Ethernet packet missing for Gigabit camera

[Mehrdad Salami]

Hi,

I have a board similar to Freescale EVB board for 5475. I am using Linux
LTIB from freescale. I am connecting a gigabit
camera to the Ethernet port to receive images from the camera.

The problem is when the camera sending pictures in UDP packets of 1500
bytes, The application I have for reading packets, misses many
packets.The link is 100BASE-TX.
If I increase the time between packets (Ask Camera to send packets with
long delay) then all packets will be received. However if the delay
between packets is short, the application missing packets depends on the
delay.

I tried to increase the priority of program, priority of DMA, priority
of receive channel on Ethernet but none of those changed the rate of
missing packets. Is there anyway to increase the speed of receiving
packet on Ethernet
port in application. Would it be faster if part of code transferred to
kernel to speed up operation.

Just to have idea of the data and time , the camera sending 211 packet
of 1500 bytes in 50ms and I am only reading 64 packets.  The transfer
data rate is 211*1500*8*20=50Mbit/s . Is this too close to 100Mbit/s
maximum speed of Ethernet for coldfire to handle. I think the 1500
packet size is only data and it must have more overhead inside packet.



Thanks,


Mehrdad Salami
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[Markus Franke]

Hi,

Mehrdad Salami schrieb:
> Just to have idea of the data and time , the camera sending 211 packet
> of 1500 bytes in 50ms and I am only reading 64 packets.  The transfer
> data rate is 211*1500*8*20=50Mbit/s . Is this too close to 100Mbit/s
> maximum speed of Ethernet for coldfire to handle. I think the 1500
> packet size is only data and it must have more overhead inside packet.

I am working on a similiar board featuring an MCF5484 cpu. I measured
the bandwidth of Ethernet with the netperf/netserver tool[1] and I
reached between 40 (TCP STREAM) to 50 Mbit/s (UDP STREAM). I don't know
why the bandwidth is just half of the nominal 100 Mbit/s. It might be a
performance problem of the driver.
Maybe you should use the netperf tool in a first step and measure your
ethernet bandwidth independently from your camera specific stuff.

Hope this helps,

Markus

[1] http://www.netperf.org/netperf/
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