Unable to configure Ethernet using Arduino Uno R3

Question

I have purchased an Arduino Uno R3 board and a LAN shield from these locations:

• Arduino UNO R3
• Arduino LAN shield

I am trying to configure Ethernet using this sketch:

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

// Enter a MAC address for your controller below.
// Newer Ethernet shields have a MAC address printed on a sticker on the shield
byte mac[] = {
  0x4,0x2,0x45,0x68,0x5E,0x96,0x56
};

// Initialize the Ethernet client library
// with the IP address and port of the server
// that you want to connect to (port 80 is default for HTTP):
EthernetClient client;

void setup() {
  // Open serial communications and wait for port to open:
  Serial.begin(9600);
  delay(5000);
  // this check is only needed on the Leonardo:
  while (!Serial) {
    ; // wait for serial port to connect. Needed for Leonardo only
  }
  // start the Ethernet connection:
  Serial.println("trying to configure ethernet...");
  while(Ethernet.begin(mac) == 0) {
    Serial.println("Failed to configure Ethernet using DHCP, retrying after 5 sec");
    // no point in carrying on, so do nothing forevermore:
    delay(5000);
    Serial.println("trying to configure ethernet...");
  }
  // print your local IP address:
  Serial.print("My IP address: ");
  for (byte thisByte = 0; thisByte < 4; thisByte++) {
    // print the value of each byte of the IP address:
    Serial.print(Ethernet.localIP()[thisByte], DEC);
    Serial.print(".");
  }
  Serial.println();
}

void loop() {
}

It generates this output in the Serial Monitor:

trying to configure ethernet...
Failed to configure Ethernet using DHCP, retrying after 5 sec
trying to configure ethernet...
Failed to configure Ethernet using DHCP, retrying after 5 sec
trying to configure ethernet...
Failed to configure Ethernet using DHCP, retrying after 5 sec
trying to configure ethernet...
Failed to configure Ethernet using DHCP, retrying after 5 sec
trying to configure ethernet...
Failed to configure Ethernet using DHCP, retrying after 5 sec
trying to configure ethernet...
Failed to configure Ethernet using DHCP, retrying after 5 sec
trying to configure ethernet...
Failed to configure Ethernet using DHCP, retrying after 5 sec
trying to configure ethernet...

I have captured the LED indicators on video on YouTube, it shows Tx and Rx LEDs glowing occasionally, see Arduino not detecting the ethernet connection.

It looks like the Arduino is not able to connect to the Ethernet... I am using the Arduino IDE 1.6.5 on Windows 7.

Is there any debug tool for Arduino that can be used to figure out this issue?

Answer 1

I use more or less the same code to do my networked widgets and it has been quite reliable in my experience. Do you know if you have a DHCP server on the network segment that the Arduino is on? The absence of a server or a configuration that won't respond to the Arduino seem like the most likely explanation for the problem you're seeing.

The way to troubleshoot this would be to get another machine on the same network segment and watch the traffic with tcpdump or Wireshark or a similar tool. If you're running on a "third party" machine (e.g. not the DHCP server) then you'll be able to see the Arduino's side of the DHCP exchange, but I'm not sure if you'll be able to see the server (the Arduino will be broadcasting since it can't know the address of the DHCP server, but I think the server's response is unicast). If you've got a Linux box or some other machine that you can log into where you could run the DHCP server you can watch both sides of the negotiation. But even if you can't get to the server it will help to see if the Arduino is starting the DHCP negotiation.

If you need a fixed IP address on the Arduino, the way to do it is to configure the DHCP server to reserve an address for the Arduino. That way you can have a known address on the Arduino without having to hard code an IP address (which will eventually bite you).

Answer 2

I never used the DHCP feature to assign an IP address for the Ethernet shield, but somewhere in there you have to list the IP of the router that assigns the DHCP.

In everyday use of the shield, you don't want your router to assign an IP address to your device because every time it connects it might get a different IP address. That means if you want to communicate with it, you need to discover the IP address each time. And communicating with it from the WAN side through a port you open in your router would be impossible.

Try one of the fixed IP address sketches, but select a free IP address in your router's IP range that isn't, also, in the router's DHCP IP range (that way the fixed IP address won't interfere with the IP addresses given out automatically).