How to Use WIZ811MJ: Examples, Pinouts, and Specs

The WIZ811MJ is a compact Ethernet module manufactured by WIZnet. It is designed to simplify the process of connecting microcontrollers and embedded systems to Ethernet networks. The module features a built-in hardware TCP/IP stack, which offloads the network protocol processing from the host microcontroller, enabling efficient and reliable communication.

• Internet of Things (IoT) devices
• Home automation systems
• Industrial control systems
• Network-enabled embedded systems
• Remote monitoring and data logging

The WIZ811MJ is based on the W5100 Ethernet controller and includes an RJ45 Ethernet jack with integrated magnetics. Below are the key technical details:

The WIZ811MJ module has a 2x6 pin header for interfacing with a host microcontroller. The pin configuration is as follows:

1. Power Supply: Connect the VCC pin to a 3.3V or 5V power source and the GND pin to ground.
2. SPI Interface: Connect the SCS, MOSI, MISO, and SCLK pins to the corresponding SPI pins on your microcontroller.
3. Interrupt and Reset: Optionally, connect the INT pin to a GPIO pin on your microcontroller to handle interrupts. Use the RESET pin to reset the module if needed.
4. Ethernet Connection: Plug an Ethernet cable into the RJ45 jack to connect the module to a network.

• Ensure the SPI clock speed does not exceed 25 MHz for reliable communication.
• Use decoupling capacitors near the power pins to reduce noise and improve stability.
• The module requires proper initialization of the W5100 chip before communication. Refer to the W5100 datasheet for detailed initialization steps.
• Use a level shifter if your microcontroller operates at 5V logic levels, as the WIZ811MJ operates at 3.3V logic.

Below is an example of how to use the WIZ811MJ with an Arduino UNO to establish a basic Ethernet connection:

#include <SPI.h>
#include <Ethernet.h>

// MAC address for the Ethernet module
byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };

// IP address for the device
IPAddress ip(192, 168, 1, 177);

// Initialize the Ethernet server on port 80
EthernetServer server(80);

void setup() {
  // Start the serial communication for debugging
  Serial.begin(9600);

  // Initialize the Ethernet module with the MAC and IP address
  if (Ethernet.begin(mac) == 0) {
    Serial.println("Failed to configure Ethernet using DHCP");
    // Manually configure the IP address if DHCP fails
    Ethernet.begin(mac, ip);
  }

  // Start the server
  server.begin();
  Serial.print("Server is at ");
  Serial.println(Ethernet.localIP());
}

void loop() {
  // Listen for incoming clients
  EthernetClient client = server.available();
  if (client) {
    Serial.println("New client connected");
    // Wait until the client sends data
    while (client.connected()) {
      if (client.available()) {
        char c = client.read();
        Serial.write(c); // Echo the received data to the serial monitor

        // Respond to the client
        server.write("HTTP/1.1 200 OK\r\n");
        server.write("Content-Type: text/html\r\n\r\n");
        server.write("<h1>Hello from WIZ811MJ!</h1>");
        break;
      }
    }
    // Close the connection
    client.stop();
    Serial.println("Client disconnected");
  }
}

• Replace the mac and ip variables with values appropriate for your network.
• Ensure the Ethernet library is installed in your Arduino IDE.

1. Module Not Responding

   • Ensure the power supply is stable and within the specified range.
   • Verify the SPI connections and ensure the correct pins are used.
   • Check if the RESET pin is properly connected or pulled high.

2. Unable to Obtain IP Address via DHCP

   • Verify that the Ethernet cable is securely connected to the module and the network.
   • Check if the DHCP server is active on your network.
   • Use a static IP address if DHCP fails.

3. Intermittent Connection Drops

   • Ensure the SPI clock speed is within the specified limit (25 MHz).
   • Check for noise or interference in the power supply.

4. No Response from the Server

   • Verify that the server is properly initialized and listening on the correct port.
   • Check the client code for errors in the request format.

Q: Can the WIZ811MJ be used with 5V microcontrollers?
A: Yes, but you may need a level shifter for the SPI signals, as the module operates at 3.3V logic levels.

Q: Does the module support IPv6?
A: No, the WIZ811MJ only supports IPv4.

Q: Can I use the module without an Ethernet library?
A: While possible, it is not recommended. Using a library simplifies communication and reduces development time.

Q: What is the maximum cable length supported?
A: The module follows the Ethernet standard, which supports cable lengths up to 100 meters for Cat5e or better cables.