Use of D8, D9, D10, D11


On your WIZ550WEB base board, you have I/O pins D8 - D11 routed to jumpers that can be used to select either a switch or an isolated input. In either case, these signals are pulled low.

I’ve learned the hard way that these signals do serve a function other than just inputs or outputs, but I can’t find those functions documented anywhere. D8 seems to have something to do with the way the module boots on power up. What happens if D8 is pulled up instead of down? What about the others?

Come on, guys. Please document these important functions so people don’t think they got a dead module just because an undocumented bit isn’t wired the way you want… :angry:



Answers to this question are critical to our program. I’ve got a rev A board where the module doesn’t boot and enable the web page like we expect, and I’m running out of time to get rev B changes in.

We are committed to buying several hundred more of these modules if we can get answers soon.



Hi, Grey.
We apologize that the development guides are insufficient.
Setting the D8 pin (GPIO_Pin_12, GPIOC) to High state and reboot the WIZ550web, the device go into Boot mode. This function for recovery when a problem occurred. (malfunction of the application firmware)

There are two methods for solving the problem.

  1. Utilize D8 pin as a boot mode switching pin only and the other input pin in the board applying to your applications.
  2. Modify the boot firmware (WIZ550web_Boot) . Change the BOOT PIN to another pin. (BOOT_PIN / BOOT_GPIO_PORT)

The WIZ550web Rev1.1 (will be released) will be available to change to the BOOT mode by use a separate switch.


Thanks, Eric.

Just to be clear, do I have to dedicate one of the 16 GPIO’s to be a boot pin (D8 being the one used with the current firmware), or can I use that boot pin for other things once the module has booted? If I can use it for an input, how long should I wait before my base board logic drives it high?



Your answer wasn’t 100% clear, so I asked for some clarification back on Feb 1.

Once again, I really need to understand how (or if) I can use D8 once the module has booted. If I need to dedicate it to the boot function alone, I can deal with that with an artwork change on the base board, but would like to know for sure. I had really hoped that a module advertised as 16-bit I/O really would be…



I would have thought this was a pretty easy question to answer. :confused:

Can I or can I not use all 16 bits? If so, under what conditions?




Hi Gray.
I’m sorry for late reply because we are in lunar new year’s holidays.

The total actual pins are 15-bit can be possible to use.
D8 pin is recommended that you do not use because the device enters to the Boot mode when D8 pin is high state and device rebooted.