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[STM32 NUCLEO] Init MAC address #2743

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Sep 24, 2016
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[STM32 NUCLEO] Init MAC address #2743

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28 changes: 28 additions & 0 deletions features/net/FEATURE_IPV4/lwip-interface/lwip-eth/arch/TARGET_STM/stm32xx_emac.c
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Original file line number Diff line number Diff line change
Expand Up @@ -448,3 +448,31 @@ void eth_arch_disable_interrupts(void)
{
NVIC_DisableIRQ(ETH_IRQn);
}

/** This returns a unique 6-byte MAC address, based on the device UID
* This function overrides hal/common/mbed_interface.c function
* @param mac A 6-byte array to write the MAC address
*/
void mbed_mac_address(char *mac) {
unsigned char ST_mac_addr[3] = {0x00, 0x80, 0xe1}; // default STMicro mac address
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Is this globally assigned to ST?

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yes, this is the official ST MAC address.
http://www.macmonster.co.uk/macoui=0080E1


// Read unic id
#if defined (TARGET_STM32F2)
uint32_t word0 = *(uint32_t *)0x1FFF7A10;
#elif defined (TARGET_STM32F4)
uint32_t word0 = *(uint32_t *)0x1FFF7A10;
#elif defined (TARGET_STM32F7)
uint32_t word0 = *(uint32_t *)0x1FF0F420;
#else
#error MAC address can not be derived from target unique Id
#endif

mac[0] = ST_mac_addr[0];
mac[1] = ST_mac_addr[1];
mac[2] = ST_mac_addr[2];
mac[3] = (word0 & 0x00ff0000) >> 16;
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how unique is the UUID and MSB, LSB? I tried this years ago and found that MSB, LSB didn't provide a great amount of randomness where in a room of 100 boards there would still be 2-5 conflicts. Ended up having to use CRC on the 128 to create 48 unique. Just some memories of bad times to avoid if not already accounted for.

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Unique Id is unique for each target :-)
But it's true it is 96 bits...
As I set the ST Id in the 3 first MAC bytes, I checked with boards around me, and using MSB looks quite OK to get some random Id...

mac[4] = (word0 & 0x0000ff00) >> 8;
mac[5] = (word0 & 0x000000ff);

return;
}