MCU-PLUS-SDK-AM243X: UDP packet payload not sent

Yanyves Genereux

Hello,

I am facing an issue where an answer to a broadcast list identity (EIP protocol) is working once but it is failing afterward. I am using LWIP and the SDK 8.05

For the first try it will enter the function etharp_query() which will then aggregate the whole packet in one payload and it will be sent through the tcpip_thread(). This is working fine.

Now for the second list identity the arp is not needed so we enter etharp_output_to_arp_index() with the cached entry. In this function we have the ethernet frame as two parts like this:

On wireshark we only see the part1 being sent out, but never part2. This lead to have a malformed packet like this :

Would you have any idea on what could cause this ?

Thank you!

Regards

over 2 years ago

0 Nilabh Anand over 2 years ago

TI__Guru 53100 points

Hi ,

Can you please share more info:

Are you facing this issue with sdk example or is this a modified example?

Can you share the example project it will help us debug faster?

0 Yanyves Genereux over 2 years ago in reply to Nilabh Anand

Prodigy 30 points

Hello,
Thank you for your answer, I am using my own modified code and not an example code.

I found one solution, but it it maybe not the solution to this problem.

I had this define set to 0 and setting it to 1 fixes the problem: LWIP_NETIF_TX_SINGLE_PBUF

My question now is what could cause the scatter-gather to be not supported ?

In LWIP documentation I see this :

It states that with this define enabled we will do CPU memcpy, so I would like to be sure to understand why we need this define before closing this thread.

Regards

Yanyves

0 Nilabh Anand over 2 years ago in reply to Yanyves Genereux

TI__Guru 53100 points

Hi Yanyves,

Yanyves Genereux said:
I had this define set to 0 and setting it to 1 fixes the problem: LWIP_NETIF_TX_SINGLE_PBUF

My question now is what could cause the scatter-gather to be not supported ?

ICSS EMAC driver does not use DMA, hence scatter gather is not implemented. ICSS EMAC driver is used beneath EIP PRU FW HAL. For more details on ICSS EMAC:

AM243x MCU+ SDK: ICSS-EMAC (ti.com)

0 Yanyves Genereux over 2 years ago in reply to Nilabh Anand

Prodigy 30 points

Hello,

Thank you for your answer.

The definition says "This is for compatibility with DMA-enabled MACs that do not support scatter-gather." it is not saying that system without DMA does not support scatter-gather automatically. But if you tell me that on the SDK this feature is not supported then yes I will keep that flag LWIP_NETIF_TX_SINGLE_PBUF set to 1.

Regards

0 Nilabh Anand over 2 years ago in reply to Yanyves Genereux

TI__Guru 53100 points

Hi Yanyves

It prevents pbuf chain from getting created thus disabling scatter-gather. It is also the configuration enforced by SDK default also.

0 Yanyves Genereux over 2 years ago in reply to Nilabh Anand

Prodigy 30 points

Hello,

Per default this define LWIP_NETIF_TX_SINGLE_PBUF is set to 0 in the SDK file C:\ti\mcu_plus_sdk_am243x_08_06_00_45\source\networking\lwip\lwip-config\am243x\lwipopts.h

But I take note of what you say and we will keep it defined to 1 from now on.

Thanks

Regards

0 Nilabh Anand over 2 years ago in reply to Yanyves Genereux

TI__Guru 53100 points

Hi Yanyves,

This lwipo opts is not used for ethernetip. This lwip opts is for DMA based enet driver.

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MCU-PLUS-SDK-AM243X: UDP packet payload not sent