ESP32 Forum

I need to store a Structure inside the NVS of ESP32, is it possible with the current APIs available somehow ??

Actual Problem is: I need to store the Alarms inside the ESP-32, which will be of following structure :

typedef struct
{

int minutes;
int hours;
int date ;

}Alarm ;


I will be storing multiple alarms inside the NVS & then fetching them at the startup.

Why do you *need* to store it as a struct? What happened when you tried that? What else have you tried?

I recommend you begin here: https://math.hawaii.edu/home/pdf/putnam ... olveIt.pdf

Seriously, Tom Meyers

Make your struct into a 64bit value which is supported by nvs. Hours and minutes don't need to be 32bit values.

Hi , Thanks for looking into my issue .

Are you suggesting me to convert the structure into byte & then saving that byte data into NVS?

At the Time of Retrieving, I cast that byte into the structure.

Like this : https://stackoverflow.com/questions/137 ... -to-struct

You can also try to convert to JSON and store as string, and convert back from JSON upon retrieval.

In the app I'm finishing up, I store a struct of about 1000 bytes in NVS. Just store it as a blob, and when you retrieve it, map it to a pointer to your struct.

mzimmers wrote: ↑

Wed Nov 14, 2018 8:47 pm

In the app I'm finishing up, I store a struct of about 1000 bytes in NVS. Just store it as a blob, and when you retrieve it, map it to a pointer to your struct.

That means update any field of a struct will update the whole blob.
Just wondering if that is a recommend way to use NVS.
BTW, the document says "NVS works best for storing many small values, rather than a few large values of type ‘string’ and ‘blob’."

Yeah, I read that too. My application rarely changes the values to the values in the struct (it's primarily used for startup configuration data), so I won't destroy the NVS by writing to it too frequently.

I wasn't trying to say it was the best way to go, merely that it was feasible. And in my app, the blob/struct is a private member of an object, so the setter routines include the write back to NVS. It's worked conveniently for me so far.

You can see example how store struct at https://github.com/SergeyKupavtsev/nvs_component