Having trouble Detecting ethernet packets using ethereal

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Hello Everyone again,

       This topic is troubling me for couple of weeks now. I want to
get over this as quickly as possible. I am trying to transmit data from
the virtex 4 LX fpga board to the PC using ethernet PHY  and i am
unable to detect any data on the PC.
       I have written a small state machine  using vhdl which actually
transmits the ethernet packet( dest MAC, Source MAC, length/type, data,
fcs(Crc)] . I am sure that FCS is correct as i tested my code for
sample ethernet packets and i got it right.

       There is a sample bit file given with the evaluation board to me
for testing the ethernet PHY.So when i download this bit file and in
the cmd , when i say ping fpga(mac address) and i start the ethereal
capture. I am able to see the data transfer to and from between fpga
and mac.
But if i dont ping it and just start capturing by clicking the capture,
i am not able to detect anything except the ARP which is data
transferred from PCs ip address to broadcast.

 In my project i dont ping in the cmd because i didnt include any ip
address in my  vhdl code. So basically i am not able to detect anything
in the ethereal except the ARP which is being transferred from PC to
broadcast. The format of the ethernet frame i am using is
Destination MAC ad, Source MAC, length/type, data, FCS(CRC) and i am
not using any ip address or udp header in my ethernet frame in the vhdl
code.

Probably the data is getting transferred on to the PC, but not able to
capture it since, i am not  pinging it.  So how do we see what data is
coming out from the PHY.

 Please advice ?

Thanks
Ashwin


Re: Having trouble Detecting ethernet packets using ethereal
Ethereal has no problems showing non-IP packets when it catches them.

Are you sending the correct preamble and SFD ? Do you see the link
blink on the PC whenever you send something ? Manually copy a static IP
packet bit by bit in your VHDL code, and send that as a test packet.
Compare your version with the sample bit file by looking at PHY signals
with a scope.


Re: Having trouble Detecting ethernet packets using ethereal
Hi Arlet
  The format i used for the ethernet frame is this: WIth the least
significand bit transferred first. I have a 4 bit interface from fpga
to PHY so i will transfer least significand nibble of each byte every
clock cycle.

7 bytes of x"55";
1 byte of x"d5";
6 bytes of dest MAC address
6 bytes of source MAC address
DATA -- 40 bytes
4 bytes of FCS

What do you mean by static IP packet. Does it include preamble and CRC
too?
The PHY converts the data into MLT-3 signal which is like a sinusoid.
Its hard to decode manually what data is being sent out.

Ashwin



Arlet wrote:
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Re: Having trouble Detecting ethernet packets using ethereal
With the static IP packet, I mean that you try to send out exactly the
same IP packet that your sample uses. Instead of implementing an entire
IP stack, you could use Ethereal to capture a good packet, look at the
hex dump, and copy it exactly in your VHDL code. Then repeatedly send
out that packet.

If you don't see your packet on Ethereal, but you see the sample, there
must be a difference. Put your scope probes between the PHY and the
FPGA to watch the digital signals. Compare between the two. Check the
preamble, bit order, timing, CRC.

Also, don't forget to pad your data if it's too short.


Re: Having trouble Detecting ethernet packets using ethereal
you may want to send a length field before the data field too.

Simon

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Re: Having trouble Detecting ethernet packets using ethereal

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With a fast digital oscilloscope ?

Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net

Re: Having trouble Detecting ethernet packets using ethereal
Or with a not so fast oscilloscope if you force 10Mb/s from the PC end link.
Aurash

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--
 __
/ /\/\ Aurelian Lazarut
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Re: Having trouble Detecting ethernet packets using ethereal
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or an optiview:
http://www.flukenetworks.com/us/LAN/Handheld+Testers/OptiView/Features/Capture+Filter+Decode.htm

     -- Mike Treseler

Re: Having trouble Detecting ethernet packets using ethereal
Hi Ashwin,

What about the 8b/10b encoding, are you encapsulating your ethernet packets
with the SOP, EOP and Carrier Extend as specified in the ieee 802.3 spec...

It's been a while but I seem to remember that in my case (my own tri-rate
mac+2vp rocketIO+external sgmii SFP) I had to encapsulate the data you
decribed as:

SOP

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EOP + CS

Also make sure you send IDLEs when you don't transmit your packet...

Regards,

--
Ignacio U. Hernandez
" I'm not normally a praying man, but if you're up there, please save me,
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