UDP/IP FreeRTOS_sendto sends Packets 5 times

hisdudeness23 wrote on Monday, March 25, 2013:

I use a LPC1769 MCU with the FreeRTOS UDP/IP stack. I think I have ported the drivers correctly. I use the Standard Implementations (not the Zero Copy types).
Everytime I use the FreeRTOS_sendto() function, the packets are sent 5 times.
When I do a ping from a Linux machine, I get one normal answer-packet and 4 additional (DUP!)-Packets.

I have used the same code on the raspberry pi with the standard Linux-Berkeley-Sockets implementation and it works perfectly.

I will do some digging tonight, to localize the problem. But maybe somebody has experienced the same or a similar problem?

Thanks in advance for an answer!

The Dude.

rtel wrote on Monday, March 25, 2013:

I would concentrate your initial investigation in the driver layer - for example, is there a DMA which is sending the same packet multiple times because there is an error in the descriptor configuration (maybe the last packet is not marked as such in the descriptor)? 

I would suggest counting how many times the xNetworkInterfaceOutput() function gets called compared to how many packets you see on the wire.  That will allow us to narrow down where to look.


hisdudeness23 wrote on Monday, March 25, 2013:

Thank you very much Mr. Barry,

I will do that right now and I will post the result.

hisdudeness23 wrote on Monday, March 25, 2013:

Dear Mr. Barry,

the Number of xNetworkInterfaceOutput() function-calls matches the number of my FreeRTOS_sendto calls and the ratio of the number of packets on the wire and the sendto calls is 5:1, so I think you were right, Sir. The problem should be within the driver layer.

Thank you very much for your help!

hisdudeness23 wrote on Monday, March 25, 2013:

Problem solved!

The SendData() function had no break condition in the for-loop in a successful case. netifMAX_TX_ATTEMPTS was set to 5, so the packet was sent 5 times.

Thanks again Mr. Barry!
And sorry for interrupting your talk to the guy from i-sysem on the Embedded World. I was that dude, who asked all the questions about the UDP-IP Stack. I hope I didn’t have messed it up for you.

Best Regards,
The Dude.