MDK MIDDLEWARE: How to set MAC address at startup

Information in this knowledgebase article applies to:

• Keil MDK 5
• Middleware 7.0.0, and newer 

QUESTION

Usually, the MAC address of my target board can be configured and hardcoded in Net_Config_ETH_0. 

To implement our application into mass products, we have to set different unique MAC address for each board at the startup of the board.

How can I set a MAC address at startup of the board, instead of the one hardcoded in Net_Config_ETH_0?

RESOLUTION

Since Middleware 7.0.0 the function netIF_SetOption() is implemented that can setup MAC address.

In order to avoid the customized MAC address being overwritten by netInitialize() with the reconfigured MAC address in Net_Config_ETH_0.h, the function netIF_SetOption() should be called in the user callback function netETH_Notify(), when the Ethernet link is up. e.g.

#define MAC_DEFAULT "1E-30-6C-A2-45-5B"
char mac_addr[18];

void change_mac_addr(void){
  uint8_t buf[6];

  strncpy(mac_addr, MAC_DEFAULT, sizeof(mac_addr));

  if (netMAC_aton(mac_addr, buf) == true) {
    netIF_SetOption(NET_IF_CLASS_ETH | 0, netIF_OptionMAC_Address, buf, 6);
  }
}

void netETH_Notify (uint32_t if_num, netETH_Event event, uint32_t val) {

  switch (event) {
    case netETH_LinkDown:
      printf ("Link is down\n");
      break;
    case netETH_LinkUp:
      printf ("Link is up\n");

      change_mac_addr();

      break;
    case netETH_Wakeup:
      printf ("Wakeup frame received\n");
      break;
    case netETH_TimerAlarm:
      printf ("Timer alarm\n");
      break;
  }
}

Note, if the multicast bit is set in the new MAC address, netIF_SetOption will fail with netInvalidParameter.

MORE INFORMATION

• Refer to netIF_SetOption in the documentation of Network Common Interface API.

Last Reviewed: Friday, October 30, 2020