Lost bytes with Wiz 107SR

Good morning,

We have been doing development on our product using the wiz107sr. We have tried every firmware and many different baud rates and serial packing conditions and we still notice that serial data is overrunning the ethernet in some cases. resulting in data loss. We use a 160 byte packet with a crc and maybe 1% of the packets come through with data missing. The next packet will overwrite the end of the previous one and invalidate it.

Our current best setting is a timer of 50ms and size and character of 0.

Is some amount of data loss expected or are there things we can do to avoid this?

Is this module suited for reliable data transfer or should we be using a different model?

Thank you

Hi cory.
We are updated new version firmware for WIZ107/108SR. (v4.04)
It is the bug fixed version: data loss problem, DHCP lease time checker.

The new firmware has not been updated yet but it will be updated soon at our website.
I’ve attached WIZ107SR v4.04 firmware in this post for you.
Please try updated your module using this firmware.
(This firmware version is for Rev.1.3 / 1.4 only. not WIZ107SR Rev 1.1)

WIZ107SRv4_04.zip (21.6 KB)



Thank you for the response. We have been testing the 4.04 firmware and unfortunately, we still see the same data loss.

Additional testing seems to indicate that the frequency of data loss is related to the network conditions. Connections on the same network segment are the most reliable with less than 1% loss. When we connect to an Amazon EC2 instance, the loss varies from 5%-20%.

Debugging the hardware shows the data entering the serial buffer correctly, but Wireshark logs show the bytes missing when they leave the wiznet module.

Our best guess is that there is an issue with the flow control between the serial and ethernet buffers. Do we have a way to see the state of the ethernet buffer and not put data on the serial buffer until it is ready?

Note: Our normal traffic is 160 bytes every few seconds. This byte loss happens primarily when we send data at a higher rate, though the max rate we send to the serial buffer is 3,200 Bps.

Thank you for any insight you can provide.

Just checking back to see if anyone has any insight into this.

Thank you