WIZnet Developer Forum

Activity LEDs -- Wiz550io through ioShield-A

we tested a batch of Wiz550io modules with an ioShield-A and an Arduino DUE.

Test circuit:
Wiz550io plugged into ioShield-A plugged in turn into Arduino DUE.
Test procedure:

  1. plug the usb cable to supply the Arduino
  2. plug Ethernet cable form router
  3. look at activity LEDs on Ethernet receptacle.

Test results:
Some Wiz550io modules have their Activity LEDs working/blinking.
Some other modules don’t blink at all.

Why such a different behavior?
In case of no Activity LEDs does it mean that the RJ transformer is broken?
Thanks for support.


I have question to you.

What is some other modules to not blink?

I think, It is not broken RJ Transformer. because, Arduino DUE is well run.

So, we necessary checking other board.

Thank you

we tested a series (more units) of Wiz550io modules. We plugged in a Wiz550io module then tested, then unplugged it and plugged another Wiz550io. The only thing that changes is the Wiz550io module. Arduino and ioshield don’t change. See attached picture.

With some Wiz550io modules the LEDs blink. With some other Wiz550io modules no blink activity.


Ok. We will try testing that. but, it is take to time. because we no have arduino due board.

So, We will buy. Is it original arduino due? please tell me due board producer, arduino.cc? arduino.org?

We need detail board information.

And, I’m again checked your request.

Your test condition is 1 arduino due and some wiz550io test. right??

Thank you


it’s an original “Arduino DUE R3-E” from arduino.org as it’s printed at the bottom of PCB.
We tested 1 Arduino and a series of Wiz550io.
Thank you for support.


Ok Thanks.

I have 1 question.

Is there just no blink activity led??
How about link led?

Thank you

I have 1 more question.

When you bought wiz550io module??

And, which hardware version? 1.0 ? 1.1? 1.2??

If you bought 1.2 version, change 0R R16, R17, R18, R19 resistors.

Thank you

there is no activity led and no link led. LEDs are never on.
Wiz550io module version is 1.2. (0ne.Two).
thank you.


I tested. test boards is Arduino DUE R3(arduino.cc) board and 20ea wiz550io module.

It was all pass. (all normal operate to linked, activity led.)

I think, It is other problem.

where did you bought wiz550io and ioShiled-A.

What is ioShiled-A H/W version?? I tested io-Shield-A 1.1 version.

And, refer to below link to check wiz550io pin description.

there, checking J2-2 RDY pin.

below description is WIZ550io READY(RDY)pin.

This pin is asserted to low after power on.
When RSTn is activated, WIZ550io does auto configuration with embedded MAC and default IP address.
After configuration gets completed, WIZ550io raises this pin to HIGH in order to inform about the completion of WIZ550io’s configuration.
Host processor can only control WIZ55oio when RDY pin is HIGH.


ioshield-A is Ver1.1.
Could it be a NIC problem?
Could it be a ground problem? What do you think?
We’ll investigate anyway.
Thank you.


I don’t know this problem.

It is hardware problem…

So first, you using oscilloscope and checking power, gnd start.

and need test to other arduino due board.

Thank you

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