W5200 - sending time


#1

Dear support,

I am quite new with W5200 and have a question about the time peformances. here is my situation:

I have interfaced a W5200 with a PIC32MX by microchip. From the system point of view, everything is fine: I can both receive and transmit data from/to the PC in UDP with a 100 MHh rate.

Nevertheless, I am quite surprised about the timing performances. Indeed, I send a small data packet (around 50 bytes) to the W5200 that puts the nINT pin low. This start an interrupt in my PIC32. In this interrupt, the PIC32 reads the 50 bytes from the W5200, process them, write the return data (~20 bytes) in the W5200 TxBuffer and write the send command in the Sn_CR. All this takes ~250 us (measured with a scope).

But, if I take a look at this exchange with WireShark, there is ~650 us between the two captured packet. So, here is my question: Where does the difference come from??? 400 us seems a lot to process the “send command”, isn’t it? Indeed, such a difference decrease A LOT the achievable throughput.

Am I doing something wrong or are these 400 us a normal value?

Best regards,

Christian


#2

Hi, crod.

Two captured packets in wireshark contain network delay.

W5200 <------delay--------> PC

So you cannot control the delay. If your network are slower(traffic increased), the delay could be increased. Or if your network are faster, the delay could be decreased.

And TCP has send/receive ACK then re-transmission. So the delay could be more increased. So you need to consider network speed.

Best regards.