Hard fault to read internal EEPROM - STM32L011

[Kleber Lima da Silva]

Posted on January 10, 2017 at 15:27

Hi,

I am getting a hard fault while trying to read from the internal EEPROM (STM32L011), function:

uint8_t Read_EEPROM_Byte(uint32_t address)

{    uint8_t tmp = 0;

   address = address + 0x08080000;

   tmp = *(uint32_t*)address;

   return tmp;

}

How to solve this?

Thanks.

#stm32l0 #eeprom

[Jeroen3]

Posted on January 10, 2017 at 16:29

You're most likely performing a unaligned memory access.

 tmp = *(uint32_t*)address;

You are now trying to read 4 bytes from address into tmp. (of which the 3 most significant bytes will be truncated)

However, if address is uneven, eg:

0x*1, it's an illegal operation.

Remember, you can only access words on a word aligned address.

0x08080000

halfword / word aligned

0x08080002 halfword aligned

0x08080004 word aligned

...

Byte reads are always allowed by the core.

Some peripherals also limit the types of read/write to their memory region. 

This doesn't apply to reading here. It does to writing.

[Tesla DeLorean · Accepted solution]

Posted on January 10, 2017 at 17:24

Pro tip: When debugging Hard Faults, Look at the address it is complaining about, print it out, or look at it in the debugger.

The Cortex-M0 does not support unaligned read/write operations, and will also fault if you touch memory out of bounds. Use appropriate casting.

uint8_t Read_EEPROM_Byte(uint32_t address)
{
 uint8_t tmp = 0;
 address = address + 0x08080000;
 tmp = *(uint8_t*)address; // READ AS A BYTE
 return tmp;
}

uint8_t Read_EEPROM_Byte(uint32_t address)
{
 return(*(uint8_t*)(address + 0x08080000));
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[Kleber Lima da Silva]

Posted on January 10, 2017 at 17:36

Thanks Jeroen3 and Clive One.

Solved!

[Shay Eliyahu]

Posted on December 11, 2017 at 11:08

Hello Clive One,

what about to Unlock the EEPROM and lock it back??

[Shay Eliyahu]

Posted on December 11, 2017 at 11:09

Hello Kleber,

what about to Unlock the EEPROM and lock it back??

[Tesla DeLorean]

Posted on December 11, 2017 at 15:34

This post is from 11 months ago, a lot of the surrounding code is not shown, the cause of the fault in this case was the unaligned access. At the top level you might well need to lock/unlock the EEPROM, I'm sure the library has worked examples.