Integrating micro‑ROS over UDP using LWIP and FreeRTOS on the STM32H723ZG Nucleo Board

[tapererwaj]

Hello everyone,

I’m currently working with the STM32H723ZG Nucleo board and am trying to interface microROS using UDP transport. I’m using the following environment:

• STM32CubeIDE: v1.16.1
• STM32Cube Firmware: H7 V1.11.2
• Toolchain: GNU Tools for STM32 (GCC 12.3.rel1)

I’ve carefully reviewed several guides covering MPU, Ethernet, LWIP, and FreeRTOS configurations. I was able to get microROS working over USART (per the Micro_ROS guide), but when I attempt the UDP transport I encounter a hard fault. I’ve tried replicating setups from the STM32H723_Nucleo_ETH and LWIP_UDP_Echo_Server examples (generated by CubeMX), but they don’t work as expected.

My project files are available here: tapererwaj/h723zg_microros_udp

Below, I have summarized my current configuration:

---

MPU Configuration

SCB_EnableICache();
SCB_EnableDCache();

/* Region 0: Ethernet DMA descriptors */
MPU_InitStruct.Enable = MPU_REGION_ENABLE;
MPU_InitStruct.Number = MPU_REGION_NUMBER0;
MPU_InitStruct.BaseAddress = 0x0;
MPU_InitStruct.Size = MPU_REGION_SIZE_4GB;
MPU_InitStruct.SubRegionDisable = 0x87;
MPU_InitStruct.TypeExtField = MPU_TEX_LEVEL0;
MPU_InitStruct.AccessPermission = MPU_REGION_NO_ACCESS;
MPU_InitStruct.DisableExec = MPU_INSTRUCTION_ACCESS_DISABLE;
MPU_InitStruct.IsShareable = MPU_ACCESS_SHAREABLE;
MPU_InitStruct.IsCacheable = MPU_ACCESS_NOT_CACHEABLE;
MPU_InitStruct.IsBufferable = MPU_ACCESS_NOT_BUFFERABLE;
HAL_MPU_ConfigRegion(&MPU_InitStruct);

/* Region 1: Ethernet/LWIP heap region */
MPU_InitStruct.Number = MPU_REGION_NUMBER1;
MPU_InitStruct.BaseAddress = 0x30000000;
MPU_InitStruct.Size = MPU_REGION_SIZE_32KB;
MPU_InitStruct.SubRegionDisable = 0x0;
MPU_InitStruct.TypeExtField = MPU_TEX_LEVEL1;
MPU_InitStruct.AccessPermission = MPU_REGION_FULL_ACCESS;
MPU_InitStruct.IsShareable = MPU_ACCESS_NOT_SHAREABLE;
HAL_MPU_ConfigRegion(&MPU_InitStruct);

/* Region 2: Additional region (512B) */
MPU_InitStruct.Number = MPU_REGION_NUMBER2;
MPU_InitStruct.Size = MPU_REGION_SIZE_512B;
MPU_InitStruct.TypeExtField = MPU_TEX_LEVEL0;
MPU_InitStruct.IsShareable = MPU_ACCESS_SHAREABLE;
MPU_InitStruct.IsBufferable = MPU_ACCESS_BUFFERABLE;
HAL_MPU_ConfigRegion(&MPU_InitStruct);

/* Enable the MPU */
HAL_MPU_Enable(MPU_PRIVILEGED_DEFAULT);

FreeRTOS Configuration

• Task definition:
  FREERTOS.Tasks01=defaultTask,24,512,StartDefaultTask,Default,NULL,Dynamic,NULL,NULL
• Stack overflow checking enabled: FREERTOS.configCHECK_FOR_STACK_OVERFLOW=1
• Minimal stack size: FREERTOS.configMINIMAL_STACK_SIZE=512
• Total heap size: FREERTOS.configTOTAL_HEAP_SIZE=30*1024
• Newlib reentrancy enabled: FREERTOS.configUSE_NEWLIB_REENTRANT=1

Ethernet (ETH) Settings

• Interface: ETH.MediaInterface=HAL_ETH_RMII_MODE
• Receive Buffer Address: ETH.RxBuffAddress=0x30000200
• Receive Buffer Length: ETH.RxBuffLen=1536
• Tx Descriptor Address: ETH.TxDescAddress=0x30000100

