode*");  Serial.print("IP: ");  Serial.println(WiFi.localIP());  digitalWrite(wifiLedPin, LOW);  // Wifi LED on when connected to Wifi as STA mode  delay(3000); } else {  WiFi.mode(WIFI_AP);  WiFi.softAP(hostname.c_str());  IPAddress myIP = WiFi.softAPIP();  Serial.println("");  Serial.println("WiFi failed connected to " + sta_ssid);  Serial.println("");  Serial.println("*WiFi-AP-Mode*");  Serial.print("AP IP address: ");  Serial.println(myIP);  digitalWrite(wifiLedPin, HIGH);  // Wifi LED off when status as AP mode  delay(3000); }  server.on ( "/", HTTP_handleRoot );    // call the 'handleRoot' function when a client requests URI "/" server.onNotFound ( HTTP_handleRoot );  // when a client requests an unknown URI (i.e. something other than "/"), call function "handleNotFound" server.begin();              // actually start the server   ArduinoOTA.begin();            // enable to receive update/uploade firmware via Wifi OTA } void loop() {  ArduinoOTA.handle();     // listen for update OTA request from clients  server.handleClient();    // listen for HTTP requests from clients      command = server.arg("State");     // check HTPP request, if has arguments "State" then saved the value   if (command == "F") Forward();     // check string then call a function or set a value   else if (command == "B") Backward();   else if (command == "R") TurnRight();   else if (command == "L") TurnLeft();   else if (command == "G") ForwardLeft();   else if (command == "H") BackwardLeft();   else if (command == "I") ForwardRight();   else if (command == "J") BackwardRight();   else if (command == "S") Stop();   else if (command == "V") BeepHorn();   else if (command == "W") TurnLightOn();   else if (command == "w") TurnLightOff();   else if (command == "0") SPEED = 330;   else if (command == "1") SPEED = 400;   else if (command == "2") SPEED = 470;   else if (command == "3") SPEED = 540;   else if (command == "4") SPEED = 610;   else if (command == "5") SPEED = 680;   else if (command == "6") SPEED = 750;   else if (command == "7") SPEED = 820;   else if (command == "8") SPEED = 890;   else if (command == "9") SPEED = 960;   else if (command == "q") SPEED = 1023; } // function prototypes for HTTP handlers void HTTP_handleRoot(void){ server.send ( 200, "text/html", "" );    // Send HTTP status 200 (Ok) and send some text to the browser/client   if( server.hasArg("State") ){   Serial.println(server.arg("State")); } } void handleNotFound(){ server.send(404, "text/plain", "404: Not found"); // Send HTTP status 404 (Not Found) when there's no handler for the URI in the request } // function to move forward void Forward(){  digitalWrite(DIR_A, HIGH); digitalWrite(DIR_B, HIGH); analogWrite(PWM_A, SPEED); analogWrite(PWM_B, SPEED); } // function to move backward void Backward(){ digitalWrite(DIR_A, LOW); digitalWrite(DIR_B, LOW); analogWrite(PWM_A, SPEED); analogWrite(PWM_B, SPEED); } // function to turn right void TurnRight(){ digitalWrite(DIR_A, LOW); digitalWrite(DIR_B, HIGH); analogWrite(PWM_A, SPEED); analogWrite(PWM_B, SPEED); } // function to turn left void TurnLeft(){ digitalWrite(DIR_A, HIGH); digitalWrite(DIR_B, LOW); analogWrite(PWM_A, SPEED); analogWrite(PWM_B, SPEED); } // function to move forward left void ForwardLeft(){ digitalWrite(DIR_A, HIGH); digitalWrite(DIR_B, HIGH); analogWrite(PWM_A, SPEED); analogWrite(PWM_B, SPEED/speed_Coeff); } // function to move backward left void BackwardLeft(){ digitalWrite(DIR_A, LOW); digitalWrite(DIR_B, LOW); analogWrite(PWM_A, SPEED); analogWrite(PWM_B, SPEED/speed_Coeff); } // function to move forward right void ForwardRight(){ digitalWrite(DIR_A, HIGH); digitalWrite(DIR_B, HIGH); analogWrite(PWM_A, SPEED/speed_Coeff); analogWrite(PWM_B, SPEED); } // function to move backward left void BackwardRight(){  digitalWrite(DIR_A, LOW); digitalWrite(DIR_B, LOW); analogWrite(PWM_A, SPEED/speed_Coeff); analogWrite(PWM_B, SPEED); } // function to stop motors void Stop(){   digitalWrite(DIR_A, LOW); digitalWrite(DIR_B, LOW); analogWrite(PWM_A, 0); analogWrite(PWM_B, 0); } // function to beep a buzzer void BeepHorn(){ digitalWrite(buzPin, HIGH); delay(150); digitalWrite(buzPin, LOW); delay(80); } // function to turn on LED void TurnLightOn(){ digitalWrite(ledPin, HIGH); } // function to turn off LED void TurnLightOff(){ digitalWrite(ledPin, LOW); }