bug in PING sample?

Arera · Joined: 23 Sep 2007 Posts: 386 Location: Wuppertal, Germany

Hi!

I'm using a W5200 in a WIZ820IO. It pings a couple of IPs (and does a lot more).
I encoutered some problems, the ram appeared corrupted after the ping.
I found out, that the ping-answer from the pinged IP is 15 bytes long.
The ping sample expects only 12 bytes to receive: dim Rec(12) As Byte.
So if I read 15 bytes to clear the buffer, 3 bytes are written anywhere into the RAM.
I do not know much about the ping protocol, maybe some day I will receive 20 Bytes?

Here is my solution:
As I do not care about the content of the ping answer (the sample does not too), I read the W5200 buffer only into ONE dummy-byte:

dim rec as byte
Res = Tcpread(idx , Rec , Result) 'get data with TCPREAD !!!

Am I right so far?
If so, maybe the sample should be changed.
If you use ping according to the sample, you should check this issue, because sometimes you do not recognize a corrupted RAM, until some fine day strange things happen.

albertsm · Joined: 09 Apr 2004 Posts: 5921 Location: Holland

maybe the w5200 puts the header into the data as well. in that case you would need 4 more bytes.
you should clear the buffer by reading 1 byte in a loop till there is no more data.

Arera · Joined: 23 Sep 2007 Posts: 386 Location: Wuppertal, Germany

11+4=15; that makes sense.
I will clear the buffer anyway, thanks a lot!