Lab goals:

• Learn how to set up two ESP32 wifi configurations to send UDP messages between your device and your laptop with Python.

Access Point (AP) enables your ESP32 to act as a web server that other devices can connect to

Station (STA) mode allows your ESP32 to connect to an existing network, such as Barnard Guest.

Access Point

Part 1: Programing your ESP32 to set up a Web Server

1. Read through the following Arduino code. In this example, the ESP32 will read the capacitive touch sensor value on Pin 2 and transmits a message containing its value via UDP.

#include <WebServer.h>
#include <WiFi.h>
#include <WiFiUdp.h>

// the IP of the machine to which you send msgs - this should be the correct IP in most cases (see note in python code)
#define CONSOLE_IP "192.168.1.2"
#define CONSOLE_PORT 4210

const char* ssid = "ESP32"; // TODO - replace with a unique name
const char* password = "12345678"; // you can replace with your own password

WiFiUDP Udp;

IPAddress local_ip(192, 168, 1, 1);
IPAddress gateway(192, 168, 1, 1);
IPAddress subnet(255, 255, 255, 0);
WebServer server(80);

void setup()
{
  Serial.begin(115200);
  
  WiFi.softAP(ssid, password); // setup the wifi server with the ssid & password from above
  WiFi.softAPConfig(local_ip, gateway, subnet);
  server.begin(); 
}

void loop()
{
  Udp.beginPacket(CONSOLE_IP, CONSOLE_PORT);
  // Get the value of the Touch2 sensor on the ESP32 (GPIO2, marked as Pin 2 on the board)
  // The value will typically be close to 0 when touched, and higher (~100s) when not touched
  // The value is dependent on some environmental conditions like humidity and temperature
  uint16_t touch2value = touchRead(T2);

  Serial.println(touch2value);
  
  Udp.printf(String(touch2value).c_str()); // adds Touch2 sensor value to packet payload
  Udp.endPacket();
  delay(1000);
}

1. First, update the name of the SSID for the Wifi network to something unique (so you can easily find it on your laptop) - it can, for example, be const char* ssid = "ESP32-<YourFirstName>"
2. Upload the code to your ESP32
3. Open up the Serial Monitor in Arduino to confirm that the Touch2 sensor value is being read properly. You should expect low values (around 0) when Pin 2 is touched, and higher values (around ~100s) when it is untouched.

Part 2: Reading values from ESP32 on your Laptop

You will be reading the UDP messages using a Python script.

1. First, make sure you have python installed on your computer. If you type python in your terminal and it returns a response, you should be good to go.
2. Install the socket.py library with python -m pip install socket.py
3. Download the following script and save it as reader.py

# read UPD message from the ESP32
# this code should be run on a laptop that is connected to the wifi network created by the ESP32
# note that since you are connecting your laptop to the ESP32's wifi network, you will not be able to access the internet - you will only be able to communicate with the ESP32
# for a version of this communication code that allows your laptop to still connect to the internet, see <https://gist.github.com/santolucito/4016405f54850f7a216e9e453fe81803>

import socket
# use ifconfig -a to find this IP. If your pi is the first and only device connected to the ESP32, 
# this should be the correct IP by default 
LOCAL_UDP_IP = "192.168.1.2"
SHARED_UDP_PORT = 4210
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)  # Internet  # UDP
sock.bind((LOCAL_UDP_IP, SHARED_UDP_PORT))
def loop():
    while True:
        data, addr = sock.recvfrom(2048)
        print(data.decode())
if __name__ == "__main__":
    loop()

1. Now connect your laptop to the Wifi network you established in part 1 (whatever you decided to name the SSID of your network)
2. Run the script python reader.py