WIZ750SR and DHCP enabled

Wiz750SR with DCHP enabled condition, the connection is breaking more offen.
So data transfer is not completed.

Without DHCP, data transfer is working fine.

Firmware version is 1.2.4
Anybody have this issue?


I’ll give it a try as your condition in our side and let you know the result.
Please wait some time~

Dear becky

There is wrong data conversion after starting data transfer randomly.
Actual data sent on RS232 side is 66 03 00 00 97 ff but on ethernet side with wireshark is 02 01 06 00 81 4a when DHCP is enabled.


Dear Becky

Any feedback for the problem mentioned?


Sorry I’m late
I tested it, but it worked.

So I want to know your network environment or other information.
I also think that if you update the firmware to version 1.2.9 it might be helpful.

Thank you for the feedback
I have updated the firmware to 1.2.9. The problem persists.

Please find wireshark capture and config snapshot.
Use dispaly filter in wireshark as “tcp.port==4321” without quotes for viewing tcp transfers.


Please note before closing tcp connection last received data is wrong.

actual data is 66 01 00 02 97 ff
wrong data is 02 01 00 02 97 ff

If i disable DHCP, there is no issue with other settings kept same.

Kindly check and give feedback.

Thank you for your time.


Dear Becky

Any feedback for the input provided?


Dear Nagarajan,
I think, if you possible, could you please test it with another serial device such as PC terminal as Becky did? Because, until now, we can’t find some relations between DHCP enabling and serial data corruption in the code. I’m sorry not to give good feedback. Thanks,

Dear Bong
I have tested more than one module. The problem repeats with all modules.
I think there is some issue when DHCP is enabled. It randomly corrupts one or two bytes of data.

We can demostrate the problem with team viewer if possible for you check.


On your side, could you please change the serial device (not Wiz750SR, your serial device generating serial data) to the PC terminal(file read or text input) and please check the result, same or different?
Because, I think, this test can remove the uncertainty of serial original data.

On our side, we set up a loopback test env with W750SR enabling the DHCP option and will see the result during the weekend. I think, we can check the corruption of serial data through this test. So, with the result, Becky will post again.


Dear Bong

Thank you for your attention. Regarding testing at my side, i would to like point out that i am using protocol as below:

[PC Software] SOT packet 6 bytes (11 01 00 00 ee ff) ----------->
<----------- [Wiz Serial Device]ACK packet 6 bytes (66 01 00 02 97 ff)
[PC Software] CMD packet 9 bytes (33 02 01 00 ca ff 14 ec ff) ---------->
<----------- [Wiz Serial Device] ACK packet 6 bytes (66 02 00 00 98 ff)
[PC Software] DATA packet 285 bytes (22 03 15 01 c5 ff …) ---------->
<----------- [Wiz Serial Device] ACK packet 6 bytes (66 03 00 00 97 ff)

Above sequence repeats until all product(1000) is updated to embedded system.
Totally 6000 packets sent and received for 1000 products.

I am facing problem in this condition. For timing and actual data kindly refer wireshark .pcap file given earlier.

Thanks for your time.


I tested it for 2day.
But we don’t see data broken.
We have difficult to debug because can’t reenact your situation.
So I want to know your serial program, data transfer period time and data.

Also, I imaged your situation as you said.

There are problem in situation 3 or situation 4.
I think the use of dhcp does not affect data communication.
So could you please check the situation 3 as bong said.

Alternatively, please check the data sent by the serial device.
I attach firmware which can check serial data from WIZ750SR to Debugging port.
This firmware recvs serial data and sends it to the debugging port before sending it to ethernet.
W7500x_S2E_App.bin (38.8 KB)

You said 1000 products are updated.
Do you have a problem with only one product?
If you possible, could you please check it.

And I wonder you DHCP server.
please say me your DHCP server information and setting such as leasetime.

Dear Becky

Please find my testing logs.

LOG.zip (3.9 KB)
Please note with DHCP Enabled condition, data broke at 79 and 48. See the last data in each is wrongly received. Failure happens randomly.
Without DHCP, all 423 product sent successfully.

Please see below image for failure condition:

Please see below image for pass condition:

For your information, we are sure that our sending data is correct(double checked using hardware monitor). It seems, data receiving problem in Wiz750 when DHCP is enabled.

With lower baud rate 9600 also, this problem happens.
When DHCP is enabled, data is breaking.

Waiting for your reply.


So we will test with baud 4800 and enable DHCP and find out exact reason of the problem
And let you know asap.
we are afraid that can’t immediately find out exact reason in the source code.

I checked your log file and according to the log file, the uart baudrate is set to 115200
If so, the baud rate of PLU manager have to set to 115200, is it right?
If you are possible,Could you please draw the connect schematic?

PLU Manager is a software running on a PC and communicates via ethernet to WIZ750SR and then to Embedded system.

Please see block diagram.

The baud rate between WIZ750SR and Embedded System is what i meant.
With lower baud rate(9600) also, we see data breaking.


If you change the option in configuration tool or using serial command,you can see the data(ethernet to serial/ serial to ethernet).

Then, you can see the sending data through Debug UART as below.

I suspect DHCP lease time as problem. So the code of DHCP client for IP renewal has been disabled it in main.c

W7500x_S2E_App.bin (38.4 KB)

I am sure that disabling through config tool or commenting DHCP_run(); is same.

My point is when DHCP is enabled condition, i see issue. So please check DHCP_run() for errors/time spent/enable or disable RS232 or it is being called too frequently. Can you insert a delay say 50 millsecond between call? and give ME .bin file.

We want work with DHCP enabled condition.


Please find log file
20200109104259.zip (7.7 KB)

The last data is wrong
[00:02:04][S2E][0006] 02 01 06 00 F9 50

It should be 66 01 00 02 97 FF

Waiting for solution.

Is there any chance of sending wrong serial data in your embedded system?
Could you please change the Inactivity time is ‘0’ in connection timer settingand Try again test ?
Let me check at the DHCP-related code one more time.