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Akhil1
Associate
Dec 3, 2019 4:07 PM UTC
Solved

STM32H7 LwIP sending raw Ethernet frames with no recognizable protocol

I am trying to setup DHCP over Ethernet using LwIP, with an ultimate goal of using TCP/UDP for communication. I have configured everything through Cube and set up the MPU according to the FAQ guidelines for Ethernet on STM32H7 and am finally receiving/sending packets.

Unfortunately the packets I receive are just raw Ethernet frames w/ no recognizable protocol. I searched around and only found one other post about this and the fix for them was to call LwIP_Process() in the main loop which I am already doing.

Here is what wire-shark is capturing on the interface the stm32 is connected to:0690X00000AtFrjQAF.png

Here is my MPU Configuration:

0690X00000AtFsrQAF.png

I have also attached my IOC file, any help will be greatly appreciated.

Edit: Providing more context:

Buffer definition:

ETH_DMADescTypeDef DMARxDscrTab[ETH_RX_DESC_CNT]
 __attribute__((section(".RxDecripSection"))); /* Ethernet Rx DMA Descriptors */
ETH_DMADescTypeDef DMATxDscrTab[ETH_TX_DESC_CNT]
 __attribute__((section(".TxDecripSection"))); /* Ethernet Tx DMA Descriptors */
uint8_t Rx_Buff[ETH_RX_DESC_CNT][ETH_RX_BUFFER_SIZE]
 __attribute__((section(".RxArraySection"))); /* Ethernet Receive Buffers */

Linker script:

/* Entry Point */
ENTRY(Reset_Handler)
 
/* Highest address of the user mode stack */
_estack = 0x24080000; /* end of RAM */
/* Generate a link error if heap and stack don't fit into RAM */
_Min_Heap_Size = 0x400; /* required amount of heap */
_Min_Stack_Size = 0x800; /* required amount of stack */
 
/* Specify the memory areas */
MEMORY
{
DTCMRAM (xrw) : ORIGIN = 0x20000000, LENGTH = 128K
RAM_D1 (xrw) : ORIGIN = 0x24000000, LENGTH = 512K
RAM_D2 (xrw) : ORIGIN = 0x30000000, LENGTH = 288K
RAM_D3 (xrw) : ORIGIN = 0x38000000, LENGTH = 64K
ITCMRAM (xrw) : ORIGIN = 0x00000000, LENGTH = 64K
FLASH (rx) : ORIGIN = 0x8000000, LENGTH = 2048K
}
 
/* Define output sections */
SECTIONS
{
 /* The startup code goes first into FLASH */
 .isr_vector :
 {
 . = ALIGN(4);
 KEEP(*(.isr_vector)) /* Startup code */
 . = ALIGN(4);
 } >FLASH
 
 /* The program code and other data goes into FLASH */
 .text :
 {
 . = ALIGN(4);
 *(.text) /* .text sections (code) */
 *(.text*) /* .text* sections (code) */
 *(.glue_7) /* glue arm to thumb code */
 *(.glue_7t) /* glue thumb to arm code */
 *(.eh_frame)
 
 KEEP (*(.init))
 KEEP (*(.fini))
 
 . = ALIGN(4);
 _etext = .; /* define a global symbols at end of code */
 } >FLASH
 
 /* Constant data goes into FLASH */
 .rodata :
 {
 . = ALIGN(4);
 *(.rodata) /* .rodata sections (constants, strings, etc.) */
 *(.rodata*) /* .rodata* sections (constants, strings, etc.) */
 . = ALIGN(4);
 } >FLASH
 
 .ARM.extab : { *(.ARM.extab* .gnu.linkonce.armextab.*) } >FLASH
 .ARM : {
 __exidx_start = .;
 *(.ARM.exidx*)
 __exidx_end = .;
 } >FLASH
 
 .preinit_array :
 {
 PROVIDE_HIDDEN (__preinit_array_start = .);
 KEEP (*(.preinit_array*))
 PROVIDE_HIDDEN (__preinit_array_end = .);
 } >FLASH
 
 .init_array :
 {
 PROVIDE_HIDDEN (__init_array_start = .);
 KEEP (*(SORT(.init_array.*)))
 KEEP (*(.init_array*))
 PROVIDE_HIDDEN (__init_array_end = .);
 } >FLASH
 
 .fini_array :
 {
 PROVIDE_HIDDEN (__fini_array_start = .);
 KEEP (*(SORT(.fini_array.*)))
 KEEP (*(.fini_array*))
 PROVIDE_HIDDEN (__fini_array_end = .);
 } >FLASH
 
