WDT keeps resetting

Projects Programming
1

I've just started messing around with the WDT - I've incorporated into into one of my projects that sends data to pachube using a ethernet module. I'm using the Ethercard libraries.

Before I inserted the WDT code it all worked great - now the code keeps resetting every few seconds. If I comment out these lines then it works:

  if (!ether.dnsLookup(website))
   Serial.println(F("DNS failed"));

Here's my full code:

#include <avr/wdt.h>
#include <EtherCard.h>
#include <Wire.h>



char website[] PROGMEM = "api.pachube.com";

// ethernet interface mac address, must be unique on the LAN
byte mymac[] = { 
  0x70,0x60,0x60,0x20,0x30,0x30 };

static uint8_t myip[4] = { 
  10,1,1,20 };          //IP
static uint8_t gwip[4] = { 
  10,1,1,1 };           //Gateway IP
static uint8_t dnsip[4] = { 
  10,1,1,1 };          //DNS IP
byte Ethernet::buffer[700];
uint32_t timer;
Stash stash;


void setup () {

  wdt_enable(WDTO_2S);
  
  Serial.begin(9600);
  Serial.println(F("Setup Network"));


  if (ether.begin(sizeof Ethernet::buffer, mymac) == 0) 
    Serial.println(F("Failed to access Ethernet controller"));

  ether.staticSetup(myip, gwip, dnsip);

  ether.printIp("IP:  ", ether.myip);
  ether.printIp("GW:  ", ether.gwip);  
  ether.printIp("DNS: ", ether.dnsip);  

  if (!ether.dnsLookup(website))
   Serial.println(F("DNS failed"));


}

void loop () {

  wdt_reset();

}

Any idea where I'm going wrong?

2

You're telling the WDT to reset the processor if you don't call wdt_reset() at least every 2 seconds, then you call dnsLookup() which may take more than two seconds. Of course your system will reset!

Move the wdt_enable() to AFTER the dnsLookup() or set your wdt interval long enough that dnsLookup() will return in time.

3

Looks like the DNS lookup (plus the other things you are doing in setup()) are taking more than 2 seconds. This is entirely possible when the Ethernet connection is down.

4

Doh - as easy as that! I increased it to 8s - problem sorted!

Thanks.