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STM32F407VG + LwIP Rx works but TX does not

Question asked by mueller.stefan on Jan 15, 2016
Latest reply on Jan 15, 2016 by Edje

I use my own board with a STM32F407VG controller. I tried to get the LwIP 1.4.1 example running, that can be downloaded from the website. After adopting the BSP to my board I can receive packets perfectly. e.g. I send ARP requests from a PC and in debug mode I can see the correct receive data in the buffers.
But the reply to a received request does not work. In the file ethernetif.c  at line 156 it checks
/* Is this buffer available? If not, goto error */
      if((DmaTxDesc->Status & ETH_DMATxDesc_OWN) != (u32)RESET)

The result is always, that the descriptor is owned by the CPU and not by the DMA and so it goes into error state and does not continue to transmit the data.

Has anybody an idea, why the descriptor is not owned by the DMA at this point? Did I miss some configuration?

Thank you very much,