ESP8266 Community Forum

- Sun Jan 10, 2016 3:20 pm #38441

If you read the SDK Guide about the RTC read/write functions it mentions being 4 byte blocks -

"Note: RTC memory is 4 bytes aligned for read and write operations. Parameter src_addr means block number(4 bytes per block)."

I don't completely understand the implications of that, but if you change your

Code: Select allbyte r[1];

variable definition in your sketch to be

Code: Select allbyte r[1] __attribute__((aligned(4)));

it seems to fix it.

Wow, thank you very much, that did indeed solve the problem. I don't understand i did not have problem with the other variable. Also i have not seen this attribute before in any examples. Did not know it existed.

- Mon Jan 11, 2016 4:57 am #38489

If you read the SDK Guide about the RTC read/write functions it mentions being 4 byte blocks -

"Note: RTC memory is 4 bytes aligned for read and write operations. Parameter src_addr means block number(4 bytes per block)."

I don't completely understand the implications of that, but if you change your

Code: Select allbyte r[1];

variable definition in your sketch to be

Code: Select allbyte r[1] __attribute__((aligned(4)));

it seems to fix it.

Wow, thank you very much, that did indeed solve the problem. I don't understand i did not have problem with the other variable. Also i have not seen this attribute before in any examples. Did not know it existed.

I think its a bit odd too. I saw this in one example once but can't remember where now, but have used the RTC memory a bunch of times and its worked fine without the aligned attribute. I wonder if theres a bug somewhere in the RTC read/write functions and this is just bypassing that rather than the correct fix.