LWIP Configuration

• Default thread stack size: LWIP.DEFAULT_THREAD_STACKSIZE=2048
• Static IP: LWIP.IP_ADDRESS=192.168.1.10
• DHCP disabled: LWIP.LWIP_DHCP=0
• LWIP heap pointer: LWIP.LWIP_RAM_HEAP_POINTER=0x30000200
• MEM_SIZE: LWIP.MEM_SIZE=32232
• Netmask: LWIP.NETMASK_ADDRESS=255.255.255.0
• TCP/IP thread stack size: LWIP.TCPIP_THREAD_STACKSIZE=2048
• TCP MSS: LWIP.TCP_MSS=1460
• TCP SND_BUF: LWIP.TCP_SND_BUF=5840
• TCP SND_QUEUELEN: LWIP.TCP_SND_QUEUELEN=16

Linker Script Modifications

/* Modification start */
   .lwip_sec (NOLOAD) :
  {
    . = ABSOLUTE(0x30000000);
    *(.RxDecripSection) 
    
    . = ABSOLUTE(0x30000100);
    *(.TxDecripSection)
    
  } >RAM_D2
  /* Modification end */

LWIP Options (lwipopts.h)

#define WITH_RTOS 1
#undef LWIP_PROVIDE_ERRNO

#define CHECKSUM_BY_HARDWARE 1
#define ETH_RX_BUFFER_SIZE 1536
#define MEM_ALIGNMENT 4
#define MEM_SIZE 32232
#define LWIP_RAM_HEAP_POINTER 0x30000200
#define LWIP_SUPPORT_CUSTOM_PBUF 1
#define LWIP_ETHERNET 1
#define LWIP_DNS_SECURE 7
#define TCP_MSS 1460
#define TCP_SND_BUF 5840
#define TCP_SND_QUEUELEN 16
#define LWIP_NETIF_LINK_CALLBACK 1
#define TCPIP_THREAD_STACKSIZE 2048
#define TCPIP_THREAD_PRIO osPriorityNormal
#define TCPIP_MBOX_SIZE 6
#define SLIPIF_THREAD_STACKSIZE 1024
#define SLIPIF_THREAD_PRIO 3
#define DEFAULT_THREAD_STACKSIZE 2048
#define DEFAULT_THREAD_PRIO 3
#define DEFAULT_UDP_RECVMBOX_SIZE 6
#define DEFAULT_TCP_RECVMBOX_SIZE 6
#define DEFAULT_ACCEPTMBOX_SIZE 6
#define RECV_BUFSIZE_DEFAULT 2000000000
#define LWIP_STATS 0
#define CHECKSUM_GEN_IP 0
#define CHECKSUM_GEN_UDP 0
#define CHECKSUM_GEN_TCP 0
#define CHECKSUM_GEN_ICMP6 0
#define CHECKSUM_CHECK_IP 0
#define CHECKSUM_CHECK_UDP 0
#define CHECKSUM_CHECK_TCP 0
#define CHECKSUM_CHECK_ICMP6 0

---

Issue:
When running the project, I encounter a hard fault. I suspect this might be due to potential MPU region overlap or an incorrect memory allocation in D2. (For example, my MPU configuration for Region 1 covers 0x30000000–0x30008000, which might conflict with the reserved descriptors.)

My Questions:

1. How should I adjust the MPU configuration or memory allocation so that the lwIP heap (32232 bytes) in D2 does not overlap with the Ethernet DMA descriptors?
2. Is there a recommended strategy for relocating the Ethernet RX buffers to AXI SRAM (RAM_D1) while keeping the lwIP heap entirely in D2?
3. Are there any known issues with STM32CubeIDE v1.16.1 or FW H7 V1.11.2 that might contribute to this hard fault in the context of using microros over UDP?
4. What would be the best configuration for reliable, fast, and stable communication with a Micro-ROS agent on an Ubuntu 22.04 running ROS2 Humble?

Any guidance or suggestions would be greatly appreciated!

Thank you in advance.