UDP data packet on W5500

TCP/IP Chip W5500
#1

All,

I am looking at the code for the UDP receive function, UDPRecv.
It is taking the first 6 bytes as being the destination IP address?
I thought the header was like this:
2 bytes, source port
2 bytes, destination port
2 bytes, data length
2 bytes, check sum
Then the data.

Is the W5500 changing the UDP header, or am I missing something here?

Thanks,
Jim

#2

Yes, the W5500 (and also W5200 and W5100) return a custom UDP packet info structure.

I think the W5500 manual misses this information, but the W5200 manual has it, look it up there.

UDP data is specially structured in the RX memory, like this:

PACKET-INFO
4 bytes: destination IP address
2 bytes: destination port number
2 bytes: byte size (N) of data packet
DATA-PACKET
N bytes: real data

#3

Hi,
As ventosus said, The rx buffer for UDP have no 2byte checksum because it is off-loaed by W5500.
The udp header info rx buffer is re-ordered by WIZnet.
Thank you.

#4

Hi,

W5x00 series all have the same UDP header frame.

dd.jpg780×233 46 KB

Best regards.

#5

Thanks for the reply.
I got the W5200 manual and that answered a few questions I had.
The whole section 5 of the W5200 data sheet is missing from the W5500 manual,
I hope this gets included in the W5500 datasheet for people like me that have not
used a previous wiz chip.

Thanks,
Jim

#6

Hi!

I am a bit confused about this UDP checksum.
Does W5500 generate it? If not, who does?

Below is a screenshot of a of package sent by w5500. Checksum is definitely present.
Where is it generated? Can it be configured?

image
image1056×574 24.2 KB

Thank you.

#7

Dear Luckyluka!

Unverified Checksum caused by wireshark setting.
Refer to https://www.wireshark.org/lists/wireshark-dev/201607/msg00022.html

Thank you.