MDK MIDDLEWARE: Ethernet interface "Link Down"

Information in this knowledgebase article applies to:

• MDK v5.x
• Middleware Network Component v6.x, v7.x or newer versions

QUESTION

While debugging my program using Middleware network component library, from Network Component Viewer as shown below, as well as from network debug output, I can see the ethernet interface always has "Link Down" status. Therefore, the entire Middleware network stack doesn't work at all, i.e. no data packet can be sent or received.

What are the possible reasons/causes for such a link-down issue on the ethernet interface?

ANSWER

Typical reasons/causes for the ethernet interface staying in the link-down status are summarized as the following checklist:

1. Check if the RJ-45 ethernet cable is properly inserted/connected.
2. If one of the existing CMSIS PHY drivers in the CMSIS Driver pack is used in the project, make sure the one matching the ethernet PHY controller on your target device is correctly selected in Manage Run-Time Environment window in µVision.
3. If you have written your own CMSIS PHY driver for the ethernet PHY controller on your target device, make sure your CMSIS driver is implemented properly and works as expected, especially the CMSIS API functions GetLinkState() and GetLinkInfo(). The CMSIS-Driver_Validation Pack can help you to validate your CMSIS PHY driver implementation.
4. The ethernet interface, including pins configurations for data bus (MII or RMII) and management bus, needs to be configured properly in RTE_Device.h. More details about how to configure these pins can be found in user manual or reference guide of the MCU.
5. Read through Resource Requirements to make sure system resources and CMSIS-RTOS RTX resources are well allocated and configured for the Middleware network stack.
6. In the main() function, make sure necessary system peripherals as well as system clock are initialized correctly.
7. CMSIS-RTOS RTX kernel needs to be initialized properly before calling netInitialize(). Especially when CMSIS-RTOSv2 RTXv5 is used, where main() is not a RTX thread by default. In this case netInitialize() should be called in the "app_main" thread created from main(), where osKernelInitialize() has been called. Refer to RTX Migration Guide for more details.
8. The Ethernet driver in some cases might falsely identify that the link is down due to PHY layer read/write timeout. Increasing such a PHY layer read/write timeout might overcome it. e.g. if EMAC_STM32F4xx.c is used, the PHY timeout value can be increased from the line

   #define PHY_TIMEOUT         2U          /* PHY Register access timeout in ms  */
   

MORE INFORMATION

• Creating a Network Application
• GetLinkState
• GetLinkInfo

SEE ALSO

• MDK MIDDLEWARE: Network: How to check the PHY link status

Last Reviewed: Friday, August 3, 2018