HardFault & DMA Descriptor Memory Issues in STM32F746G-Discovery Ethernet (LwIP) – Need Guidance for Cloud POST API Integration

[Abhishekvh76]

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Hello Community,

I am working on STM32F746G-Discovery and trying to send ADC sensor data to a cloud server using Ethernet.
Cloud API details:

URL: https://iot.hummingbirdtek.com/api/data
Method: POST
Content-Type: application/json

What I Have Done:

1. Enabled Ethernet (RMII) in CubeMX

2. Enabled LwIP, set static IP

3. Enabled ADC1, UART6 for debug

4. Generated code (AC6/GCC)

5. Added code to format JSON and send to cloud using http_post
   
   

   Issues I am facing:

   1) HardFault occurs after LwIP initialization

   The crash happens during:

   MX_LWIP_Init();
   netif_set_up();

   
   2) DMA Descriptor Memory Configuration Errors

   Compiler shows errors like:

   DMARxDscrTab memory out of range
   or
   aggregate value used where integer expected
   
   I suspect incorrect MPU/Alignment/Section placement for:

   ETH_DMADescTypeDef DMARxDscrTab[ETH_RX_DESC_CNT] __attribute__((section(".RxDecripSection")));
   ETH_DMADescTypeDef DMATxDscrTab[ETH_TX_DESC_CNT] __attribute__((section(".TxDecripSection")));

   
   I am not sure how this should be configured in CubeMX linker settings for STM32F746.
   
   

   3) Need guidance for correct .ioc Ethernet/LwIP configuration

   Specifically:

   • ETH clock settings

   • RMII pins required

   • LwIP static IP configuration

   • Required settings in lwipopts.h

   • Whether mbedTLS is required for HTTPS POST

   • If any official ST example project exists for STM32F746 + LwIP + HTTP POST
     
     

     4) Request

     Can someone please guide me with:

     ✔ Correct CubeMX IOC configuration steps
     ✔ Correct linker script placement for ETH DMA descriptors
     ✔ Any working example project (preferably F746G-DISCO)
     ✔ Any documents or references for fixing HardFault in LwIP init
     
     

     My Goal:

     Send ADC value as JSON to cloud through Ethernet:

     {
     "adc_value": 1024,
     "device": "stm32f746"
     }

     
     Any help, guidance, or example code will be greatly appreciated.

     Thank you!