LPC1788 Ethernet corupted or missing tx packets

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by X-log on Fri Nov 29 10:54:25 MST 2013
HW: Embedded Artist LPC1788 dev board @ 120 MHz (LAN8720 over RMII)

SW: freeRTOS + lwip + zero-copy driver
Emac DMA descriptors are in peripheral RAM (0x20000000). Lwip memory pools and freertos heap are in external RAM.

Task: transmitting data over TCP at ~4mbps.

My problem is that some packets have a corrupt single lower nibble. Sometimes this also happens then packet is retransmitted, but usually fast retransmit succeeds (data is not modified/copied between retransmits,  checksum is for correct data. Maybe emac DMA reads incorrectly from external ram?)
Also, some tx packets are missing entirely.

I’m also attaching test software project.

Any help would be appreciated.

Original Attachment has been moved to: lpc1788EthTest.rar