WIZ550WEB-EVB controls power supply of WIZ107SR-TTL-EVB – part #2

First we need to determine the command that will be sent to the webserver to toggle one of the outputs. We therefore make use of the wireshark program to capture the http stream that will be sent to the webserver after having clicked a button on the WIZ550WEB-EVB website.

Picture 1: Screenshot of wireshark
Picture 1: Screenshot of wireshark

After having found the right tcp stream we can figure out, that we simply have to send this POST request to our webserver (IP:


 This can be done with the use of the cURL package – this package can send HTTP POST requests from the command line and act as if it was a user clicking on a web page. The simple. but complete command to send a HTTP POST request with cURL is:

curl –silent –output out.txt –data “pin=6&val=1”

This command forces the relay on output #6 of our WIZ550WEB-EVB to close. In the same way the relay can also be forced to open again by simply changing the value of “val” to 0. If the relay is closed, the WIZ107SR-TTL will be powered on. Including these requests into a small bash script can automate the power cycling really easy – we just have to add some wait states for the right timing and everything can be read in our PuTTY log clearly. As an example a bash script could look like this:

while [ true ]; do
echo “module on”
curl –silent –output out.txt –data “pin=6&val=0”
sleep 15
echo “module off”
curl –silent –output out.txt –data “pin=6&val=1”
sleep 5

In this screenshot you can see our bash script toggling the WIZ107SR-TTL operating voltage and the PuTTY log for the serial console, as well as the 550WEB Demopage that shows us the state of the relay #6:

Picture 2: Overview

Our primary goal was to check the long-time functionality of the WIZ107SR-TTL dns functionality – we can clearly see that if the DNS does not resolve properly or cannot be reached, that there are plenty of error messages on the serial interface of the WIZ107SR-TTL-EVB:

DNS fail log
Picture 3: DNS fail log

Using the log functionality of PuTTY we can write every boot sequence of the WIZ107SR-TTL to a text file. There are plenty of tools that can easily analyse this log file for error messages. In our first testing sequence of 600 power cycles of the WIZ107SR-TTL we did not have one failure.

Please feel free to contact us  at support AT wiznet DOT eu in case you have any questions regarding this article – fk.