 /* used by the startup to initialize data */
 _sidata = LOADADDR(.data);
 
 /* Initialized data sections goes into RAM, load LMA copy after code */
 .data :
 {
 . = ALIGN(4);
 _sdata = .; /* create a global symbol at data start */
 *(.data) /* .data sections */
 *(.data*) /* .data* sections */
 
 . = ALIGN(4);
 _edata = .; /* define a global symbol at data end */
 } >RAM_D1 AT> FLASH
 
 
 /* Uninitialized data section */
 . = ALIGN(4);
 .bss :
 {
 /* This is used by the startup in order to initialize the .bss secion */
 _sbss = .; /* define a global symbol at bss start */
 __bss_start__ = _sbss;
 *(.bss)
 *(.bss*)
 *(COMMON)
 
 . = ALIGN(4);
 _ebss = .; /* define a global symbol at bss end */
 __bss_end__ = _ebss;
 } >RAM_D1
 
 /* User_heap_stack section, used to check that there is enough RAM left */
 ._user_heap_stack :
 {
 . = ALIGN(8);
 PROVIDE ( end = . );
 PROVIDE ( _end = . );
 . = . + _Min_Heap_Size;
 . = . + _Min_Stack_Size;
 . = ALIGN(8);
 } >RAM_D1
 
 .lwip_sec (NOLOAD) : {
 . = ABSOLUTE(0x30040000);
 *(.RxDecripSection)
 
 . = ABSOLUTE(0x30040060);
 *(.TxDecripSection)
 
 . = ABSOLUTE(0x30040200);
 *(.RxArraySection)
 } >RAM_D2 AT> FLASH
 
 /* Remove information from the standard libraries */
 /DISCARD/ :
 {
 libc.a ( * )
 libm.a ( * )
 libgcc.a ( * )
 }
 
 .ARM.attributes 0 : { *(.ARM.attributes) }
}

This topic has been closed for replies.
Tesla DeLorean
Tesla DeLoreanBest answer
Guru
Dec 3, 2019 6:42 PM UTC

And what address is it *actually* using for the buffers, not just the descriptors.

Perhaps make the memory area larger, and make sure you commit any data with a fencing instruction, or explicit flush. ie __DSB, and SCB_CleanDCache_by_Addr()

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7 replies

Tesla DeLorean
Tesla DeLoreanBest answer
Guru
Dec 3, 2019 6:42 PM UTC

And what address is it *actually* using for the buffers, not just the descriptors.

Perhaps make the memory area larger, and make sure you commit any data with a fencing instruction, or explicit flush. ie __DSB, and SCB_CleanDCache_by_Addr()

Tips, Buy me a coffee, or three.. PayPal Venmo (See Profile) Up vote any posts that you find helpful, it shows what's working..
Piranha
Principal III
Dec 4, 2019 12:06 PM UTC

For these needs __DMB() is enough. In contrast to __DSB(), it leaves the possibility for a CPU to execute non memory access instructions, while waiting for a memory access to complete.

Akhil1
Akhil1Author
Associate
Dec 3, 2019 8:16 PM UTC

Oh this was it, the Txbuffer in low_level_output was on the stack and was being cached. Adding SCB_CleanInvalidDCache() before calling HAL_ETH_Transmit(....) in ethernetif.c fixed the issue for me.

Just wondering if there is a better way to do this without touching generated files (unfortunately there is no /* USER CODE */ section in low_level_output)

Piranha
Principal III
Dec 4, 2019 12:08 PM UTC

As Clive (Avogadro) already wrote, for a transmit invalidation is not necessary and clean is enough.

Akhil1
Akhil1Author
Associate
Dec 3, 2019 9:12 PM UTC

NVM got it, just used the MPU to setup the stack/heap area as Write Through RW Allocate and it works

Piranha
Principal III
Dec 4, 2019 12:13 PM UTC

Be aware of the fact, that output frames can come also from lwIP memory pools and even flash memory. Therefore D-cache management with SCB_CleanDCache_by_Addr() is more universal approach and gives more performance as the memory can be cached when processing it.

Akhil1
Akhil1Author
Associate
Dec 4, 2019 8:32 PM UTC

That makes sense but unfortunately cube doesn't have /* USER CODE */ sections in that function and we are a pretty big team so it would get messy if I modified the generated code, is there a way around this?