CCS/RM57L843: RM57L + FreeRTOSUDP can't support send data length>18

H Gong

Part Number: RM57L843

Tool/software: Code Composer Studio

I have TMDXRM57LHDK. After compile UDP demo under FreeRTOS UDP/IP protocol and try, I found it can't send the frame data below 18 bytes. If the byte count reach 18 Bytes or more, no problem. After Trace by debug, I guess the problem happens on the EMAC drive(HL_emac.c). Please help.

Again, I guess the problem shall happen in function xNetworkInterfaceOutput(). If I change the tot_len and len into 60, then the data frame can be sent out.

struct pbuf_struct* pbuf = 0;

/* Get a buffer and initialize it */
xGetPbuf(&pbuf);
pbuf->next = 0; /* No linked buffer chain */
pbuf->payload = pxNetworkBuffer->pucEthernetBuffer;
pbuf->tot_len = (uint16)(pxNetworkBuffer->xDataLength & 0xFFFF);
pbuf->len = pbuf->tot_len; /* no linked buffer chain */

over 8 years ago

0 Chuck Davenport over 8 years ago

TI__Guru 59540 points

Hello,

Please see this post on LWIP+UDP implementation.

e2e.ti.com/.../482999

Specifically, the minimum packet length topic is addressed about 2/3rds through the thread.

0 H Gong over 8 years ago in reply to Chuck Davenport

Prodigy 100 points

Thanks for your quick response. Before this topic is posted I have got the root cause for it:

limited by MIN_PKT_LEN.

A work round can be added here:

if(pbuf->tot_len<MIN_PKT_LEN)

{

pbuf->tot_len=MIN_PKT_LEN);

}

pbuf->lenpbuf->tot_len;

0 Chuck Davenport over 8 years ago in reply to H Gong

TI__Guru 59540 points

Hello Gong,

So it seems the SW can be changed to allow shorter packets? This is OK for proprietary implementations but I think the standard protocol formats require a minimum of 60 bytes in a packet which means a minimum of 18 data bytes once you account for the packet header and other protocol related content.

Arm-based microcontrollers

Arm-based microcontrollers forum

CCS/RM57L843: RM57L + FreeRTOSUDP can't support send data length>18